The Andes of Southern Peru - Geographical Reconnaissance along the Seventy-Third Meridian

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Title: The Andes of Southern Peru - Geographical Reconnaissance along the Seventy-Third Meridian
Author: Bowman, Isaiah, 1878-1950
Language: English
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[Illustration]

THE ANDES OF SOUTHERN
PERU

GEOGRAPHICAL RECONNAISSANCE ALONG THE
SEVENTY-THIRD MERIDIAN

ISAIAH BOWMAN
Director of the American Geographical Society

[Illustration: colophon]

PUBLISHED FOR
THE AMERICAN GEOGRAPHICAL SOCIETY
OF NEW YORK

HENRY HOLT AND COMPANY

1916

LATIN
AMERICA

HENRY HOLT AND COMPANY

THE QUINN & BODEN CO. PRESS
RAHWAY, N.J.

C. G. B.

PREFACE

The geographic work of the Yale Peruvian Expedition of 1911 was
essentially a reconnaissance of the Peruvian Andes along the 73rd
meridian. The route led from the tropical plains of the lower Urubamba
southward over lofty snow-covered passes to the desert coast at Camaná.
The strong climatic and topographic contrasts and the varied human life
which the region contains are of geographic interest chiefly because
they present so many and such clear cases of environmental control
within short distances. Though we speak of “isolated” mountain
communities in the Andes, it is only in a relative sense. The extreme
isolation felt in some of the world’s great deserts is here unknown. It
is therefore all the more remarkable when we come upon differences of
customs and character in Peru to find them strongly developed in spite
of the small distances that separate unlike groups of people.

My division of the Expedition undertook to make a contour map of the
two-hundred-mile stretch of mountain country between Abancay and the
Pacific coast, and a great deal of detailed geographic and physiographic
work had to be sacrificed to insure the completion of the survey. Camp
sites, forage, water, and, above all, strong beasts for the
topographer’s difficult and excessively lofty stations brought daily
problems that were always serious and sometimes critical. I was so
deeply interested in the progress of the topographic map that whenever
it came to a choice of plans the map and not the geography was first
considered. The effect upon my work was to distribute it with little
regard to the demands of the problems, but I cannot regret this in view
of the great value of the maps. Mr. Kai Hendriksen did splendid work in
putting through two hundred miles of plane-tabling in two months under
conditions of extreme difficulty. Many of his triangulation stations
ranged in elevation from 14,000 to nearly 18,000 feet, and the cold and
storms--especially the hailstorms of mid-afternoon--were at times most
severe.

It is also a pleasure to say that Mr. Paul Baxter Lanius, my assistant
on the lower Urubamba journey, rendered an invaluable service in
securing continuous weather records at Yavero and elsewhere, and in
getting food and men to the river party at a critical time. Dr. W. G.
Erving, surgeon of the Expedition, accompanied me on a canoe journey
through the lower gorge of the Urubamba between Rosalina and the mouth
of the Timpia, and again by pack train from Santa Ana to Cotahuasi. For
a time he assisted the topographer. It is due to his prompt surgical
assistance to various members of the party that the field work was
uninterrupted. He was especially useful when two of our river Indians
from Pongo de Mainique were accidentally shot. I have since been
informed by their _patrón_ that they were at work within a few months.

It is difficult to express the gratitude I feel toward Professor Hiram
Bingham, Director of the Expedition, first for the executive care he
displayed in the organization of the expedition’s plans, which left the
various members largely care-free, and second, for generously supplying
the time of various assistants in the preparation of results. I have
enjoyed so many facilities for the completion of the work that at least
a year’s time has been saved thereby. Professor Bingham’s enthusiasm for
pioneer field work was in the highest degree stimulating to every member
of the party. Furthermore, it led to a determination to complete at all
hazards the original plans.

Finally, I wish gratefully to acknowledge the expert assistance of Miss
Gladys M. Wrigley, of the editorial staff of the American Geographical
Society, who prepared the climatic tables, many of the miscellaneous
data related thereto, and all of the curves in Chapter X. Miss Wrigley
also assisted in the revision of Chapters IX and X and in the correction
of the proof. Her eager and in the highest degree faithful assistance in
these tasks bespeaks a true scientific spirit.

ISAIAH BOWMAN.

SPECIAL ACKNOWLEDGMENTS FOR ILLUSTRATIONS

Fig. 28. Photograph by H. L. Tucker, Engineer, Yale Peruvian Expedition
of 1911.

Fig. 43. Photograph by H. L. Tucker.

Fig. 44. Photograph by Professor Hiram Bingham.

Figs. 136, 139, 140. Data for hachured sketch maps, chiefly from
topographic sheets by A. H. Bumstead, Topographer to Professor Bingham’s
Peruvian Expeditions of 1912 and 1914.

CONTENTS

PART I

HUMAN GEOGRAPHY

CHAPTER PAGE

I. THE REGIONS OF PERU 1

II. THE RAPIDS AND CANYONS OF THE URUBAMBA 8

III. THE RUBBER FORESTS 22

IV. THE FOREST INDIANS 36

V. THE COUNTRY OF THE SHEPHERDS 46

VI. THE BORDER VALLEYS OF THE EASTERN ANDES 68

VII. THE GEOGRAPHIC BASIS OF REVOLUTIONS AND OF HUMAN
CHARACTER IN THE PERUVIAN ANDES 88

VIII. THE COASTAL DESERT 110

IX. CLIMATOLOGY OF THE PERUVIAN ANDES 121

X. METEOROLOGICAL RECORDS FROM THE PERUVIAN ANDES 157

PART II

PHYSIOGRAPHY OF THE PERUVIAN ANDES

XI. THE PERUVIAN LANDSCAPE 183

XII. THE WESTERN ANDES: THE MARITIME CORDILLERA OR CORDILLERA
OCCIDENTAL 199

XIII. THE EASTERN ANDES: THE CORDILLERA VILCAPAMPA 204

XIV. THE COASTAL TERRACES 225

XV. PHYSIOGRAPHIC AND GEOLOGIC DEVELOPMENT 233

XVI. GLACIAL FEATURES 274

APPENDIX A. SURVEY METHODS EMPLOYED IN THE CONSTRUCTION OF
THE SEVEN ACCOMPANYING TOPOGRAPHIC SHEETS 315

APPENDIX B. FOSSIL DETERMINATIONS 321

APPENDIX C. KEY TO PLACE NAMES 324

INDEX 327

TOPOGRAPHIC SHEETS

Camaná Quadrangle 114

Aplao " 120

Coropuna " 188

Cotahuasi " 192

La Cumbre " 202

Antabamba " 282

Lambrama "

PART I

HUMAN GEOGRAPHY

CHAPTER I

THE REGIONS OF PERU

Let four Peruvians begin this book by telling what manner of country
they live in. Their ideas are provincial and they have a fondness for
exaggerated description: but, for all that, they will reveal much that
is true because they will at least reveal themselves. Their opinions
reflect both the spirit of the toiler on the land and the outlook of the
merchant in the town in relation to geography and national problems.
Their names do not matter; let them stand for the four human regions of
Peru, for they are in many respects typical men.

THE FOREST DWELLER

One of them I met at a rubber station on the lower Urubamba River.[1] He
helped secure my canoe, escorted me hospitably to his hut, set food and
drink before me, and talked of the tropical forest, the rubber business,
the Indians, the rivers, and the trails. In his opinion Peru was a land
of great forest resources. Moreover, the fertile plains along the river
margins might become the sites of rich plantations. The rivers had many
fish and his garden needed only a little cultivation to produce an
abundance of food. Fruit trees grew on every hand. He had recently
married the daughter of an Indian chief.

Formerly he had been a missionary at a rubber station on the Madre de
Dios, where the life was hard and narrow, and he doubted if there were
any real converts. Himself the son of an Englishman and a Chilean woman,
he found, so he said, that a missionary’s life in the rubber forest was
intolerable for more than a few years. Yet he had no fault to find with
the religious system of which he had once formed a part; in fact he had
still a certain curious mixed loyalty to it. Before I left he gave me a
photograph of himself and said with little pride and more sadness that
perhaps I would remember him as a man that had done some good in the
world along with much that might have been better.

We shall understand our interpreter better if we know who his associates
were. He lived with a Frenchman who had spent several years in Africa as
a soldier in the “Foreign Legion.” If you do not know what that means,
you have yet all the pleasure of an interesting discovery. The Frenchman
had reached the station the year before quite destitute and clad only in
a shirt and a pair of trousers. A day’s journey north lived a young
half-breed--son of a drunken father and a Machiganga woman, who cheated
me so badly when I engaged Indian paddlers that I should almost have
preferred that he had robbed me. Yet in a sense he had my life in his
hands and I submitted. A German and a native Peruvian ran a rubber
station on a tributary two days’ journey from the first. It will be
observed that the company was mixed. They were all Peruvians, but of a
sort not found in such relative abundance elsewhere. The defeated and
the outcast, as well as the pioneer, go down eventually to the hot
forested lands where men are forgotten.

While he saw gold in every square mile of his forested region, my
clerical friend saw misery also. The brutal treatment of the Indians by
the whites of the Madre de Dios country he could speak of only as a man
reviving a painful memory. The Indians at the station loved him
devotedly. There was only justice and kindness in all his dealings.
Because he had large interests to look after, he knew all the members of
the tribe, and his word was law in no hackneyed sense. A kindlier man
never lived in the rubber forest. His influence as a high-souled man of
business was vastly greater than as a missionary in this frontier
society. He could daily illustrate by practical example what he had
formerly been able only to preach.

[Illustration: Fig. 1--Tropical vegetation, clearing on the river bank
and rubber station at Pongo de Mainique. The pronounced scarp on the
northeastern border of the Andes is seen in the right background.]

[Illustration: Fig. 2--Pushing a heavy dugout against the current in the
rapids below Pongo de Mainique. The indian boy and his father in the
canoe had been accidentally shot.]

[Illustration: Fig. 3--From the sugar cane, Urubanba Valley, at Colpani.
On the northeastern border of the Cordillera Vilcapampa looking
upstream. In the extreme background and thirteen sixteens of an inch
from the top of the picture is the sharp peak of Salcantay. Only the
lower end of the more open portion of the Canyon of Torontoy is here
shown. There is a field of sugar cane in the foreground and the valley
trail is shown on the opposite side of the river.]

He thought the life of the Peruvian cities debasing. The coastal
valleys were small and dry and the men who lived there were crowded and
poor (sic). The plateau was inhabited by Indians little better than
brutes. Surely I could not think that the fine forest Indian was lower
than the so-called civilized Indian of the plateau. There was plenty of
room in the forest; and there was wealth if you knew how to get at it.
Above all you were far from the annoying officials of the government,
and therefore could do much as you pleased so long as you paid your
duties on rubber and did not wantonly kill too many Indians.

For all his kindly tolerance of men and conditions he yet found fault
with the government. “They” neglected to build roads, to encourage
colonization, and to lower taxes on the forest products, which were
always won at great risk. Nature had done her part well--it was only
government that hindered. Moreover, the forested region was the land of
the future. If Peru was to be a great nation her people would have to
live largely upon the eastern plains. Though others spoke of “going in”
and “coming out” of the rubber country as one might speak of entering
and leaving a dungeon, he always spoke of it as home. Though he now
lived in the wilderness he hoped to see the day when plantations covered
the plains. A greater Peru and the forest were inseparable ideas to him.

THE EASTERN VALLEY PLANTER

My second friend lived in one of the beautiful mountain valleys of the
eastern Andes. We walked through his clean cacao orchards and cane
fields. Like the man in the forest, he believed in the thorough
inefficiency of the government; otherwise why were there no railways for
the cheaper transportation of the valley products, no dams for the
generation of power and the storage of irrigation water, not even roads
for mule carts? Had the government been stable and efficient there would
now be a dense population in the eastern valleys. Revolutions were the
curse of these remote sections of the country. The ne’er-do-wells became
generals. The loafer you dismissed today might demand ten thousand
dollars tomorrow or threaten to destroy your plantation. The government
troops might come to help you, but they were always too late.

For this one paid most burdensome taxes. Lima profited thereby, not the
valley planters. The coast people were the favored of Peru anyhow. They
had railroads, good steamer service, public improvements at government
expense, and comparatively light taxes. If the government were impartial
the eastern valleys also would have railways and a dense population. Who
could tell? Perhaps the capital city might be here. Certainly it was
better to have Lima here than on the coast where the Chileans might at
any time take it again. The blessings of the valleys were both rich and
manifold. Here was neither a cold plateau nor the hot plains, but
fertile valleys with a vernal climate.

We talked of much else, but our conversation had always the pioneer
flavor. And though an old man he saw always the future Peru growing
wonderfully rich and powerful as men came to recognize and use the
resources of the eastern valleys. This too was the optimism of the
pioneer. Once started on that subject he grew eloquent. He was
provincial but he was also intensely patriotic. He never missed an
opportunity to impress upon his guests that a great state would arise
when people and rulers at last recognized the wealth of eastern Peru.

THE HIGHLAND SHEPHERD

The people who live in the lofty highlands and mountains of Peru have
several months of real winter weather despite their tropical latitude.
In the midst of a snowstorm in the Maritime Cordillera I met a solitary
traveler bound for Cotahuasi on the floor of a deep canyon a day’s
journey toward the east. It was noon and we halted our pack trains in
the lee of a huge rock shelter to escape the bitter wind that blew down
from the snow-clad peaks of Solimana. Men who follow the same trails are
fraternal. In a moment we had food from our saddle-bags spread on the
snow under the corner of a _poncho_ and had exchanged the best in each
other’s collection as naturally as friends exchange greetings. By the
time I had told him whence and why in response to his inevitable
questions we had finished the food and had gathered a heap of _tola_
bushes for a fire. The _arriero_ (muleteer) brought water from a spring
in the hollow below us. Though the snow thickened, the wind fell. We
were comfortable, even at 16,000 feet, and called the place “The
Salamanca Club.” Then I questioned him, and this is what he said:

“I live in the deep valley of Cotahuasi, but my lands lie chiefly up
here on the plateau. My family has held title to this _puna_ ever since
the Wars of Liberation, except for a few years after one of our early
revolutions. I travel about a great deal looking after my flocks. Only
Indians live up here. Away off yonder beyond that dark gorge is a group
of their huts, and on the bright days of summer you may see their sheep,
llamas, and alpacas up here, for on the floors of the watered valleys
that girdle these volcanoes there are more tender grasses than grow on
this _despoblado_. I give them corn and barley from my irrigated fields
in the valley; they give me wool and meat. The alpaca wool is most
valuable. It is hard to get, for the alpaca requires short grasses and
plenty of water, and you see there is only coarse tufted ichu grass
about us, and there are no streams. It is all right for llamas, but
alpacas require better forage.

“No one can imagine the poverty and ignorance of these mountain
shepherds. They are filthier than beasts. I have to watch them
constantly or they would sell parts of the flocks, which do not belong
to them, or try to exchange the valuable alpaca wool for coca leaves in
distant towns. They are frequently drunk.”

“But where do they get the drink?” I asked. “And what do you pay them?”

“Oh, the drink is chiefly imported alcohol, and also _chicha_ made from
corn. They insist on having it, and do better when I bring them a little
now and then. They get much more from the dealers in the towns. As for
pay, I do not pay them anything in money except when they bring meat to
the valley. Then I give them a few _reales_ apiece for the sheep and a
little more for the llamas. The flocks all belong to me really, but of
course the poor Indian must have a little money. Besides, I let him have
a part of the yearly increase. It is not much, but he has always lived
this way and I suppose that he is contented after a fashion.”

Then he became eager to tell what wealth the mountains contained in soil
and climate if only the right grasses were introduced by the government.

“Here, before us, are vast _punas_ almost without habitations. If the
officials would bring in hardy Siberian grasses these lava-covered
plateaus might be carpeted with pasture. There would be villages here
and there. The native Indians easily stand the altitude. This whole
Cordillera might have ten times as many people. Why does the government
bother about concessions in the rubber forests and roads to the eastern
valleys when there are these vast tracts only requiring new seeds to
develop into rich pastures? The government could thus greatly increase
its revenues because there is a heavy tax on exported wool.”

Thus he talked about the bleak Cordillera until we forgot the pounding
of our hearts and our frequent gasps for breath on account of the
altitude. His rosy picture of a well-populated highland seemed to bring
us down nearer sea level where normal folks lived. To the Indians the
altitude is nothing. It has an effect, but it is slight; at any rate
they manage to reproduce their kind at elevations that would kill a
white mother. If alcohol were abolished and better grasses introduced,
these lofty pastures might indeed support a much larger population. The
sheep pastures of the world are rapidly disappearing before the march of
the farmer. Here, well above the limit of cultivation, is a permanent
range, one of the great as well as permanent assets of Peru.

THE COASTAL PLANTER

The man from the deep Majes Valley in the coastal desert rode out with
me through cotton fields as rich and clean as those of a Texas
plantation. He was tall, straight-limbed, and clear-eyed--one of the
energetic younger generation, yet with the blood of a proud old family.
We forded the river and rode on through vineyards and fig orchards
loaded with fruit. His manner became deeply earnest as he pictured the
future of Peru, when her people would take advantage of scientific
methods and use labor-saving machinery. He said that the methods now in
use were medieval, and he pointed to a score of concrete illustrations.
Also, here was water running to waste, yet the desert was on either
hand. There should be dams and canals. Every drop of water was needed.
The population of the valley could be easily doubled.

[Illustration: FIG. 4--Large ground moss--so-called _yareta_--used for
fuel. It occurs in the zone of Alpine vegetation and is best developed
in regions where the snowline is highest. The photograph represents a
typical occurrence between Cotahuasi and Salamanca, elevation 16,000
feet (4,880 m.). The snowline is here at 17,500 feet (5,333 m.). In the
foreground is the most widely distributed _tola_ bush, also used for
fuel.]

[Illustration: FIG. 5.--Expedition’s camp near Lamgrama, 15,500 feet
(4,720 m.), after a snowstorm The location is midway in the pasture
zone.]

[Illustration: FIG. 6--Irrigated Chili Valley on the outskirts of
Arequipa. The lower slopes of El Misti are in the left background. The
_Alto de los Huesos_ or Plateau of Bones lies on the farther side of the
valley.]

[Illustration: FIG. 7--Crossing the highest pass (Chuquito) in the
Cordillera Vilcapampa, 14,500 feet (4,420 m.). Grazing is here carried
on up to the snowline.]

Capital was lacking but there was also lacking energy among the people.
Slipshod methods brought them a bare living and they were too easily
contented. Their standards of life should be elevated. Education was
still for the few, and it should be universal. A new spirit of progress
was slowly developing--a more general interest in public affairs, a
desire to advance with the more progressive nations of South
America,--and when it had reached its culmination there would be no
happier land than coastal Peru, already the seat of the densest
populations and the most highly cultivated fields.

* * * * *

These four men have portrayed the four great regions of Peru--the
lowland plains, the eastern mountain valleys, the lofty plateaus, and
the valley oases of the coast. This is not all of Peru. The mountain
basins have their own peculiar qualities and the valley heads of the
coastal zone are unlike the lower valleys and the plateau on either
hand. Yet the chief characteristics of the country are set forth with
reasonable fidelity in these individual accounts. Moreover the spirit of
the Peruvians is better shown thereby than their material resources. If
this is not Peru, it is what the Peruvians think is Peru, and to a high
degree a man’s country is what he thinks it is--at least it is little
more to him.

CHAPTER II

THE RAPIDS AND CANYONS OF THE URUBAMBA

Among the scientifically unexplored regions of Peru there is no other so
alluring to the geographer as the vast forested realm on the eastern
border of the Andes. Thus it happened that within two weeks of our
arrival at Cuzco we followed the northern trail to the great canyon of
the Urubamba (Fig. 8), the gateway to the eastern valleys and the
lowland plains of the Amazon. It is here that the adventurous river,
reënforced by hundreds of mountain-born tributaries, finally cuts its
defiant way through the last of its great topographic barriers. More
than seventy rapids interrupt its course; one of them, at the mouth of
the Sirialo, is at least a half-mile in length, and long before one
reaches its head he hears its roaring from beyond the forest-clad
mountain spurs.

The great bend of the Urubamba in which the line of rapids occurs is one
of the most curious hydrographic features in Peru. The river suddenly
changes its general northward course and striking south of west flows
nearly fifty miles toward the axis of the mountains, where, turning
almost in a complete circle, it makes a final assault upon the eastern
mountain ranges. Fifty miles farther on it breaks through the long
sharp-crested chain of the Front Range of the Andes in a splendid gorge
more than a half-mile deep, the famous _Pongo de Mainique_ (Fig. 9).

Our chief object in descending the line of rapids was to study the
canyon of the Urubamba below Rosalina and to make a topographic sketch
map of it. We also wished to know what secrets might be gathered in this
hitherto unexplored stretch of country, what people dwelt along its
banks, and if the vague tales of deserted towns and fugitive tribes had
any basis in fact.

[Illustration: FIG. 8--Sketch map showing the route of the Yale-Peruvian
Expedition of 1911 down the Urubamba Valley, together with the area of
the main map and the changes in the delineation of the bend of the
Urubamba resulting from the surveys of the Expedition. Based on the
“Mapa que comprende las ultimas exploraciones y estudios verificados
desde 1900 hasta 1906,” 1:1,000,000, Bol. Soc. Geogr. Lima, Vol. 25, No.
3, 1909. For details of the trail from Rosalina to Pongo de Mainique see
“Plano de las Secciones y Afluentes del Rio Urubamba: 1902-1904,” scale
1:150,000 by Luis M. Robledo in Bol. Soc. Geogr. Lima, Vol. 25, No. 4,
1909. Only the lower slopes of the long mountain spurs can be seen from
the river; hence only in a few places could observations be made on the
topography of distant ranges. Paced distances of a half mile at
irregular intervals were used for the estimation of longer distances.
Directions were taken by compass corrected for magnetic deviation as
determined on the seventy-third meridian (See Appendix A). The position
of Rosalina on Robledo’s map was taken as a base.]

We could gather almost no information as to the nature of the river
except from the report of Major Kerbey, an American, who, in 1897,
descended the last twenty miles of the one hundred we proposed to
navigate. He pronounced the journey more hazardous than Major Powell’s
famous descent of the Grand Canyon in 1867--an obvious exaggeration. He
lost his canoe in a treacherous rapid, was deserted by his Indian
guides, and only after a painful march through an all but impassable
jungle was he finally able to escape on an abandoned raft. Less than a
dozen have ventured down since Major Kerbey’s day. A Peruvian mining
engineer descended the river a few years ago, and four Italian traders a
year later floated down in rafts and canoes, losing almost all of their
cargo. For nearly two months they were marooned upon a sand-bar waiting
for the river to subside. At last they succeeded in reaching
Mulanquiato, an Indian settlement and plantation owned by Pereira, near
the entrance to the last canyon. Their attempted passage of the worst
stretch of rapids resulted in the loss of all their rubber cargo, the
work of a year. Among the half dozen others who have made the
journey--Indians and slave traders from down-river rubber posts--there
is no record of a single descent without the loss of at least one canoe.

To reach the head of canoe navigation we made a two weeks’ muleback
journey north of Cuzco through the steep-walled granite Canyon of
Torontoy, and to the sugar and cacao plantations of the middle Urubamba,
or Santa Ana Valley, where we outfitted. At Echarati, thirty miles
farther on, where the heat becomes more intense and the first patches of
real tropical forest begin, we were obliged to exchange our beasts for
ten fresh animals accustomed to forest work and its privations. Three
days later we pitched our tent on the river bank at Rosalina, the last
outpost of the valley settlements. As we dropped down the steep mountain
slope before striking the river flood plain, we passed two half-naked
Machiganga Indians perched on the limbs of a tree beside the trail, our
first sight of members of a tribe whose territory we had now entered.
Later in the day they crossed the river in a dugout, landed on the
sand-bar above us, and gathered brush for the nightly fire, around which
they lie wrapped in a single shirt woven from the fiber of the wild
cotton.

[Illustration: FIG. 9--The upper entrance to the Pongo de Mainique,
where the Urubamba crosses the Front Range of the Andes in a splendid
gateway 4,000 feet deep. The river is broken by an almost continuous
line of rapids.]

[Illustration: FIG. 10--The lower half of a two-thousand-foot cliff,
granite Canyon of Torontoy, Urubamba Valley. The wall is developed
almost entirely along joint planes. It is here that the Urubamba River
crosses the granite axis of the Cordillera Vilcapampa, the easternmost
system of the Andes of southern Peru. Compare also Figs. 144 and 145.]

[Illustration: FIG. 11--A temporary shelter-hut on a sand-bar near the
great bend of the Urubamba (see map, Fig. 8). The Machiganga Indians use
these cane shelters during the fishing season, when the river is low.]

[Illustration: FIG. 12--Thirty-foot canoe in a rapid above Pongo de
Mainique.]

Rosalina is hardly more than a name on the map and a camp site on the
river bank. Some distance back from the left bank of the river is a
sugar plantation, whose owner lives in the cooler mountains, a day’s
journey away; on the right bank is a small clearing planted to sugar
cane and yuca, and on the edge of it is a reed hut sheltering three
inhabitants, the total population of Rosalina. The owner asked our
destination, and to our reply that we should start in a few days for
Pongo de Mainique he offered two serious objections. No one thought of
arranging so difficult a journey in less than a month, for canoe and
Indians were difficult to find, and the river trip was dangerous.
Clearly, to start without the loss of precious time would require
unusual exertion. We immediately despatched an Indian messenger to the
owner of the small hacienda across the river while one of our peons
carried a second note to a priest of great influence among the forest
Indians, Padre Mendoza, then at his other home in the distant mountains.

The answer of Señor Morales was his appearance in person to offer the
hospitality of his home and to assist us in securing canoe and oarsmen.
To our note the Padre, from his hill-top, sent a polite answer and the
offer of his large canoe if we would but guarantee its return. His
temporary illness prevented a visit to which we had looked forward with
great interest.

The morning after our arrival I started out on foot in company with our
_arriero_ in search of the Machigangas, who fish and hunt along the
river bank during the dry season and retire to their hill camps when the
heavy rains begin. We soon left the well-beaten trail and, following a
faint woodland path, came to the river bank about a half day’s journey
below Rosalina. There we found a canoe hidden in an overhanging arch of
vines, and crossing the river met an Indian family who gave us further
directions. Their vague signs were but dimly understood and we soon
found ourselves in the midst of a _carrizo_ (reed) swamp filled with
tall bamboo and cane and crossed by a network of interlacing streams. We
followed a faint path only to find ourselves climbing the adjacent
mountain slopes away from our destination. Once again in the swamp we
had literally to cut our way through the thick cane, wade the numberless
brooks, and follow wild animal trails until, late in the day, famished
and thirsty, we came upon a little clearing on a sand-bar, the hut of La
Sama, who knew the Machigangas and their villages.

After our long day’s work we had fish and yuca, and water to which had
been added a little raw cane sugar. Late at night La Sama returned from
a trip to the Indian villages down river. He brought with him a
half-dozen Machiganga Indians, boys and men, and around the camp fire
that night gave us a dramatic account of his former trip down river. At
one point he leaped to his feet, and with an imaginary pole shifted the
canoe in a swift rapid, turned it aside from imminent wreck, and
shouting at the top of his voice over the roar of the water finally
succeeded in evading what he had made seem certain death in a whirlpool.
We kept a fire going all night long for we slept upon the ground without
a covering, and, strange as it may appear, the cold seemed intense,
though the minimum thermometer registered 59° F. The next morning the
whole party of ten sunned themselves for nearly an hour until the flies
and heat once more drove them to shelter.

Returning to camp next day by a different route was an experience of
great interest, because of the light it threw on hidden trails known
only to the Indian and his friends. Slave raiders in former years
devastated the native villages and forced the Indian to conceal his
special trails of refuge. At one point we traversed a cliff seventy-five
feet above the river, walking on a narrow ledge no wider than a man’s
foot. At another point the dim trail apparently disappeared, but when we
had climbed hand over hand up the face of the cliff, by hanging vines
and tree roots, we came upon it again. Crossing the river in the canoe
we had used the day before, we shortened the return by wading the swift
Chirumbia waist-deep, and by crawling along a cliff face for nearly an
eighth of a mile. At the steepest point the river had so under-cut the
face that there was no trail at all, and we swung fully fifteen feet
from one ledge to another, on a hanging vine high above the river.

After two days’ delay we left Rosalina late in the afternoon of August
7. My party included several Machiganga Indians, La Sama, and Dr. W. G.
Erving, surgeon of the expedition. Mr. P. B. Lanius, Moscoso (the
_arriero_), and two peons were to take the pack train as far as possible
toward the rubber station at Pongo de Mainique where preparations were
to be made for our arrival. At the first rapid we learned the method of
our Indian boatmen. It was to run the heavy boat head on into shallow
water at one side of a rapid and in this way “brake” it down stream.
Heavily loaded with six men, 200 pounds of baggage, a dog, and supplies
of yuca and sugar cane our twenty-five foot dugout canoe was as rigid as
a steamer, and we dropped safely down rapid after rapid until long after
dark, and by the light of a glorious tropical moon we beached our craft
in front of La Sama’s hut at the edge of the cane swamp.

Here for five days we endured a most exasperating delay. La Sama had
promised Indian boatmen and now said none had yet been secured. Each day
Indians were about to arrive, but by nightfall the promise was broken
only to be repeated the following morning. To save our food supply--we
had taken but six days’ provisions--we ate yuca soup and fish and some
parched corn, adding to this only a little from our limited stores. At
last we could wait no longer, even if the map had to be sacrificed to
the work of navigating the canoe. Our determination to leave stirred La
Sama to final action. He secured an assistant named Wilson and embarked
with us, planning to get Indians farther down river or make the journey
himself.

On August 12, at 4.30 P.M., we entered upon the second stage of the
journey. As we shot down the first long rapid and rounded a wooded bend
the view down river opened up and gave us our first clear notion of the
region we had set out to explore. From mountain summits in the clouds
long trailing spurs descend to the river bank. In general the slopes are
smooth-contoured and forest-clad from summit to base; only in a few
places do high cliffs diversify the scenery. The river vista everywhere
includes a rapid and small patches of _playa_ or flood plain on the
inside of the river curves. Although a true canyon hems in the river at
two celebrated passes farther down, the upper part of the river flows
in a somewhat open valley of moderate relief, with here and there a
sentinel-like peak next the river.

A light shower fell at sunset, a typical late-afternoon downpour so
characteristic of the tropics. We landed at a small encampment of
Machigangas, built a fire against the scarred trunk of a big palm, and
made up our beds in the open, covering them with our rubber ponchos. Our
Indian neighbors gave us yuca and corn, but their neighborliness went no
further, for when our boatmen attempted to sleep under their roofs they
drove them out and fastened as securely as possible the shaky door of
their hut.

All our efforts to obtain Indians, both here and elsewhere, proved
fruitless. One excuse after another was overcome; they plainly coveted
the trinkets, knives, machetes, muskets, and ammunition that we offered
them; and they appeared to be friendly enough. Only after repeated
assurances of our friendship could we learn the real reason for their
refusal. Some of them were escaped rubber pickers that had been captured
by white raiders several years before, and for them a return to the
rubber country meant enslavement, heavy floggings, and separation from
their numerous wives. The hardships they had endured, their final
escape, the cruelty of the rubber men, and the difficult passage of the
rapids below were a set of circumstances that nothing in our list of
gifts could overcome. My first request a week before had so sharpened
their memory that one of them related the story of his wrongs, a recital
intensely dramatic to the whole circle of his listeners, including
myself. Though I did not understand the details of his story, his tones
and gesticulations were so effective that they held me as well as his
kinsmen of the woods spellbound for over an hour.

It is appalling to what extent this great region has been depopulated by
the slave raiders and those arch enemies of the savage, smallpox and
malaria. At Rosalina, over sixty Indians died of malaria in one year;
and only twenty years ago seventy of them, the entire population of the
Pongo, were swept away by smallpox. For a week we passed former camps
near small abandoned clearings, once the home of little groups of
Machigangas. Even the summer shelter huts on the sand-bars, where the
Indians formerly gathered from their hill homes to fish, are now almost
entirely abandoned. Though our men carefully reconnoitered each one for
fear of ambush, the precaution was needless. Below the Coribeni the
Urubamba is a great silent valley. It is fitted by Nature to support
numerous villages, but its vast solitudes are unbroken except at night,
when a few families that live in the hills slip down to the river to
gather yuca and cane.

By noon of the second day’s journey we reached the head of the great
rapid at the mouth of the Sirialo. We had already run the long Coribeni
rapid, visited the Indian huts at the junction of the big Coribeni
tributary, exchanged our canoe for a larger and steadier one, and were
now to run one of the ugliest rapids of the upper river. The rapid is
formed by the gravel masses that the Sirialo brings down from the
distant Cordillera Vilcapampa. They trail along for at least a
half-mile, split the river into two main currents and nearly choke the
mouth of the tributary. For almost a mile above this great barrier the
main river is ponded and almost as quiet as a lake.

We let our craft down this rapid by ropes, and in the last difficult
passage were so roughly handled by our almost unmanageable canoe as to
suffer from several bad accidents. All of the party were injured in one
way or another, while I suffered a fracture sprain of the left foot that
made painful work of the rest of the river trip.

At two points below Rosalina the Urubamba is shut in by steep mountain
slopes and vertical cliffs. Canoe navigation below the Sirialo and
Coribeni rapids is no more hazardous than on the rapids of our northern
rivers, except at the two “pongos” or narrow passages. The first occurs
at the sharpest point of the abrupt curve shown on the map; the second
is the celebrated Pongo de Mainique. In these narrow passages in time of
high water there is no landing for long stretches. The bow paddler
stands well forward and tries for depth and current; the stern paddler
keeps the canoe steady in its course. When paddlers are in agreement
even a heavy canoe can be directed into the most favorable channels.
Our canoemen were always in disagreement, however, and as often as not
we shot down rapids at a speed of twenty miles an hour, broadside on,
with an occasional bump on projecting rocks or boulders whose warning
ordinary boatmen would not let go unheeded.

The scenery at the great bend is unusually beautiful. The tropical
forest crowds the river bank, great cliffs rise sheer from the water’s
edge, their faces overhung with a trailing drapery of vines, and in the
longer river vistas one may sometimes see the distant heights of the
Cordillera Vilcapampa. We shot the long succession of rapids in the
first canyon without mishap, and at night pitched our tent on the edge
of the river near the mouth of the Manugali.

From the sharp peak opposite our camp we saw for the first time the
phenomenon of cloud-banners. A light breeze was blowing from the western
mountains and its vapor was condensed into clouds that floated down the
wind and dissolved, while they were constantly forming afresh at the
summit. In the night a thunderstorm arose and swept with a roar through
the vast forest above us. The solid canopy of the tropical forest fairly
resounded with the impact of the heavy raindrops. The next morning all
the brooks from the farther side of the river were in flood and the
river discolored. When we broke camp the last mist wraiths of the storm
were still trailing through the tree-tops and wrapped about the peak
opposite our camp, only parting now and then to give us delightful
glimpses of a forest-clad summit riding high above the clouds.

The alternation of deeps and shallows at this point in the river and the
well-developed canyon meanders are among the most celebrated of their
kind in the world. Though shut in by high cliffs and bordered by
mountains the river exhibits a succession of curves so regular that one
might almost imagine the country a plain from the pattern of the
meanders. The succession of smooth curves for a long distance across
existing mountains points to a time when a lowland plain with moderate
slopes drained by strongly meandering rivers was developed here. Uplift
afforded a chance for renewed down-cutting on the part of all the
streams, and the incision of the meanders. The present meanders are, of
course, not the identical ones that were formed on the lowland plain;
they are rather their descendants. Though they still retain their
strongly curved quality, and in places have almost cut through the
narrow spurs between meander loops, they are not smooth like the
meanders of the Mississippi. Here and there are sharp irregular turns
that mar the symmetry of the larger curves. The alternating bands of
hard and soft rock have had a large part in making the course more
irregular. The meanders have responded to the rock structure. Though
regular in their broader features they are irregular and deformed in
detail.

Deeps and shallows are known in every vigorous river, but it is seldom
that they are so prominently developed as in these great canyons. At one
point in the upper canyon the river has been broadened into a lake two
or three times the average width of the channel and with a scarcely
perceptible current; above and below the “laguna,” as the boatmen call
it, are big rapids with beds so shallow that rocks project in many
places. In the Pongo de Mainique the river is at one place only fifty
feet wide, yet so deep that there is little current. It is on the banks
of the quiet stretches that the red forest deer grazes under leafy
arcades. Here, too, are the boa-constrictor trails several feet wide and
bare like a roadway. At night the great serpents come trailing down to
the river’s edge, where the red deer and the wildcat, or so-called
“tiger,” are their easy prey.

It is in such quiet stretches that one also finds the vast colonies of
water skippers. They dance continuously in the sun with an incessant
motion from right to left and back again. Occasionally one dances about
in circles, then suddenly darts through the entire mass, though without
striking his equally erratic neighbors. An up-and-down motion still
further complicates the effect. It is positively bewildering to look
intently at the whirling multitude and try to follow their complicated
motions. Every slight breath of wind brings a shock to the organization
of the dance. For though they dance only in the sun, their favorite
places are the sunny spots in the shade near the bank, as beneath an
overhanging tree. When the wind shakes the foliage the mottled pattern
of shade and sunlight is confused, the dance slows down, and the dancers
become bewildered. In a storm they seek shelter in the jungle. The hot,
quiet, sunlit days bring out literally millions of these tiny creatures.

One of the longest deeps in the whole Urubamba lies just above the Pongo
at Mulanquiato. We drifted down with a gentle current just after sunset.
Shrill whistles, like those of a steam launch, sounded from either bank,
the strange piercing notes of the lowland cicada, _cicada tibicen_. Long
decorated canoes, better than any we had yet seen, were drawn up in the
quiet coves. Soon we came upon the first settlement. The owner, Señor
Pereira, has gathered about him a group of Machigangas, and by marrying
into the tribe has attained a position of great influence among the
Indians. Upon our arrival a gun was fired to announce to his people that
strangers had come, upon which the Machigangas strolled along in twos
and threes from their huts, helped us ashore with the baggage, and
prepared the evening meal. Here we sat down with five Italians, who had
ventured into the rubber fields with golden ideas as to profits. After
having lost the larger part of their merchandise, chiefly cinchona, in
the rapids the year before, they had established themselves here with
the idea of picking rubber. Without capital, they followed the ways of
the itinerant rubber picker and had gathered “caucho,” the poorer of the
two kinds of rubber. No capital is required; the picker simply cuts down
the likeliest trees, gathers the coagulated sap, and floats it
down-stream to market. After a year of this life they had grown restless
and were venturing on other schemes for the great down-river rubber
country.

[Illustration: FIG. 13--Composition of tropical vegetation in the rain
forest above Pongo de Mainique, elevation 2,500 feet (760 m.). Scores of
species occur within the limits of a single photograph.]

[Illustration: FIG. 14--The mule trail in the rain forest between
Rosalina and Pongo de Mainique. Each pool is from one and a half to two
feet deep. Even in the dry season these holes are full of water, for the
sunlight penetrates the foliage at a few places only.]

[Illustration: FIG. 15--Topography and vegetation from the Tocate pass,
7,100 feet (2,164 m.), between Rosalina and Pongo de Mainique. See Fig.
53a. This is in the zone of maximum rainfall. The cumulo-nimbus clouds
are typical and change to nimbus in the early afternoon.]

[Illustration: FIG. 16--The Expedition’s thirty-foot canoe at the mouth
of the Timpia below Pongo de Mainique.]

A few weeks later, on returning through the forest, we met their
carriers with a few small bundles, the only part of their cargo they had
saved from the river. Without a canoe or the means to buy one they had
built rafts, which were quickly torn to pieces in the rapids. We, too,
should have said “_pobres Italianos_” if their venture had not been
plainly foolish. The rubber territory is difficult enough for men
with capital; for men without capital it is impossible. Such men either
become affiliated with organized companies or get out of the region when
they can. A few, made desperate by risks and losses, cheat and steal
their way to rubber. Two years before our trip an Italian had murdered
two Frenchmen just below the Pongo and stolen their rubber cargo,
whereupon he was shot by Machigangas under the leadership of Domingo,
the chief who was with us on a journey from Pongo de Mainique to the
mouth of the Timpia. Afterward they brought his skull to the top of a
pass along the forest trail and set it up on a cliff at the very edge of
Machiganga-land as a warning to others of his kind.

At Mulanquiato we secured five Machigangas and a boy interpreter, and on
August 17 made the last and most difficult portion of our journey. We
found these Indians much more skilful than our earlier boatmen.
Well-trained, alert, powerful, and with excellent team-play, they swept
the canoe into this or that thread of the current, and took one after
another of the rapids with the greatest confidence. No sooner had we
passed the Sintulini rapids, fully a mile long, than we reached the
mouth of the Pomareni. This swift tributary comes in almost at right
angles to the main river and gives rise to a confusing mass of standing
waves and conflicting currents rendered still more difficult by the
whirlpool just below the junction. So swift is the circling current of
the maëlstrom that the water is hollowed out like a great bowl, a really
formidable point and one of our most dangerous passages; a little too
far to the right and we should be thrown over against the cliff-face; a
little too far to the left and we should be caught in the whirlpool.
Once in the swift current the canoe became as helpless as a chip. It was
turned this way and that, each turn heading it apparently straight for
destruction. But the Indians had judged their position well, and though
we seemed each moment in a worse predicament, we at last skimmed the
edge of the whirlpool and brought our canoe to shore just beyond its
rim.

A little farther on we came to the narrow gateway of the Pongo, where
the entire volume of the river flows between cliffs at one point no
more than fifty feet apart. Here are concentrated the worst rapids of
the lower Urubamba. For nearly fifteen miles the river is an unbroken
succession of rapids, and once within its walls the Pongo offers small
chance of escape. At some points we were fortunate enough to secure a
foothold along the edge of the river and to let our canoe down by ropes.
At others we were obliged to take chances with the current, though the
great depth of water in most of the Pongo rapids makes them really less
formidable in some respects than the shallow rapids up stream. The chief
danger here lies in the rotary motion of the water at the sharpest
bends. The effect at some places is extraordinary. A floating object is
carried across stream like a feather and driven at express-train speed
against a solid cliff. In trying to avoid one of these cross-currents
our canoe became turned midstream, we were thrown this way and that, and
at last shot through three standing waves that half filled the canoe.

Below the worst rapids the Pongo exhibits a swift succession of natural
wonders. Fern-clad cliffs border it, a bush resembling the juniper
reaches its dainty finger-like stems far out over the river, and the
banks are heavily clad with mosses. The great woods, silent,
impenetrable, mantle the high slopes and stretch up to the limits of
vision. Cascades tumble from the cliff summits or go rippling down the
long inclines of the slate beds set almost on edge. Finally appear the
white pinnacles of limestone that hem in the narrow lower entrance or
outlet of the Pongo. Beyond this passage one suddenly comes out upon the
edge of a rolling forest-clad region, the rubber territory, the country
of the great woods. Here the Andean realm ends and Amazonia begins.

From the summits of the white cliffs 4,000 feet above the river we were
in a few days to have one of the most extensive views in South America.
The break between the Andean Cordillera and the hill-dotted plains of
the lower Urubamba valley is almost as sharp as a shoreline. The rolling
plains are covered with leagues upon leagues of dense, shadowy,
fever-haunted jungle. The great river winds through in a series of
splendid meanders, and with so broad a channel as to make it visible
almost to the horizon. Down river from our lookout one can reach ocean
steamers at Iquitos with less than two weeks of travel. It is three
weeks to the Pacific _via_ Cuzco and more than a month if one takes the
route across the high bleak lava-covered country which we were soon to
cross on our way to the coast at Camaná.

CHAPTER III

THE RUBBER FORESTS

The white limestone cliffs at Pongo de Mainique are a boundary between
two great geographic provinces (Fig. 17). Down valley are the vast river
plains, drained by broad meandering rivers; up valley are the rugged
spurs of the eastern Andes and their encanyoned streams (Fig. 18). There
are outliers of the Andes still farther toward the northeast where hangs
the inevitable haze of the tropical horizon, but the country beyond them
differs in no important respect from that immediately below the Pongo.

[Illustration: FIG. 17--Regional diagram of the Eastern Andes (here the
Cordillera Vilcapampa) and the adjacent tropical plains. For an
explanation of the method of construction and the symbolism of the
diagram see p. 51.]

The foot-path to the summit of the cliffs is too narrow and steep for
even the most agile mules. It is simply impassable for animals without
hands. In places the packs are lowered by ropes over steep ledges and
men must scramble down from one projecting root or swinging vine to
another. In the breathless jungle it is a wearing task to pack in all
supplies for the station below the Pongo and to carry out the season’s
rubber. Recently however the ancient track has been replaced by a road
that was cut with great labor, and by much blasting, across the mountain
barrier, and at last mule transport has taken the place of the Indian.

[Illustration: FIG. 18--Index map for the nine regional diagrams in the
pages following. A represents Fig. 17; B, 42; C, 36; D, 32; E, 34; F,
25; G, 26; and H, 65.]

In the dry season it is a fair and delightful country--that on the
border of the mountains. In the wet season the traveler is either
actually marooned or he must slosh through rivers of mud and water that
deluge the trails and break the hearts of his beasts (Fig. 14). Here and
there a large shallow-rooted tree has come crashing down across the
trail and with its four feet of circumference and ten feet of plank
buttress it is as difficult to move as a house. A new trail must be cut
around it. A little farther on, where the valley wall steepens and one
may look down a thousand feet of slope to the bed of a mountain torrent,
a patch of trail has become soaked with water and the mules pick their
way, trembling, across it. Two days from Yavero one of our mules went
over the trail, and though she was finally recovered she died of her
injuries the following night. After a month’s work in the forest a mule
must run free for two months to recover. The packers count on losing one
beast out of five for every journey into the forest. It is not solely a
matter of work, though this is terrific; it is quite largely a matter of
forage. In spite of its profusion of life (Fig. 13) and its really vast
wealth of species, the tropical forest is all but barren of grass. Sugar
cane is a fair substitute, but there are only a few cultivated spots.
The more tender leaves of the trees, the young shoots of cane in the
_carrizo_ swamps, and the grass-like foliage of the low bamboo are the
chief substitutes for pasture. But they lead to various disorders,
besides requiring considerable labor on the part of the dejected peons
who must gather them after a day’s heavy work with the packs.

Overcoming these enormous difficulties is expensive and some one must
pay the bill. As is usual in a pioneer region, the native laborer pays a
large part of it in unrequited toil; the rest is paid by the rubber
consumer. For this is one of the cases where a direct road connects the
civilized consumer and the barbarous producer. What a story it could
tell if a ball of smoke-cured rubber on a New York dock were endowed
with speech--of the wet jungle path, of enslaved peons, of vile abuses
by immoral agents, of all the toil and sickness that make the tropical
lowland a reproach!

[Illustration: FIG. 19--Moss-draped trees in the rain forest near Abra
Tocate between Rosalina and Pongo de Mainique.]

[Illustration: FIG. 20--Yavero, a rubber station on the Yavero
(Paucartambo) River, a tributary of the Urubamba. Elevation 1,600 feet
(490 m.).]

In the United States the specter of slavery haunted the national
conscience almost from the beginning of national life, and the ghost was
laid only at the cost of one of the bloodiest wars in history. In other
countries, as in sugar-producing Brazil, the freeing of the slaves meant
not a war but the verge of financial ruin besides a fundamental
change in the social order and problems as complex and wearisome as any
that war can bring. Everywhere abolition was secured at frightful cost.

[Illustration: FIG. 21--Clearing in the tropical forest between Rosalina
and Pabellon. This represents the border region where the
forest-dwelling Machiganga Indians and the mountain Indians meet. The
clearings are occupied by Machigangas whose chief crops are yuca and
corn; in the extreme upper left-hand corner are grassy slopes occupied
by Quechua herdsmen and farmers who grow potatoes and corn.]

The spirit that upheld the new founders of the western republics in
driving out slavery was admirable, but as much cannot be said of their
work of reconstruction. We like to pass over those dark days in our own
history. In South America there has lingered from the old slave-holding
days down to the present, a labor system more insidious than slavery,
yet no less revolting in its details, and infinitely more difficult to
stamp out. It is called peonage; it should be called slavery. In
Bolivia, Peru, and Brazil it flourishes now as it ever did in the
fruitful soil of the interior provinces where law and order are bywords
and where the scarcity of workmen will long impel men to enslave labor
when they cannot employ it. Peonage _is_ slavery, though as in all slave
systems there are many forms under which the system is worked out. We
commonly think that the typical slave is one who is made to work hard,
given but little food, and at the slightest provocation is tied to a
post and brutally whipped. This is indeed the fate of many slaves or
“peons” so-called, in the Amazon forests; but it is no more the rule
than it was in the South before the war, for a peon is a valuable piece
of property and if a slave raider travel five hundred miles through
forest and jungle-swamp to capture an Indian you may depend upon it that
he will not beat him to death merely for the fun of it.

That unjust and frightfully cruel floggings are inflicted at times and
in some places is of course a result of the lack of official restraint
that drunken owners far from the arm of the law sometimes enjoy. When a
man obtains a rubber concession from the government he buys a kingdom.
Many of the rubber territories are so remote from the cities that
officials can with great difficulty be secured to stay at the customs
ports. High salaries must be paid, heavy taxes collected, and grafting
of the most flagrant kind winked at. Often the concessionaire himself is
chief magistrate of his kingdom by law. Under such a system, remote from
all civilizing influences, the rubber producer himself oftentimes a
lawless border character or a downright criminal, no system of
government would be adequate, least of all one like peonage that permits
or ignores flagrant wrongs because it is so expensive to enforce
justice.

The peonage system continues by reason of that extraordinary difficulty
in the development of the tropical lowland of South America--the lack of
a labor supply. The population of Amazonia now numbers less than one
person to the square mile. The people are distributed in small groups of
a dozen to twenty each in scattered villages along the river banks or in
concealed clearings reached by trails known only to the Indians. Nearly
all of them still live in the same primitive state in which they lived
at the time of the Discovery. In the Urubamba region a single cotton
shirt is worn by the married men and women, while the girls and boys in
many cases go entirely naked except for a loincloth or a necklace of
nuts or monkeys’ teeth (Fig. 23). A cane hut with a thatch to keep out
the heavy rains is their shelter and their food is the yuca, sugar cane,
Indian corn, bananas of many kinds, and fish. A patch of yuca once
planted will need but the most trifling attention for years. The small
spider monkey is their greatest delicacy and to procure it they will
often abandon every other project and return at their own sweet and
belated will.

[Illustration: FIG. 22--Trading with Machiganga Indians in a reed swamp
at Santao Anato, Urubamba Valley, before Rosalina. Just outside the
picture on the right is a platform on which corn is stored for
protection against rodents and mildew. On the left is the corner of a
grass-thatched cane hut.]

In the midst of this natural life of the forest-dwelling Indian appears
the rubber man, who, to gather rubber, must have rubber “pickers.” If he
lives on the edge of the great Andean Cordillera, laborers may be
secured from some of the lower valleys, but they must be paid well for
even a temporary stay in the hot and unhealthful lowlands. Farther out
in the great forest country the plateau Indians will not go and only the
scattered tribes remain from which to recruit laborers. For the
nature-life of the Indian what has the rubber gatherer to offer? Money?
The Indian uses it for ornament only. When I once tried with money to
pay an Indian for a week’s services he refused it. In exchange for his
severe labor he wanted nothing more than a fish-hook and a ring, the two
costing not more than a penny apiece! When his love for ornament has
once been gratified the Indian ceases to work. His food and shelter
and clothing are of the most primitive kind, but they are the best in
the world for him because they are the only kind he has known. So where
money and finery fail the lash comes in. The rubber man says that the
Indian is lazy and must be made to work; that there is a great deal of
work to be done and the Indian is the only laborer who can be found;
that if rubber and chocolate are produced the Indian must be made to
produce them; and that if he will not produce them for pay he must be
enslaved.

[Illustration: FIG. 23--Ornaments and fabrics of the Machiganga Indians
at Yavero. The nuts are made up into strings, pendants, and heavy
necklaces. To the left of the center is one that contains feathers and
four drumsticks of a bird about the size of a small wild
turkey--probably the so-called turkey inhabiting the eastern mountain
valleys and the adjacent border of the plains, and hunted as an
important source of food. The cord in the upper right-hand corner is
used most commonly for heel supports in climbing trees. The openwork
sack is convenient for carrying game, fish, and fruit; the finely woven
sacks are used for carrying red ochre for ornamenting or daubing faces
and arms. They are also used for carrying corn, trinkets, and game.]

It is a law of the rubber country that when an Indian falls into debt to
a white man he must work for the latter until the debt is discharged. If
he runs away before the debt is canceled or if he refuses to work or
does too little work he may be flogged. Under special conditions such
laws are wise. In the hands of the rubber men they are the basis of
slavery. For, once the rubber interests begin to suffer, the promoters
look around for a chance to capture free Indians. An expedition is
fitted out that spends weeks exploring this river or that in getting on
the track of unattached Indians. When a settlement is found the men are
enslaved and taken long distances from home finally to reach a rubber
property. There they are given a corner of a hut to sleep in, a few
cheap clothes, a rubber-picking outfit, and a name. In return for these
articles the unwilling Indian is charged any fanciful price that comes
into the mind of his “owner,” and he must thereupon work at a per diem
wage also fixed by the owner. Since his obligations increase with time,
the Indian may die over two thousand dollars in debt!

Peonage has left frightful scars upon the country. In some places the
Indians are fugitives, cultivating little farms in secreted places but
visiting them only at night or after carefully reconnoitering the spot.
They change their camps frequently and make their way from place to
place by secret trails, now spending a night or two under the shelter of
a few palm leaves on a sandbar, again concealing themselves in almost
impenetrable jungle. If the hunter sometimes discovers a beaten track he
follows it only to find it ending on a cliff face or on the edge of a
lagoon where concealment is perfect. There are tribes that shoot the
white man at sight and regard him as their bitterest enemy. Experience
has led them to believe that only a dead white is a good white,
reversing our saying about the North American Indian; and that even when
he comes among them on peaceful errands he is likely to leave behind him
a trail of syphilis and other venereal diseases scarcely less deadly
than his bullets.

However, the peonage system is not hideous everywhere and in all its
aspects. There are white owners who realize that in the long run the
friendship of the Indians is an asset far greater than unwilling service
and deadly hatred. Some of them have indeed intermarried with the
Indians and live among them in a state but little above savagery. In the
Mamoré country are a few owners of original princely concessions who
have grown enormously wealthy and yet who continue to live a primitive
life among their scores of illegitimate descendants. The Indians look
upon them as benefactors, as indeed many of them are, defending the
Indians from ill treatment by other whites, giving them clothing and
ornaments, and exacting from them only a moderate amount of labor. In
some cases indeed the whites have gained more than simple gratitude for
their humane treatment of the Indians, some of whom serve their masters
with real devotion.

When the “rubber barons” wish to discourage investigation of their
system they invite the traveler to leave and he is given a canoe and
oarsmen with which to make his way out of the district. Refusal to
accept an offer of canoes and men is a declaration of war. An agent of
one of the London companies accepted such a challenge and was promptly
told that he would not leave the territory alive. The threat would have
held true in the case of a less skilful man. Though Indians slept in the
canoes to prevent their seizure, he slipped past the guards in the
night, swam to the opposite shore, and there secured a canoe within
which he made a difficult journey down river to the nearest post where
food and an outfit could be secured.

A few companies operating on or near the border of the Cordillera have
adopted a normal labor system, dependent chiefly upon people from the
plateau and upon the thoroughly willing assistance of well-paid forest
Indians. The Compañia Gomera de Mainique at Puerto Mainique just below
the Pongo is one of these and its development of the region without
violation of native rights is in the highest degree praiseworthy. In
fact the whole conduct of this company is interesting to a geographer,
as it reflects at every point the physical nature of the country.

The government is eager to secure foreign capital, but in eastern Peru
can offer practically nothing more than virgin wealth, that is, land and
the natural resources of the land. There are no roads, virtually no
trails, no telegraph lines, and in most cases no labor. Since the old
Spanish grants ran at right angles to the river so as to give the owners
a cross-section of varied resources, the up-river plantations do not
extend down into the rubber country. Hence the more heavily forested
lower valleys and plains are the property of the state. A man can buy a
piece of land down there, but from any tract within ordinary means only
a primitive living can be obtained. The pioneers therefore are the
rubber men who produce a precious substance that can stand the enormous
tax on production and transportation. They do not want the land--only
the exclusive right to tap the rubber trees upon it. Thus there has
arisen the concession plan whereby a large tract is obtained under
conditions of money payment or of improvements that will attract
settlers or of a tax on the export.

The “caucho” or poorer rubber of the Urubamba Valley begins at 3,000
feet (915 m.) and the “hevea” or better class is a lower-valley and
plains product. The rubber trees thereabouts produce 60 grams (2 ozs.)
of dry rubber each week for eight months. After yielding rubber for this
length of time a tree is allowed to rest four or five years. “Caucho” is
produced from trees that are cut down and ringed with machetes, but it
is from fifty to sixty cents cheaper owing to the impurities that get
into it. The wood, not the nut, of the _Palma carmona_ is used for
smoking or “curing” the rubber. The government had long been urged to
build a road into the region in place of the miserable track--absolutely
impassable in the wet season--that heretofore constituted the sole
means of exit. About ten years ago Señor Robledo at last built a
government trail from Rosalina to Yavero about 100 miles long. While it
is a wretched trail it is better than the old one, for it is more direct
and it is better drained. In the wet season parts of it are turned into
rivers and lakes, but it is probably the best that could be done with
the small grant of twenty thousand dollars.

With at least an improvement in the trail it became possible for a
rubber company to induce _cargadores_ or packers to transport
merchandise and rubber and to have a fair chance of success. Whereupon a
rubber company was organized which obtained a concession of 28,000
hectares (69,188 acres) of land on condition that the company finish a
road one and one-half meters wide to the Pongo, connecting with the road
which the government had extended to Yavero. The land given in payment
was not continuous but was selected in lots by the company in such a way
as to secure the best rubber trees over an area several times the size
of the concession. The road was finished by William Tell after four
years’ work at a cost of about seventy-five thousand dollars. The last
part of it was blasted out of slate and limestone and in 1912 the first
pack train entered Puerto Mainique.

The first rubber was taken out in November, 1910, and productive
possibilities proved by the collection of 9,000 kilos (19,841 pounds) in
eight months.

If a main road were the chief problem of the rubber company the business
would soon be on a paying basis, but for every mile of road there must
be cut several miles of narrow trail (Fig. 14), as the rubber trees grow
scattered about--a clump of a half dozen here and five hundred feet
farther on another clump and only scattered individuals between.
Furthermore, about twenty-five years ago rubber men from the Ucayali
came up here in launches and canoes and cut down large numbers of trees
within reach of the water courses and by ringing the trunks every few
feet with machetes “bled” them rapidly and thus covered a large
territory in a short time, and made huge sums of money when the price of
rubber was high. Only a few of the small trees that were left are now
mature. These, the mature trees that were overlooked, and the virgin
stands farther from the rivers are the present sources of rubber.

In addition to the trails small cabins must be built to shelter the
hired laborers from the plateau, many of whom bring along their women
folk to cook for them. The combined expense to a company of these
necessary improvements before production can begin is exceedingly heavy.
There is only one alternative for the prospective exploiter: to become a
vagrant rubber gatherer. With tents, guns, machetes, cloth, baubles for
trading, tinned food for emergencies, and with pockets full of English
gold parties have started out to seek fortunes in the rubber forests. If
the friendship of a party of Indians can be secured by adequate gifts
large amounts of rubber can be gathered in a short time, for the Indians
know where the rubber trees grow. On the other hand, many fortunes have
been lost in the rubber country. Some of the tribes have been badly
treated by other adventurers and attack the newcomers from ambush or
gather rubber for a while only to overturn the canoe in a rapid and let
the river relieve them of selfish friends.

The Compañia Gomera de Mainique started out by securing the good-will of
the forest Indians, the Machigangas. They come and go in friendly visits
to the port at Yavero. If one of them is sick he can secure free
medicine from the agent. If he wishes goods on credit he has only to ask
for them, for the agent knows that the Indian’s sense of fairness will
bring him back to work for the company. Without previous notice a group
of Indians appears:

“We owe,” they announce.

“Good,” says the agent, “build me a house.”

They select the trees. Before they cut them down they address them
solemnly. The trees must not hold their destruction against the Indians
and they must not try to resist the sharp machetes. Then the Indians set
to work. They fell a tree, bind it with light ropes woven from the wild
cotton, and haul it to its place. That is all for the day. They play in
the sun, do a little hunting, or look over the agent’s house, touching
everything, talking little, exclaiming much. They dip their wet fingers
in the sugar bowl and taste, turn salt out upon their hands, hold
colored solutions from the medicine chest up to the light, and pull out
and push in the corks of the bottles. At the end of a month or two the
house is done. Then they gather their women and babies together and say:

“Now we go,” without asking if the work corresponds with the cost of the
articles they had bought. Their judgment is good however. Their work is
almost always more valuable than the articles. Then they shake hands all
around.

“We will come again,” they say, and in a moment have disappeared in the
jungle that overhangs the trail.

With such labor the Compañia Gomera de Mainique can do something, but it
is not much. The regular seasonal tasks of road-building and
rubber-picking must be done by imported labor. This is secured chiefly
at Abancay, where live groups of plateau Indians that have become
accustomed to the warm climate of the Abancay basin. They are employed
for eight or ten months at an average rate of fifty cents gold per day,
and receive in addition only the simplest articles of food.

At the end of the season the gang leaders are paid a _gratificación_, or
bonus, the size of which depends upon the amount of rubber collected,
and this in turn depends upon the size of the gang and the degree of
willingness to work. In the books of the company I saw a record of
_gratificaciónes_ running as high as $600 in gold for a season’s work.

Some of the laborers become sick and are cared for by the agent until
they recover or can be sent back to their homes. Most of them have fever
before they return.

The rubber costs the company two _soles_ ($1.00) produced at Yavero. The
two weeks’ transportation to Cuzco costs three and a half soles ($1.75)
per twenty-five pounds. The exported rubber, known to the trade as
Mollendo rubber, in contrast to the finer “Pará” rubber from the lower
Amazon, is shipped to Hamburg. The cost for transportation from port to
port is $24.00 per English ton (1,016 kilos). There is a Peruvian tax of
8 per cent of the net value in Europe, and a territorial tax of two
soles ($1.00) per hundred pounds. All supplies except the few vegetables
grown on the spot cost tremendously. Even dynamite, hoes, clothing,
rice--to mention only a few necessities--must pay the heavy cost of
transportation after imposts, railroad and ocean freight, storage and
agents’ percentages are added. The effect of a disturbed market is
extreme. When, in 1911, the price of rubber fell to $1.50 a kilo at
Hamburg the company ceased exporting. When it dropped still lower in
1912 production also stopped, and it is still doubtful, in view of the
growing competition of the East-Indian plantations with their cheap
labor, whether operations will ever be resumed. Within three years no
less than a dozen large companies in eastern Peru and Bolivia have
ceased operations. In one concession on the Madre de Dios the withdrawal
of the agents and laborers from the posts turned at last into flight, as
the forest Indians, on learning the company’s policy, rapidly ascended
the river in force, committing numerous depredations. The great war has
also added to the difficulties of production.

Facts like these are vital in the consideration of the future of the
Amazon basin and especially its habitability. It was the dream of
Humboldt that great cities should arise in the midst of the tropical
forests of the Amazon and that the whole lowland plain of that river
basin should become the home of happy millions. Humboldt’s vision may
have been correct, though a hundred years have brought us but little
nearer its realization. Now, as in the past four centuries, man finds
his hands too feeble to control the great elemental forces which have
shaped history. The most he can hope for in the next hundred years at
least is the ability to dodge Nature a little more successfully, and
here and there by studies in tropical hygiene and medicine, by the
substitution of water-power for human energy, to carry a few of the
outposts and prepare the way for a final assault in the war against the
hard conditions of climate and relief. We hear of the Madeira-Mamoré
railroad, 200 miles long, in the heart of a tropical forest and of the
commercial revolution it will bring. Do we realize that the forest which
overhangs the rails is as big as the whole plain between the Rockies
and the Appalachians, and that the proposed line would extend only as
far as from St. Louis to Kansas City, or from Galveston to New Orleans?

Even if twenty whites were eager to go where now there is but one
reluctant pioneer, we should still have but a halting development on
account of the scarcity of labor. When, three hundred years ago, the
Isthmus of Panama stood in his way, Gomara wrote to his king: “There are
mountains, but there are also hands,” as if men could be conjured up
from the tropical jungle. From that day to this the scarcity of labor
has been the chief difficulty in the lowland regions of tropical South
America. Even when medicine shall have been advanced to the point where
residence in the tropics can be made safe, the Amazon basin will lack an
adequate supply of workmen. Where Humboldt saw thriving cities, the
population is still less than one to the square mile in an area as large
as fifteen of our Mississippi Valley states. We hear much about a rich
soil and little about intolerable insects; the climate favors a good
growth of vegetation, but a man can starve in a tropical forest as
easily as in a desert; certain tributaries of the Negro are bordered by
rich rubber forests, yet not a single Indian hut may be found along
their banks. Will men of the white race dig up the rank vegetation,
sleep in grass hammocks, live in the hot and humid air, or will they
stay in the cooler regions of the north and south? Will they rear
children in the temperate zones, or bury them in the tropics?

What Gorgas did for Panama was done for intelligent people. Can it be
duplicated in the case of ignorant and stupid laborers? Shall the white
man with wits fight it out with Nature in a tropical forest, or fight it
out with his equals under better skies?

The tropics must be won by strong hands of the lowlier classes who are
ignorant or careless of hygiene, and not by the khaki-clad robust young
men like those who work at Panama. Tropical medicine can do something
for these folk, but it cannot do much. And we cannot surround every
laborer’s cottage with expensive screens, oiled ditches, and well-kept
lawns. There is a practical optimism and a sentimental optimism. The one
is based on facts; the other on assumptions. It is pleasant to think
that the tropical forest may be conquered. It is nonsense to say that we
are now conquering it in any comprehensive and permanent way. That sort
of conquest is still a dream, as when Humboldt wrote over a hundred
years ago.

CHAPTER IV

THE FOREST INDIANS

The people of a tropical forest live under conditions not unlike those
of the desert. The Sahara contains 2,000,000 persons within its borders,
a density of one-half to the square mile. This is almost precisely the
density of population of a tract of equivalent size in the lowland
forests of South America. Like the oases groups in the desert of aridity
are the scattered groups along the river margins of the forest. The
desert trails run from spring to spring or along a valley floor where
there is seepage or an intermittent stream; the rivers are the highways
of the forest, the flowing roads, and away from them one is lost in as
true a sense as one may be lost in the desert.

A man may easily starve in the tropical forest. Before starting on even
a short journey of two or three days a forest Indian stocks his canoe
with sugar cane and yuca and a little parched corn. He knows the
settlements as well as his desert brother knows the springs. The Pahute
Indian of Utah lives in the irrigated valleys and makes annual
excursions across the desert to the distant mountains to gather the
seeds of the nut pine. The Machiganga lives in the hills above the
Urubamba and annually comes down through the forest to the river to fish
during the dry season.

The Machigangas are one of the important tribes of the Amazon basin.
Though they are dispersed to some extent upon the plains their chief
groups are scattered through the heads of a large number of valleys near
the eastern border of the Andes. Chief among the valleys they occupy are
the Pilcopata, Tono, Piñi-piñi, Yavero, Yuyato, Shirineiri, Ticumpinea,
Timpia, and Camisea (Fig. 203). In their distribution, in their
relations with each other, in their manner of life, and to some extent
in their personal traits, they display characteristics strikingly like
those seen in desert peoples. Though the forest that surrounds them
suggests plenty and the rivers the possibility of free movement with
easy intercourse, the struggle of life, as in the desert, is against
useless things. Travel in the desert is a conflict with heat and
aridity; but travel in the tropic forest is a struggle against space,
heat, and a superabundant and all but useless vegetation.

The Machigangas are one of the subtribes of the Campas Indians, one of
the most numerous groups in the Amazon Valley. It is estimated that
there are in all about 14,000 to 16,000 of them. Each subtribe numbers
from one to four thousand, and the territory they occupy extends from
the limits of the last plantations--for example, Rosalina in the
Urubamba Valley--downstream beyond the edge of the plains. Among them
three subtribes are still hostile to the whites: the Cashibos, the
Chonta Campas, and the Campas Bravos.

In certain cases the Cashibos are said to be anthropophagous, in the
belief that they will assume the strength and intellect of those they
eat. This group is also continuously at war with its neighbors, goes
naked, uses stone hatchets, as in ages past, because of its isolation
and unfriendliness, and defends the entrances to the tribal huts with
dart and traps. The Cashibos are diminishing in numbers and are now
scattered through the valley of the Gran Pajonal, the left bank of the
Pachitea, and the Pampa del Sacramento.[2]

The friendliest tribes live in the higher valley heads, where they have
constant communication with the whites. The use of the bow and arrow has
not, however, been discontinued among them, in spite of the wide
introduction of the old-fashioned muzzle-loading shotgun, which they
prize much more highly than the latest rifle or breech-loading shotgun
because of its simplicity and cheapness. Accidents are frequent among
them owing to the careless use of fire-arms. On our last day’s journey
on the Urubamba above the mouth of the Timpia one of our Indian boys
dropped his canoe pole on the hammer of a loaded shotgun, and not only
shot his own fingers to pieces, but gravely wounded his father (Fig. 2).
In spite of his suffering the old chief directed our work at the canoe
and even was able to tell us the location of the most favorable channel.
Though the night that followed was as black as ink, with even the stars
obscured by a rising storm, his directions never failed. We poled our
way up five long rapids without special difficulties, now working into
the lee of a rock whose location he knew within a few yards, now
paddling furiously across the channel to catch the upstream current of
an eddy.

The principal groups of Machigangas live in the middle Urubamba and its
tributaries, the Yavero, Yuyato, Shirineiri, Ticumpinea, Timpia,
Pachitea, and others. There is a marked difference in the use of the
land and the mode of life among the different groups of this subtribe.
Those who live in the lower plains and river “playas,” as the patches of
flood plain are called, have a single permanent dwelling and alternately
fish and hunt. Those that live on hill farms have temporary reed huts on
the nearest sandbars and spend the best months of the dry season--April
to October--in fishing and drying fish to be carried to their mountain
homes (Fig. 21). Some families even duplicate _chacras_ or farms at the
river bank and grow yuca and sugar cane. In latter years smallpox,
malaria, and the rubber hunters have destroyed many of the river
villages and driven the Indians to permanent residence in the hills or,
where raids occur, along secret trails to hidden camps.

Their system of agriculture is strikingly adapted to some important
features of tropical soil. The thin hillside soils of the region are but
poorly stocked with humus, even in their virgin condition. Fallen trees
and foliage decay so quickly that the layer of forest mold is
exceedingly thin and the little that is incorporated in the soil is
confined to a shallow surface layer. To meet these special conditions
the Indian makes new clearings by girdling and burning the trees. When
the soil becomes worn out and the crops diminish, the old clearing is
abandoned and allowed to revert to natural growth and a new farm is
planted to corn and yuca. The population is so scattered and thin that
the land assignment system current among the plateau Indians is not
practised among the Machigangas. Several families commonly live together
and may be separated from their nearest neighbors by many miles of
forested mountains. The land is free for all, and, though some heavy
labor is necessary to clear it, once a small patch is cleared it is easy
to extend the tract by limited annual cuttings. Local tracts of
naturally unforested land are rarely planted, chiefly because the
absence of shade has allowed the sun to burn out the limited humus
supply and to prevent more from accumulating. The best soil of the
mountain slopes is found where there is the heaviest growth of timber,
the deepest shade, the most humus, and good natural drainage. It is the
same on the playas along the river; the recent additions to the flood
plain are easy to cultivate, but they lack humus and a fine matrix which
retains moisture and prevents drought or at least physiologic dryness.
Here, too, the timbered areas or the cane swamps are always selected for
planting.

The traditions of the Machigangas go back to the time of the Inca
conquest, when the forest Indians, the “Antis,” were subjugated and
compelled to pay tribute.[3] When the Inca family itself fled from Cuzco
after the Spanish Conquest and sought refuge in the wilderness it was to
the Machiganga country that they came by way of the Vilcabamba and
Pampaconas Valleys. Afterward came the Spaniards and though they did not
exercise governmental authority over the forest Indians they had close
relations with them. Land grants were made to white pioneers for special
services or through sale and with the land often went the right to
exploit the people on it. Some of the concessions were owned by people
who for generations knew nothing save by hearsay of the Indians who
dwelt in the great forests of the valleys. In later years they have been
exploring their lands and establishing so-called relations whereby the
savage “buys” a dollar’s worth of powder or knives for whatever number
of dollars’ worth of rubber the owner may care to extract from him.

The forest Indian is still master of his lands throughout most of the
Machiganga country. He is cruelly enslaved at the rubber posts, held by
the loose bonds of a desultory trade at others, and in a few places, as
at Pongo do Mainique, gives service for both love and profit, but in
many places it is impossible to establish control or influence. The
lowland Indian never falls into the abject condition of his Quechua
brother on the plateau. He is self-reliant, proud, and independent. He
neither cringes before a white nor looks up to him as a superior being.
I was greatly impressed by the bearing of the first of the forest tribes
I met in August, 1911, at Santo Anato. I had built a brisk fire and was
enjoying its comfort when La Sama returned with some Indians whom he had
secured to clear his playa. The tallest of the lot, wearing a colored
band of deer skin around his thick hair and a gaudy bunch of yellow
feathers down his back, came up, looked me squarely in the eye, and
asked

“Tatiry payta?” (What is your name?)

When I replied he quietly sat down by the fire, helping himself to the
roasted corn I had prepared in the hot ashes. A few days later when we
came to the head of a rapid I was busy sketching-in my topographic map
and did not hear his twice repeated request to leave the boat while the
party reconnoitered the rapid. Watching his opportunity he came
alongside from the rear--he was steersman--and, turning just as he was
leaving the boat, gave me a whack in the forehead with his open palm. La
Sama saw the motion and protested. The surly answer was:

“I twice asked him to get out and he didn’t move. What does he think we
run the canoe to the bank for?”

To him the making of a map was inexplicable; I was merely a stupid white
person who didn’t know enough to get out of a canoe when told!

The plateau Indian has been kicked about so long that all his
independence has been destroyed. His goods have been stolen, his
services demanded without recompense, in many places he has no right to
land, and his few real rights are abused beyond belief. The difference
between him and the forest Indian is due quite largely to differences of
environment. The plateau Indian is agricultural, the forest Indian
nomadic and in a hunting stage of development; the unforested plateau
offers no means for concealment of person or property, the forest offers
hidden and difficult paths, easy means for concealment, for ambush, and
for wide dispersal of an afflicted tribe. The brutal white of the
plateau follows altogether different methods when he finds himself in
the Indian country, far from military assistance, surrounded by fearless
savages. He may cheat but he does not steal, and his brutality is always
carefully suited to both time and place.

The Machigangas are now confined to the forest, but the limits of their
territory were once farther upstream, where they were in frequent
conflict with the plateau Indians. As late as 1835, according to General
Miller,[4] they occupied the land as far upstream as the “Encuentro”
(junction) of the Urubamba and the Yanatili (Fig. 53). Miller likewise
notes that the Chuntaguirus, “a superior race of Indians” who lived
“toward the Marañon,” came up the river “200 leagues” to barter with the
people thereabouts.

“They bring parrots and other birds, monkeys, cotton robes white and
painted, wax balsams, feet of the gran bestia, feather ornaments for the
head, and tiger and other skins, which they exchange for hatchets,
knives, scissors, needles, buttons, and any sort of glittering bauble.”

On their yearly excursions they traveled in a band numbering from 200 to
300, since at the mouth of the Paucartambo (Yavero) they were generally
set upon by the Pucapacures. The journey upstream required three months;
with the current they returned home in fifteen days.

Their place of meeting at the mouth of the Yanatili was a response to a
long strip of grassland that extends down the deep and dry Urubamba
Valley, as shown in Figs. 53-B and 55. The wet forests, in which the
Machigangas live, cover the hills back of the valley plantations; the
belt of dry grassland terminates far within the general limits of the
red man’s domain and only 2,000 feet above the sea. It is in this strip
of low grassland that on the one hand the highland and valley dwellers,
and on the other the Indians of the hot forested valleys and the
adjacent lowland found a convenient place for barter. The same
physiographic features are repeated in adjacent valleys of large size
that drain the eastern aspect of the Peruvian Andes, and in each case
they have given rise to the periodic excursions of the trader.

These annual journeys are no longer made. The planters have crept down
valley. The two best playas below Rosalina are now being cleared. Only a
little space remains between the lowest valley plantations and the
highest rubber stations. Furthermore, the Indians have been enslaved by
the rubber men from the Ucayali. The Machigangas, many of whom are
runaway peons, will no longer take cargoes down valley for fear of
recapture. They have the cautious spirit of fugitives except in their
remote valleys. There they are secure and now and then reassert their
old spirit when a lawless trader tries to browbeat them into an
unprofitable trade. Also, they are yielding to the alluring call of the
planter. At Santo Anato they are clearing a playa in exchange for
ammunition, machetes, brandy, and baubles. They no longer make annual
excursions to get these things. They have only to call at the nearest
plantation. There is always a wolf before the door of the planter--the
lack of labor. Yet, as on every frontier, he turns wolf himself when the
lambs come, and without shame takes a week’s work for a penny mirror,
or, worse still, supplies them with firewater, for that will surely
bring them back to him. Since this is expensive they return to their
tribal haunts with nothing except a debauched spirit and an appetite
from which they cannot run away as they did from their task masters in
the rubber forest. Hence the vicious circle: more brandy, more labor;
more labor, more cleared land; more cleared land, more brandy; more
brandy, less Indian. But by that time the planter has a large sugar
estate. Then he can begin to buy the more expensive plateau labor, and
in turn debauch it.

Nature as well as man works against the scattered tribes of Machigangas
and their forest kinsmen. Their country is exceedingly broken by
ramifying mountain spurs and valleys overhung with cliffs or bordered by
bold, wet, fern-clad slopes. It is useless to try to cut your way by a
direct route from one point to another. The country is mantled with
heavy forest. You must follow the valleys, the ancient trails of the
people. The larger valleys offer smooth sand-bars along the border of
which canoes may be towed upstream, and there are little cultivated
places for camps. But only a few of the tribes live along them, for they
are also more accessible to the rubbermen. The smaller valleys,
difficult of access, are more secure and there the tribal remnants live
today. While the broken country thus offers a refuge to fugitive bands
it is the broken country and its forest cover that combine to break up
the population into small groups and keep them in an isolated and
quarrelsome state. Chronic quarreling is not only the product of mere
lack of contact. It is due to many causes, among which is a union of the
habit of migration and divergent tribal speech. Every tribe has its own
peculiar words in addition to those common to the group of tribes to
which it belongs. Moreover each group of a tribe has its distinctive
words. I have seen and used carefully prepared vocabularies--no two of
which are alike throughout. They serve for communication with only a
limited number of families. These peculiarities increase as experiences
vary and new situations call for additions to or changes in their
vocabularies, and when migrating tribes meet their speech may be so
unlike as to make communication difficult. Thus arise suspicion,
misunderstanding, plunder, and chronic war. Had they been a united
people their defense of their rough country might have been successful.
The tribes have been divided and now and again, to get firearms and
ammunition with which to raid a neighbor, a tribe has joined its
fortunes to those of vagrant rubber pickers only to find in time that
its women were debased, its members decimated by strange and deadly
diseases, and its old morality undermined by an insatiable desire for
strong drink.[5] The Indian loses whether with the white or against him.

The forest Indian is held by his environment no less strongly than the
plateau Indian. We hear much about the restriction of the plateau
dweller to the cool zone in which the llama may live. As a matter of
fact he lives far below the cool zone, where he no longer depends upon
the llama but rather upon the mule for transport. The limits of his
range correspond to the limits of the grasslands in the dry valley
pockets already described (p. 42), or on the drier mountain slopes below
the zone of heaviest rainfall (Fig. 54). It is this distribution that
brought him into such intimate contact with the forest Indian. The old
and dilapidated coca terraces of the Quechuas above the Yanatili almost
overlook the forest patches where the Machigangas for centuries built
their rude huts. A good deal has been written about the attempts of the
Incas to extend their rule into this forest zone and about the failure
of these attempts on account of the tropical climate. But the forest
Indian was held by bonds equally secure. The cold climate of the plateau
repelled him as it does today. His haunts are the hot valleys where he
need wear only a wild-cotton shirt or where he may go naked altogether.
That he raided the lands of the plateau Indian is certain, but he could
never displace him. Only along the common borders of their domains,
where the climates of two zones merged into each other, could the forest
Indian and the plateau Indian seriously dispute each other’s claims to
the land. Here was endless conflict but only feeble trade and only the
most minute exchanges of cultural elements.

Even had they been as brothers they would have had little incentive to
borrow cultural elements from each other. The forest dweller requires
bow and arrow; the plateau dweller requires a hoe. There are fish in the
warm river shallows of the forested zone; llamas, vicuña, vizcachas,
etc., are a partial source of food supply on the plateau. Coca and
potatoes are the chief products of the grassy mountain slopes; yuca,
corn, bananas, are the chief vegetable foods grown on the tiny
cultivated patches in the forest. The plateau dweller builds a
thick-walled hut; the valley dweller a cane shack. So unlike are the two
environments that it would be strange if there had been a mixture of
racial types and cultures. The slight exchanges that were made seem
little more than accidental. Even today the Machigangas who live on the
highest slopes own a few pigs obtained from Quechuas, but they never eat
their flesh; they keep them for pets merely. I saw not a single woolen
article among the Indians along the Urubamba whereas Quechuas with
woolen clothing were going back and forth regularly. Their baubles were
of foreign make; likewise their few hoes, likewise their guns.

They clear the forest about a mid-cotton tree and spin and weave the
cotton fiber into sacks, cords for climbing trees when they wish to
chase a monkey, ropes for hauling their canoes, shirts for the married
men and women, colored head-bands, and fish nets. The slender strong
bamboo is gathered for arrows. The chunta palm, like bone for hardness,
supplies them with bows and arrow heads. The brilliant red and yellow
feathers of forest birds, also monkey bones and teeth, are their natural
ornaments. Their life is absolutely distinct from that of their Quechua
neighbors. Little wonder that for centuries forest and plateau Indians
have been enemies and that their cultures are so distinct, for their
environment everywhere calls for unlike modes of existence and distinct
cultural development.

CHAPTER V

THE COUNTRY OF THE SHEPHERDS

The lofty mountain zones of Peru, the high bordering valleys, and the
belts of rolling plateau between are occupied by tribes of shepherds. In
that cold, inhospitable region at the top of the country are the highest
permanent habitations in the world--17,100 feet (5,210 m.)--the loftiest
pastures, the greatest degree of adaptation to combined altitude and
frost. It is here only a step from Greenland to Arcady. Nevertheless it
is Greenland that has the people. Why do they shun Arcady? To the
traveler from the highlands the fertile valleys between 5,000 and 8,000
feet (1,500 to 2,500 m.) seem like the abode of friendly spirits to
whose charm the highland dweller must yield. Every pack-train from
valley to highland carries luxury in the form of fruit, coca, cacao, and
sugar. One would think that every importation of valley products would
be followed by a wave of migration from highland to valley. On the
contrary the highland people have clung to their lofty pastures for
unnumbered centuries. Until the Conquest the last outposts of the Incas
toward the east were the grassy ridges that terminate a few thousand
feet below the timber line.

In this natural grouping of the people where does choice or blind
prejudice or instinct leave off? Where does necessity begin? There are
answers to most of these questions to be found in the broad field of
geographic comparison. But before we begin comparisons we must study the
individual facts upon which they rest. These facts are of almost every
conceivable variety. They range in importance from a humble shepherd’s
stone corral on a mountain slope to a thickly settled mountain basin.
Their interpretation is to be sought now in the soil of rich playa
lands, now in the fixed climatic zones and rugged relief of deeply
dissected, lofty highlands in the tropics. Some of the controlling
factors are historical, others economic; still other factors have
exerted their influence through obscure psychologic channels almost
impossible to trace. The _why_ of man’s distribution over the earth is
one of the most complicated problems in natural science, and the
solution of it is the chief problem of the modern geographer.

At first sight the mountain people of the Peruvian Andes seem to be
uniform in character and in mode of life. The traveler’s first
impression is that the same stone-walled, straw-thatched type of hut is
to be found everywhere, the same semi-nomadic life, the same degrees of
poverty and filth. Yet after a little study the diversity of their lives
is seen to be, if not a dominating fact, at least one of surprising
importance. Side by side with this diversity there runs a corresponding
diversity of relations to their physical environment. Nowhere else on
the earth are greater physical contrasts compressed within such small
spaces. If, therefore, we accept the fundamental theory of geography
that there is a general, necessary, varied, and complex relation between
man and the earth, that theory ought here to find a really vast number
of illustrations. A glance at the accompanying figures discloses the
wide range of relief in the Peruvian Andes. The corresponding range in
climate and in life therefore furnishes an ample field for the
application of the laws of human distribution.

In analyzing the facts of distribution we shall do well to begin with
the causes and effects of migration. Primitive man is in no small degree
a wanderer. His small resources often require him to explore large
tracts. As population increases the food quest becomes more intense, and
thus there come about repeated emigrations which increase the food
supply, extend its variety, and draw the pioneers at last into contact
with neighboring groups. The farther back we go in the history of the
race the clearer it becomes that migrations lie at the root of much of
human development. The raid for plunder, women, food, beasts, is a
persistent feature of the life of those primitive men who live on the
border of unlike regions.

The shepherd of the highland and the forest hunter of the plains
perforce range over vast tracts, and each brings back to the home group
news that confirms the tribal choice of habitation or sets it in motion
toward a more desirable place. Superstitions may lead to flight akin to
migration. Epidemics may be interpreted as the work of a malignant
spirit from which men must flee. War may drive a defeated group into the
fastnesses of a mountain forest where pursuit by stream or trail weakens
the pursuer and confines his action, thereby limiting his power. Floods
may come and destroy the cultivated spots. Want or mere desire in a
hundred forms may lead to movement.

Even among forest tribes long stationary the facile canoe and the light
household necessities may easily enable trivial causes to develop the
spirit of restlessness. Pressure of population is a powerful but not a
general cause of movement. It may affect the settled groups of the
desert oases, or the dense population of fertile plains that is rooted
in the soil. On the other hand mere whims may start a nomadic group
toward a new goal. Often the goal is elusive and the tribe turns back to
the old haunts or perishes in the shock of unexpected conflict.

In the case of both primitive societies and those of a higher order the
causes and the results of migration are often contradictory. These will
depend on the state of civilization and the extremes of circumstance.
When the desert blooms the farmer of the Piura Valley in northwestern
Peru turns shepherd and drives his flocks of sheep and goats out into
the short-lived pastures of the great pampa on the west. In dry years he
sends them eastward into the mountains. The forest Indian of the lower
Urubamba is a fisherman while the river is low and lives in a reed hut
beside his cultivated patch of cane and yuca. When the floods come he is
driven to the higher ground in the hills where he has another cultivated
patch of land and a rude shelter. To be sure, these are seasonal
migrations, yet through them the country becomes better known to each
new generation of men. And each generation supplies its pioneers, who
drift into the remoter places where population is scarce or altogether
wanting.

[Illustration: FIG. 24--This stone hut, grass-thatched, is the highest
permanent habitation in Peru, and is believed to be the highest in the
world. Altitude of 17,100 feet (5,210 m.) determined by instrumental
survey. The general geographic relationships of the region in which the
hut is situated are shown in Fig. 25. For location see the topographic
map, Fig. 204.]

Dry years and extremely dry years may have opposite effects. When
moderate dryness prevails the results may be endurable. The oases
become crowded with men and beasts just when they can ill afford to
support them. The alfalfa meadows become overstocked and cattle become
lean and almost worthless. But there is at least bare subsistence. By
contrast, if extreme and prolonged drought prevails, some of the people
are driven forth to more favored spots. At Vallenar in central Chile
some of the workmen in extreme years go up to the nitrate pampa; in wet
years they return. When the agents of the nitrate companies hear of hard
times in a desert valley they offer employment to the stricken people.
It not infrequently happens that when there are droughts in desert Chile
there are abundant rains in Argentina on the other side of the
Cordillera. There has therefore been for many generations an irregular
and slight, though definite, shifting of population from one side of the
mountains to the other as periods of drought and periods of rain
alternated in the two regions. Some think there is satisfactory evidence
to prove that a number of the great Mongolian emigrations took place in
wet years when pasture was abundant and when the pastoral nomad found it
easy to travel. On the other hand it has been urged that the cause of
many emigrations was prolonged periods of drought when the choice lay
between starvation and flight. It is evident from the foregoing that
both views may be correct in spite of the fact that identical effects
are attributed to opposite causes.

[Illustration: FIG. 25--Regional diagram for the Maritime Cordillera to
show the physical relations in the district where the highest habitation
in the world are located. For location, see Fig. 20. It should be
remembered that the orientation of these diagrams is generalized. By
reference to Fig. 20 it will be seen that some portions of the crest of
the Maritime Cordillera run east and west and others north and south.
The same is true of the Cordillera Vilcapampa, Fig. 36.]

_Note on regional diagrams._--For the sake of clearness I have
classified the accompanying facts of human distribution in the
country of the shepherds and represented them graphically in
“regional” diagrams, Figs. 17, 25, 26, 32, 34, 36, 42, 65. These
diagrams are constructed on the principle of dominant control. Each
brings out the factors of greatest importance in the distribution
of the people in a given region. Furthermore, the facts are
compressed within the limits of a small rectangle. This
compression, though great, respects all essential relations. For
example, every location on these diagrams has a concrete
illustration but the accidental relations of the field have been
omitted; the essential relations are preserved. Each diagram is,
therefore, a kind of generalized type map. It bears somewhat the
same relation to the facts of human geography that a block diagram
does to physiography. The darkest shading represents steep
snow-covered country; the next lower grade represents rough but
snow-free country; the lightest shading represents moderate relief;
unshaded parts represent plain or plateau. Small circles represent
forest or woodland; small open-spaced dots, grassland. Fine
alluvium is represented by small closely spaced dots; coarse
alluvium by large closely spaced dots.

To take an illustration. In Figure 32 we have the Apurimac region
near Pasaje (see location map, Fig. 20). At the lower edge of the
rectangle is a snow-capped outlier of the Cordillera Vilcapampa.
The belt of rugged country represents the lofty, steep, exposed,
and largely inaccessible ridges at the mid-elevations of the
mountains below the glaciated slopes at the heads of tributary
valleys. The villages in the belt of pasture might well be
Incahuasi and Corralpata. The floors of the large canyons on either
hand are bordered by extensive alluvial fans. The river courses are
sketched in a diagrammatic way only, but a map would not be
different in its general disposition. Each location is justified by
a real place with the same essential features and relations. In
making the change there has been no alteration of the general
relation of the alluvial lands to each other or to the highland. By
suppressing unnecessary details there is produced a diagram whose
essentials have simple and clear relations. When such a regional
diagram is amplified by photographs of real conditions it becomes a
sort of generalized picture of a large group of geographic facts.
One could very well extend the method to the whole of South
America. It would be a real service to geography to draw up a set
of, say, twelve to fifteen regional diagrams, still further
generalized, for the whole of the continent. As a broad
classification they would serve both the specialist and the general
student. As the basis for a regional map of South America they
would be invaluable if worked out in sufficient detail and
constructed on the indispensable basis of field studies.

It is still an open question whether security or insecurity is more
favorable for the broad distribution of the Peruvian Indians of the
mountain zone which forms the subject of this chapter. Certainly both
tend to make the remoter places better known. Tradition has it that, in
the days of intertribal conflict before the Conquest, fugitives fled
into the high mountain pastures and lived in hidden places and in caves.
Life was insecure and relief was sought in flight. On the other hand
peace has brought security to life. The trails are now safe. A shepherd
may drive his flock anywhere. He no longer has any one to fear in his
search for new pastures. It would perhaps be safe to conclude that there
is equally broad distribution of men in the mountain pastures in time of
peace and in time of war. There is, however, a difference in the kind
of distribution. In time of peace the individual is safe anywhere; in
time of unrest he is safe only when isolated and virtually concealed. By
contrast, the group living near the trails is scattered by plundering
bands and war parties. The remote and isolated group may successfully
oppose the smaller band and the individuals that might reach the remoter
regions. The fugitive group would have nothing to fear from large bands,
for the limited food supply would inevitably cause these to disintegrate
upon leaving the main routes of travel. Probably the fullest exploration
of the mountain pastures has resulted from the alternation of peace and
war. The opposite conditions which these establish foster both kinds of
distribution; hence both the remote group life encouraged by war and the
individual’s lack of restraint in time of peace are probably in large
part responsible for the present widespread occupation of the Peruvian
mountains.

The loftiest habitation in the world (Fig. 24) is in Peru. Between
Antabamba and Cotahuasi occur the highest passes in the Maritime
Cordillera. We crossed at 17,400 feet (5,300 m.), and three hundred feet
lower is the last outpost of the Indian shepherds. The snowline, very
steeply canted away from the sun, is between 17,200 and 17,600 feet
(5,240 to 5,360 m.). At frequent intervals during the three months of
winter, snowfalls during the night and terrific hailstorms in the late
afternoon drive both shepherds and flocks to the shelter of leeward
slopes or steep canyon walls. At our six camps, between 16,000 and
17,200 feet (4,876 and 5,240 m.), in September, 1911, the minimum
temperature ranged from 4° to 20°F. The thatched stone hut that we
passed at 17,100 feet and that enjoys the distinction of being the
highest in the world was in other respects the same as the thousands of
others in the same region. It sheltered a family of five. As we passed,
three rosy-cheeked children almost as fat as the sheep about them were
sitting on the ground in a corner of the corral playing with balls of
wool. Hundreds of alpacas and sheep grazed on the hill slopes and valley
floor, and their tracks showed plainly that they were frequently driven
up to the snowline in those valleys where a trickle of water supported a
band of pasture. Less than a hundred feet below them were other huts and
flocks.

Here we have the limits of altitude and the limits of resources. The
intervalley spaces do not support grass. Some of them are quite bare,
others are covered with mosses. It is too high for even the tola
bush--that pioneer of Alpine vegetation in the Andes. The distance[6] to
Cotahuasi is 75 miles (120 km.), to Antabamba 50 miles (80 km.). Thence
wool must be shipped by pack-train to the railroad in the one case 250
miles (400 km.) to Arequipa, in the other case 200 miles (320 km.) to
Cuzco. Even the potatoes and barley, which must be imported, come from
valleys several days’ journey away. The question naturally arises why
these people live on the rim of the world. Did they seek out these
neglected pastures, or were they driven to them? Do they live here by
choice or of necessity? The answer to these questions introduces two
other geographic factors of prime importance, the one physical, the
other economic.

The main tracts of lofty pasture above Antabamba cover mountain slopes
and valley floor alike, but the moist valley floors supply the best
grazing. Moreover, the main valleys have been intensively glaciated.
Hence, though their sides are steep walls, their floors are broad and
flat. Marshy tracts, periodically flooded, are scattered throughout, and
here and there are overdeepened portions where lakes have gathered.
There is a thick carpet of grass, also numerous huts and corrals, and
many flocks. At the upper edge of the main zone of pasture the grasses
become thin and with increasing altitude give out altogether except
along the moist valley floors or on shoulders where there is seepage.

If the streams head in dry mountain slopes without snow the grassy bands
of the valley floor terminate at moderate elevations. If the streams
have their sources in snowfields or glaciers there is a more uniform
run-off, and a ribbon of pasture may extend to the snowline. To the
latter class belong the pastures that support these remote people.

In the case of the Maritime Andes the great elevation of the snowline is
also a factor. If, in Figure 25, we think of the snowline as at the
upper level of the main zone of pasture then we should have the
conditions shown in Figure 36, where the limit of general, not local,
occupation is the snowline, as in the Cordillera Vilcapampa and between
Chuquibambilla and Antabamba.

A third factor is the character of the soil. Large amounts of volcanic
ash and lapilli were thrown out in the late stages of volcanic eruption
in which the present cones of the Maritime Andes were formed. The coarse
texture of these deposits allows the ready escape of rainwater. The
combination of extreme aridity and great elevation results in a double
restraint upon vegetation. Outside of the moist valley floors, with
their film of ground moraine on whose surface plants find a more
congenial soil, there is an extremely small amount of pasture. Here are
the natural grazing grounds of the fleet vicuña. They occur in
hundreds, and so remote and little disturbed are they that near the main
pass one may count them by the score. As we rode by, many of them only
stared at us without taking the trouble to get beyond rifle shot. It is
not difficult to believe that the Indians easily shoot great numbers in
remote valleys that have not been hunted for years.

The extreme conditions of life existing on these lofty plateaus are well
shown by the readiness with which even the hardy shepherds avail
themselves of shelter. Wherever deep valleys bring a milder climate
within reach of the pastures the latter are unpopulated for miles on
either side. The sixty-mile stretch between Chuquibamba and Salamanca is
without even a single hut, though there are pastures superior to the
ones occupied by those loftiest huts of all. Likewise there are no
permanent homes between Salamanca and Cotahuasi, though the shepherds
migrate across the belt in the milder season of rain. Eastward and
northward toward the crest of the Maritime Cordillera there are no huts
within a day’s journey of the Cotahuasi canyon. Then there is a group of
a dozen just under the crest of the secondary range that parallels the
main chain of volcanoes. Thence northward there are a number of
scattered huts between 15,500 and 16,500 feet (4,700 and 5,000 m.),
until we reach the highest habitations of all at 17,100 feet (5,210m.).

[Illustration: FIG. 26--Regional diagram to show the physical relations
in the lava plateau of the Maritime Cordillera west of the continental
divide. For location, see Fig. 20. Trails lead up the intrenched
tributaries. If the irrigated bench (lower right corner) is large, a
town will be located on it. Shepherds’ huts are scattered about the edge
of the girdle of spurs. There is also a string of huts in the deep
sheltered head of each tributary. See also Fig. 29 for conditions on the
valley or canyon floor.]

The unpopulated belts of lava plateau bordering the entrenched valleys
are, however, as distinctly “sustenance” spaces, to use Penck’s term, as
the irrigated and fertile alluvial fans in the bottom of the valley.
This is well shown when the rains come and flocks of llamas and sheep
are driven forth from the valleys to the best pastures. It is equally
well shown by the distribution of the shepherds’ homes. These are not
down on the warm canyon floor, separated by a half-day’s journey from
the grazing. They are in the intrenched tributary valleys of Figure 26
or just within the rim of the canyon. It is not shelter from the cold
but from the wind that chiefly determines their location. They are also
kept near the rim of the canyon by the pressure of the farming
population from below. Every hundred feet of descent from the arid
plateau (Fig. 29) increases the water supply. Springs increase in number
and size; likewise belts of seepage make their appearance. The gradients
in many places diminish, and flattish spurs and shoulders interrupt the
generally steep descents of the canyon wall. Every change of this sort
has a real value to the farmer and means an enhanced price beyond the
ability of the poor shepherd to pay. If you ask a wealthy _hacendado_ on
the valley floor (Fig. 29), who it is that live in the huts above him,
he will invariably say “los Indios,” with a shrug meant to convey the
idea of poverty and worthlessness. Sometimes it is “los Indios pobres,”
or merely “los pobres.” Thus there is a vertical stratification of
society corresponding to the superimposed strata of climate and land.

At Salamanca (Fig. 62) I saw this admirably displayed under
circumstances of unusual interest. The floor and slopes of the valley
are more completely terraced than in any other valley I know of. In the
photograph, Fig. 30, which shows at least 2,500 feet of descent near the
town, one cannot find a single patch of surface that is not under
cultivation. The valley is simply filled with people to the limit of its
capacity. Practically all are Indians, but with many grades of wealth
and importance. When we rode out of the valley before daybreak, one
September morning in 1911, there was a dead calm, and each step upward
carried us into a colder stratum of air. At sunrise we had reached a
point about 2,000 feet above the town, or 14,500 feet (4,420 m.) above
sea level. We stood on the frost line. On the opposite wall of the
valley the line was as clearly marked out as if it had been an
irrigating canal. The light was so fully reflected from the millions of
frost crystals above it that both the mountainside and the valley slopes
were sparkling like a ruffled lake at sunrise. Below the frost line the
slopes were dark or covered with yellow barley and wheat stubble or
green alfalfa.

It happened that the frost line was near the line of division between
corn and potato cultivation and also near the line separating the steep
rough upper lands from the cultivable lower lands. Not a habitation was
in sight above us, except a few scattered miserable huts near broken
terraces, gullied by wet-weather streams and grown up to weeds and
brush. Below us were well-cultivated fields, and the stock was kept in
bounds by stone fences and corrals; above, the half-wild burros and
mules roamed about everywhere, and only the sheep and llamas were in
rude enclosures. Thus in a half hour we passed the frontier between the
agricultural folk below the frost line and the shepherd folk above it.

[Illustration: FIG. 27--Terraced valley slopes at Huaynacotas, Cotahuasi
Valley, Peru. Elevation 11,500 feet (3,500 m.).]

[Illustration: FIG. 28--The highly cultivated and thoroughly terraced
floor of the Ollantaytambo Valley at Ollantaytambo. This is a tributary
of the Urubamba; elevation, 11,000 feet.]

[Illustration: FIG. 29--Cotahuasi on the floor of the Cotahuasi canyon.
The even skyline of the background is on a rather even-topped lava
plateau. The terrace on the left of the town is formed on limestone,
which is overlain by lava flows. A thick deposit of terraced alluvium
may be seen on the valley floor, and it is on one of the lower terraces
that the city of Cotahuasi stands. The higher terraces are in many cases
too dry for cultivation. The canyon is nearly 7,000 feet (2,130 m.) deep
and has been cut through one hundred principal lava flows.]

In a few spots the line followed an irregular course, as where flatter
lands were developed at unusual elevations or where air drainage altered
the normal temperature. And at one place the frost actually stood on
the young corn, which led us to speculate on the possibility of securing
from Salamanca a variety of maize that is more nearly resistant to light
frosts than any now grown in the United States. In the endless and
largely unconscious experimentation of these folk perched on the valley
walls a result may have been achieved ahead of that yet reached by our
professional experimenters. Certain it is that nowhere else in the world
has the potato been grown under such severe climatic conditions as in
its native land of Peru and Bolivia. The hardiest varieties lack many
qualities that we prize. They are small and bitter. But at least they
will grow where all except very few cultivated plants fail, and they are
edible. Could they not be imported into Canada to push still farther
northward the limits of cultivation? Potatoes are now grown at Forts
Good Hope and McPherson in the lower Mackenzie basin. Would not the
hardiest Peruvian varieties grow at least as far north as the
continental timber line? I believe they could be grown still farther
north. They will endure repeated frosts. They need scarcely any
cultivation. Prepared in the Peruvian manner, as _chuño_, they could be
kept all winter. Being light, the meal derived from them could be easily
packed by hunters and prospectors. An Indian will carry in a pouch
enough to last him a week. Why not use it north of the continental limit
of other cultivated plants since it is the pioneer above the frost line
on the Peruvian mountains?

The relation between farmer and shepherd or herdsman grows more complex
where deeper valleys interrupt the highlands and mountains. The
accompanying sketch, Fig. 32, represents typical relations, though based
chiefly on the Apurimac canyon and its surroundings near Pasaje. First
there is the snow-clad region at the top of the country. Below it are
grassy slopes, the homes of mountain shepherds, or rugged mountain
country unsuited for grazing. Still lower there is woodland, in patches
chiefly, but with a few large continuous tracts. The shady sides of the
ravines and the mountains have the most moisture, hence bear the densest
growths. Finally, the high country terminates in a second belt of
pasture below the woodland.

[Illustration: FIG. 32--Regional diagram representing the deep canyoned
country west of the Eastern Cordillera in the region of the Apurimac.
For photograph see Fig. 94. For further description see note on regional
diagrams, p. 51. Numbers 1, 2, and 3 correspond in position to the same
numbers in Fig. 33.]

[Illustration: FIG. 30--Terraced hill slopes near Salamanca. There is no
part of the photograph which is not covered with terraces save a few
places where bushy growths are visible or where torrents descend through
artificial canals.]

[Illustration: FIG. 31--Alpine pastures in the mountain valley between
Chuquibambilla and Lambrama. Huge stone corrals are built on either
slope, sheltered from the night winds that blow down-valley.]

Whenever streams descend from the snow or woodland country there is
water for the stock above and for irrigation on the alluvial fan below.
But the spur ends dropping off abruptly several thousand feet have a
limited area and no running streams, and the ground water is hundreds of
feet down. There is grass for stock, but there is no water. In some
places the stock is driven back and forth every few days. In a few
places water is brought to the stock by canal from the woodland streams
above, as at Corralpata.[7] In the same way a canal brings water to
Pasaje hacienda from a woodland strip many miles to the west. The little
canal in the figure is almost a toy construction a few inches wide and
deep and conveying only a trickle of water. Yet on it depends the
settlement at the spur end, and if it were cut the people would have to
repair it immediately or establish new homes.

[Illustration: FIG. 33--Valley climates of the canyoned region shown in
Fig. 32.]

The canal and the pasture are possible because the slopes are moderate.
They were formed in an earlier cycle of erosion when the land was lower.
They are hung midway between the rough mountain slopes above and the
steep canyon walls below (Fig. 32). Their smooth descents and gentle
profiles are in very pleasing contrast to the rugged scenery about them.
The trails follow them easily. Where the slopes are flattest, farmers
have settled and produce good crops of corn, vegetables, and barley.
Some farmers have even developed three-and four-story farms. On an
alluvial fan in the main valley they raise sugar cane and tropical and
subtropical fruits; on the flat upper slopes they produce corn; in the
moister soil near the edge of the woodland are fields of mountain
potatoes; and the upper pastures maintain flocks of sheep. In one
district this change takes place in a distance that may be covered in
five hours. Generally it is at least a full and hard day’s journey from
one end of the series to the other.

Wherever these features are closely associated they tend to be
controlled by the planter in some deep valley thereabouts. Where they
are widely scattered the people are independent, small groups living in
places nearly inaccessible. Legally they are all under the control of
the owners of princely tracts that take in the whole country, but the
remote groups are left almost wholly to themselves. In most cases they
are supposed to sell their few commercial products to the _hacendado_
who nominally owns their land, but the administration of this
arrangement is left largely to chance. The shepherds and small farmers
near the plantation are more dependent upon the planter for supplies,
and also their wants are more varied and numerous. Hence they pay for
their better location in free labor and in produce sold at a discount.

So deep are some of the main canyons, like the Apurimac and the
Cotahuasi, that their floors are arid or semi-arid. The fortunes of
Pasaje are tied to a narrow canal from the moist woodland and a tiny
brook from a hollow in the valley wall. Where the water has thus been
brought down to the arable soil of the fans there are rich plantations
and farms. Elsewhere, however, the floor is quite dry and uncultivated.
In small spots here and there is a little seepage, or a few springs, or
a mere thread of water that will not support a plantation, wherefore
there have come into existence the valley herdsmen and shepherds. Their
intimate knowledge of the moist places is their capital, quite as much
as are the cattle and sheep they own. In a sense their lands are the
neglected crumbs from the rich man’s table. So we find the shepherd from
the hills invading the valleys just as the valley farmer has invaded the
country of the shepherd.

[Illustration: FIG. 34--Regional diagram to show the typical physical
conditions and relations in an intermont basin in the Peruvian Andes.
The Cuzco basin (see Fig. 37) is an actual illustration; it should,
however, be emphasized that the diagram is not a “map” of that basin,
for whilst conditions there have been utilized as a basis, the
generalization has been extended to illustrate many basins.]

The basin type of topography calls into existence a set of relations
quite distinct from either of those we have just described. Figure 34
represents the main facts. The rich and comparatively flat floor of the
basin supports most of the people. The alluvial fans tributary thereto
are composed of fine material on their outer margin and of coarse stony
waste at their heads. Hence the valley farms also extend over the edges
of the fans, while only pasture or dense chaparral occupies the upper
portions. Finally there is the steep margin of the basin where the
broad and moderate slopes of the highland break down to the floor of the
basin.

[Illustration: FIG. 35--Climatic cross-section showing the location of
various zones of cultivation and pasture in a typical intermont basin in
the Peruvian Andes. The thickness of the dark symbols on the right is
proportional to the amount of each staple that is produced at the
corresponding elevation. See also the regional diagram Fig. 34.]

If a given basin lies at an elevation exceeding 14,000 feet (4,270 m.),
there will be no cultivation, only pasture. If at 10,000 or 11,000 feet
(3,000 or 3,350 m.), there will be grain fields below and potato fields
above (Figs. 34 and 35). If still lower, fruit will come in and finally
sugar cane and many other subtropical products, as at Abancay. Much will
also depend upon the amount of available water and the extent of the
pasture land. Thus the densely populated Cuzco basin has a vast mountain
territory tributary to it and is itself within the limits of barley and
wheat cultivation. Furthermore there are a number of smaller basins,
like the Anta basin on the north, which are dependent upon its better
markets and transportation facilities. A dominance of this kind is
self-stimulating and at last is out of all proportion to the original
differences of nature. Cuzco has also profited as the gateway to the
great northeastern valley region of the Urubamba and its big
tributaries. All of the varied products of the subtropical valleys find
their immediate market at Cuzco.

The effect of this natural conspiracy of conditions has been to place
the historic city of Cuzco in a position of extraordinary importance.
Hundreds of years before the Spanish Conquest it was a center of
far-reaching influence, the home of the powerful Inca kings. From it the
strong arm of authority and conquest was extended; to it came tribute
of grain, wool, and gold. To one accustomed to look at such great
consequences as having at least some ultimate connection with the earth,
the situation of Cuzco would be expected to have some unique features.
With the glorious past of that city in mind, no one can climb to the
surrounding heights and look down upon the fertile mountain-rimmed plain
as at an ordinary sight (Fig. 37). The secret of those great conquests
lies not only in mind but in matter. If the rise of the Incas to power
was not related to the topography and climate of the Cuzco basin, at
least it is certain that without so broad and noble a stage the scenes
would have been enacted on a far different scale.

The first Inca king and the Spanish after the Incas found here no mobile
nomadic tribes melting away at the first touch, no savages hiding in
forest fastnesses, but a well-rooted agricultural race in whose center a
large city had grown up. Without a city and a fertile tributary plain no
strong system of government could be maintained or could even arise. It
is a great advantage in ruling to have subjects that cannot move. The
agricultural Indians of the Andean valleys and basins, in contrast to
the mobile shepherd, are as fixed as the soil from which they draw their
life.

The full occupation of the pasture lands about the Cuzco basin is in
direct relation to the advantages we have already enumerated. Every part
of the region feels the pressure of population. Nowhere else in the
Peruvian Andes are the limits between cultivation and grazing more
definitely drawn than here. Moreover, there is today a marked difference
between the types that inhabit highland and basin. The basin Indian is
either a debauched city dweller or, as generally, a relatively alert
farmer. The shepherds are exceedingly ignorant and live for the most
part in a manner almost as primitive as at the time of the Conquest.
They are shy and suspicious. Many of them prefer a life of isolation and
rarely go down to the town. They live on the fringe of culture. The new
elements of their life have come to them solely by accident and by what
might be called a process of ethnic seepage. The slight advances that
have been made do not happen by design, they merely happen. Put the
highland shepherd in the basin and he would starve in competition with
the basin type. Undoubtedly he would live in the basin if he could. He
has not been driven out of the basin; he is kept out.

And thus it is around the border of the Abancay basin and others like
it. Only, the Abancay basin is lower and more varied as to resources.
The Indian is here in competition with the capitalistic white planter.
He lives on the land by sufferance alone. Farther up the slopes are the
farms of the Indians and above them are the pastures of the ignorant
shepherds. Whereas the Indian farmer who raises potatoes clings chiefly
to the edge of the Cuzco basin where lie the most undesirable
agricultural lands, the Indian farmers of Abancay live on broad rolling
slopes like those near the pass northward toward Huancarama. They are
unusually prosperous, with fields so well cultivated and fenced, so
clean and productive, that they remind one somewhat of the beautiful
rolling prairies of Iowa.

It remains to consider the special topographic features of the mountain
environments we are discussing, in the Vilcapampa region on the eastern
border of the Andes (Fig. 36). The Cordillera Vilcapampa is
snow-crested, containing a number of fine white peaks like Salcantay,
Soray, and Soiroccocha (Fig. 140). There are many small glaciers and a
few that are several miles long. There was here in glacial times a much
larger system of glaciers, which lived long enough to work great changes
in the topography. The floors of the glaciated valleys were smoothed and
broadened and their gradients flattened (Figs. 137 and 190). The side
walls were steepened and precipitous cirques were formed at the valley
heads. Also, there were built across the valleys a number of stony
morainic ridges. With all these changes there was, however, but little
effect upon the main masses of the big intervalley spurs. They remain as
before--bold, wind-swept, broken, and nearly inaccessible.

[Illustration: FIG. 36--Regional diagram for the Eastern Cordillera or
Cordillera Vilcapampa. Note the crowded zones on the right (east and
north) in contrast to the open succession on the left. In sheltered
places woodland extends even higher than shown. At several points
patches of it grow right under the snowline. Other patches grow on the
floors of the glaciated valley troughs.]

The work of the glaciers aids the mountain people. The stony moraines
afford them handy sizable building material for their stone huts and
their numerous corrals. The thick tufts of grass in the marshy spots in
the overdeepened parts of the valleys furnish them with grass for their
thatched roofs. And, most important of all, the flat valley floors have
the best pasture in the whole mountain region. There is plenty of water.
There is seclusion, and, if a fence be built from one valley wall to
another as can be done with little labor, an entire section of the
valley may be inclosed. A village like Choquetira, located on a bench on
the valley side, commands an extensive view up and down the valley--an
important feature in a grazing village where the corrals cannot always
be built near the houses of the owners. Long, finger-like belts of
highland-shepherd population have thus been extended into the mountain
valleys. Sheep and llamas drift right up to the snowline.

There is, however, a marked difference between the people on opposite
sides of the Cordillera Vilcapampa. On the west the mountains are
bordered by a broad highland devoted to grazing. On the east there is a
narrower grazing belt leading abruptly down to tropical valleys. The
eastern or leeward side is also the warmer and wetter side of the
Cordillera. The snowline is several hundred feet lower on the east. The
result is that patches of scrub and even a little woodland occur almost
at the snowline in favored places. Mist and storms are more frequent.
The grass is longer and fresher. Vegetation in general is more abundant.
The people make less of wool than of cattle, horses, and mules.
Vilcabamba pueblo is famous for its horses, wiry, long-haired little
beasts, as hardy as Shetland ponies. We found cattle grazing only five
hundred feet below the limit of perpetual snow. There are cultivated
spots only a little farther down, and only a thousand feet below the
snow are abandoned terraces. At the same elevation are twisted quenigo
trees, at least two hundred years old, as shown by their rings of
growth. Thus the limits of agriculture are higher on the east; likewise
the limits of cattle grazing that naturally goes with agriculture. Sheep
would thrive, but llamas do better in drier country, and the shepherd
must needs mix his flocks, for the wool which is his chief product
requires transportation and only the cheap and acclimated llama is at
the shepherd’s disposal. From these facts it will be seen that the
anthropo-geographic contrasts between the eastern and western sides of
the Cordillera Vilcapampa are as definite as the climatic and vegetal
contrasts. This is especially well shown in the differences between dry
Arma, deep-sunk in a glaciated valley west of the crest of the
mountains, and wet Puquiura, a half-day’s journey east of the crest.
There is no group on the east at all comparable to the shepherds of
Choquetira, either in the matter of thorough-going dependence upon
grazing or in that of dependence upon glacial topography.

[Illustration: FIG. 37--Cuzco and a portion of the famous Cuzco basin
with bordering grassy highlands.]

[Illustration: FIG. 38--Terraced valley slopes and floor, Urubamba
Valley between Urubamba and Ollantaytambo.]

[Illustration: FIG. 39--Huichihua, near Chuquibambilla, a typical
mountain village, in the valleys of the Central Ranges, Peruvian Andes.]

[Illustration: FIG. 40--Potato fluid above Vilcabamba at 12,000 feet
(3,660 m.). The natural sod is broken by a steel-shod stick and the seed
potato dropped into a mere puncture. It receives no attention thereafter
until harvest time.]

Topography is not always so intimately related to the life of the people
as here. In our own country the distribution of available water is a far
greater factor. The Peruvian Andes therefore occupy a distinctive place
in geography, since, more nearly than in most mountains, their physical
conditions have typical human relations that enable one clearly to
distinguish the limits of control of each feature of climate or relief.

CHAPTER VI

THE BORDER VALLEYS OF THE EASTERN ANDES

[Illustration: FIG. 41--Regional diagram of the eastern aspect of the
Cordillera Vilcapampa. See also Fig. 17 of which this is an enlarged
section.]

On the northeastern border of the Peruvian Andes long mountain spurs
trail down from the regions of snow to the forested plains of the
Amazon. Here are the greatest contrasts in the physical and human
geography of the Andean Cordillera. So striking is the fact that every
serious student of Peru finds himself compelled to cross and recross
this natural frontier. The thread of an investigation runs irregularly
now into one border zone, now into another. Out of the forest came the
fierce marauders who in the early period drove back the Inca pioneers.
Down into the forest to escape from the Spaniards fled the last Inca and
his fugitive court. Here the Jesuit fathers sowed their missions along
the forest margin, and watched over them for two hundred years. From the
mountain border one rubber project after another has been launched into
the vast swampy lowlands threaded by great rivers. As an ethnic boundary
the eastern mountain border of Peru and Bolivia has no equal elsewhere
in South America. From the earliest antiquity the tribes of the
grass-covered mountains and the hordes of the forested plains have had
strongly divergent customs and speech, that bred enduring hatred and led
to frequent and bloody strife.

[Illustration: FIG. 42--Rug weaver at Cotahuasi. The industry is limited
to a small group of related families, living in the Cotahuasi Canyon
near Cotahuasi. The rugs are made of alpaca wool. Pure black, pure
white, and various shades of mixed gray wool are employed. The result is
that the rugs have “fast” colors that always retain their original
contrasts. They are made only to order at the homes of the purchasers.
The money payment is small, but to it is added board and lodging,
besides tobacco, liqueurs, and wine. Before drinking they dip their
finger-tips in the wine and sprinkle the earth “that it may be
fruitful,” the air “that it may be warm,” the rug “that it may turn out
well,” and finally themselves, making the sign of the cross. Then they
set to work.]

[Illustration: FIG. 43--The floor of the Urubamba Valley from Tarai. The
work of the glaciers was not confined to the lofty situations. Mountain
débris was delivered to all the streams, many of which aggraded their
floors to a depth of several hundred feet, thus increasing the extent of
arable soil at elevations where a less rigorous climate permits the
production of crops and encourages intensive cultivation.]

On the steepest spurs of the Pampaconas Valley the traveler may go from
snow to pasture in a half day and from pasture to forest in the same
time. Another day he is in the hot zone of the larger valley floors, the
home of the Machigangas. The steep descents bring out the superimposed
zones with diagrammatic simplicity. The timber line is as sharply marked
as the edge of a cultivated field. At a point just beyond the huts of
Pampaconas one may stand on a grassy spur that leads directly up--a
day’s journey--to the white summits of the Cordillera Vilcapampa. Yet so
near him is the edge of the forest that he is tempted to try to throw a
stone into it. In an hour a bitter wind from the mountains may drive him
to shelter or a cold fog come rolling up from the moist region below. It
is hard to believe that oppressive heat is felt in the valley just
beneath him.

In the larger valleys the geographic contrasts are less sharp and the
transition from mountains to plain, though less spectacular, is much
more complex and scientifically interesting. The forest types
interfinger along the shady and the sunny slopes. The climate is so
varied that the forest takes on a diversified character that makes it
far more useful to man. The forest Indians and the valley planters are
in closer association. There are many islands and peninsulas of plateau
population on the valley floor. Here the zones of climate and the belts
of fertile soil have larger areas and the land therefore has greater
economic value. Much as the valley people need easier and cheaper
communication with the rest of Peru it is no exaggeration to say that
the valley products, are needed far more by the coast and plateau
peoples to make the republic self-supporting. Coca, wood, sugar, fruit,
are in such demand that their laborious and costly transportation from
the valleys to the plateau is now carried on with at least some profit
to the valley people. Improved transportation would promote travel and
friendship and supply a basis for greater political unity.

A change in these conditions is imminent. Years ago the Peruvian
government decreed the construction of a railway from Cuzco to Santa Ana
and preliminary surveys were made but without any immediate practical
effect. By June, 1914, 12.4 miles (20 km.) had been opened to traffic.
The total length of the proposed line is 112 miles (180 km.), the gauge
is to be only 2.46 feet (75 cm.),[8] and the proposed cost several
millions of dollars. The financial problem may be solved either by a
diversion of local revenues, derived from taxes on coca and alcohol, or
by borrowed foreign capital guaranteed by local revenues.

A shrubby vegetation is scattered along the valley from the village of
Urubamba, 12,000 feet (3,658 m.) above sea level, to the Canyon of
Torontoy. It is local and of little value. Trees appear at
Ollantaytambo, 11,000 feet (3,353 m.), and here too are more extensive
wheat and maize fields besides throngs of cacti and great patches of
wild geraniums. On our valley journey we camped in pleasant fields
flanked by steep hills whose summits each morning were tipped with snow.
Enormous alluvial fans have partly filled up the valleys and furnished
broad tracts of fertile soil. The patient farmers have cleared away the
stones on the flatter portions and built retaining walls for the smooth
fields required for irrigation. In places the lower valley slopes are
terraced in the most regular manner (Fig. 38). Some of the fans are too
steep and stony for cultivation, exposing bare tracts which wash down
and cover the fields. Here and there are stone walls built especially to
retain the rush of mud and stones that the rains bring down. Many of
them were overthrown or completely buried. Unless the stream channels on
the fans are carefully watched and effective works kept up, the labor of
years may be destroyed in a single slide from the head of a steep fan.

Each group of fans has a population proportioned to its size and
fertility. If there are broad expanses a town like Urubamba or a great
hacienda like Huadquiña is sure to be found. One group of huge stony
fans below Urubamba (Fig. 180) has only a thin population, for the soil
is coarse and infertile and the rivers deeply intrenched. In some places
the tiny fans perched high upon the flanks of the mountains where little
tributaries burst out of steep ravines are cultivated by distant owners
who also till parts of the larger fans on the main valley floors.
Between the fans of the valley bottoms and the smooth slopes of the high
plateaus are the unoccupied lands--the steep canyon walls. Only in the
most highly favored places where a small bench or a patch of alluvium
occurs may one find even an isolated dwelling. The stair-like trails, in
some places cut in solid rock, zigzag up the rocky slopes. An ascent of
a thousand feet requires about an hour’s travel with fresh beasts. The
valley people are therefore walled in. If they travel it is surely not
for pleasure. Even business trips are reduced to the smallest number.
The prosperity and happiness of the valley people are as well known
among the plateau people as is their remarkable bread. Their climate has
a combination of winter rain and winter cold with light frosts that is
as favorable for good wheat as the continuous winter cold and snow cover
of our northern Middle West. The colder grainfields of the plateau are
sowed to barley chiefly, though there is also produced some wheat.
Urubamba wheat and bread are exported in relatively large quantities,
and the market demands greater quantities than the valley can supply.
Oregon and Washington flour are imported at Cuzco, two days’ muleback
journey from the wheat fields of Urubamba.

Such are the conditions in the upper Urubamba Valley. The lower valley,
beginning at Huadquiña, is 8,000 feet (2,440 m.) above sea level and
extends down to the two-thousand-foot contour at Rosalina and to one
thousand feet (305 m.) at Pongo de Mainique. The upper and lower
sections are only a score of miles (30 km.) apart between Huadquiña and
Torontoy, but there is a difference in elevation of three thousand feet
(915 m.) at just the level where the maximum contrasts are produced. The
cold timber line is at 10,500 feet (3,200 m.).[9] Winter frosts are
common at the one place; they are absent altogether at the other.
Torontoy produces corn; Huadquiña produces sugar cane.

These contrasts are still further emphasized by the sharp topographic
break between the two unlike portions of the valley. A few miles below
Torontoy the Urubamba plunges into a mile-deep granite canyon. The walls
are so close together that it is impossible from the canyon floor to get
into one photograph the highest and steepest walls. At one place there
is over a mile of descent in a horizontal distance of 2,000 feet. Huge
granite slabs fall off along joint planes inclined but 15° from the
vertical. The effect is stupendous. The canyon floor is littered with
coarse waste and the gradient of the river greatly steepened. There is
no cultivation. The trees cling with difficulty to patches of rock waste
or to the less-inclined slopes. There is a thin crevice vegetation that
outlines the joint pattern where seepage supplies the venturesome roots
with moisture. Man has no foothold here, save at the top of the country,
as at Machu Picchu, a typical fortress location safeguarded by the
virtually inaccessible canyon wall and connected with the main ridge
slopes only by an easily guarded narrow spur. Toward the lower end of
the canyon a little finer alluvium appears and settlement begins.
Finally, after a tumble of three thousand feet over countless rapids the
river emerges at Colpani, where an enormous mass of alluvium has been
dumped. The well-intrenched river has already cut a large part of it
away. A little farther on is Huadquiña in the Salcantay Valley, where a
tributary of the Urubamba has built up a sheet of alluvial land, bright
green with cane. From the distant peaks of Salcantay and its neighbors
well-fed streams descend to fill the irrigation channels. Thus the snow
and rock-waste of the distant mountains are turned into corn and sugar
on the valley lowlands.

[Illustration: FIG. 44--The snow-capped Cordillera Vilcapampa north of
Yucay and the upper canyon of the Urubamba from the wheat fields near
Chinchero. In the foreground is one of the well-graded mature slopes of
Fig. 123. The crests of the mountains lie along the axis of a granite
intrusion. The extent of the snowfields is extraordinary in view of the
low latitude, 13° S.]

[Illustration: FIG. 45--Rounded slopes due to glacial action at
Pampaconas in the Pampaconas Valley near Vilcabamba. A heavy tropical
forest extends up the Pampaconas Valley to the hill slopes in the
background. Its upper limit of growth is about 10,000 feet (3,050 m.).
The camera is pointed slightly downhill.]

[Illustration: FIG. 46--Hacienda Huadquiña in the Salcantay Valley a
short distance above its junction with the Urubamba, elevation 8,000
feet (2,440 m.). The cultivated fields are all planted to sugar cane.
The mountain slopes are devoted to grazing.]

The Cordillera Vilcapampa is a climatic as well as a topographic
barrier. The southwestern aspect is dry; the northeastern aspect
forested. The gap of the canyon, it should be noticed, comes at a
critical level, for it falls just above the upper border of the zone of
maximum precipitation. The result is that though mists are driven
through the canyon by prolonged up-valley winds, they scatter on
reaching the plateau or gather high up on the flanks of the valley or
around the snowy peaks overlooking the trail between Ollantaytambo and
Urubamba. The canyon walls are drenched with rains and even some of the
lofty spurs are clothed with dense forest or scrub.

Farther down the valley winds about irregularly, now pushed to one side
by a huge alluvial fan, now turned by some resistant spur of rock.
Between the front range of the Andes and the Cordillera Vilcapampa there
is a broad stretch of mountain country in the lee of the front range
which rises to 7,000 feet (2,134 m.) at Abra Tocate (Fig. 15), and falls
off to low hills about Rosalina. It is all very rough in that there are
nowhere any flats except for the narrow playa strips along the streams.
The dense forest adds to the difficulty of movement. In general
appearance it is very much like the rugged Cascade country of Oregon
except that the Peruvian forest is much more patchy and its trees are in
many places loaded with dense dripping moss which gives the landscape a
somber touch quite absent from most of the forests of the temperate
zone.

The fertility of the eastern valleys of Peru--the result of a union of
favorable climate and alluvial soil--has drawn the planter into this
remote section of the country, but how can he dispose of his products?
Even today with a railway to Cuzco from the coast it is almost
impossible for him to get his sugar and cacao to the outside world.[10]
How did he manage before even this railway was built? How could the
eastern valley planter live before there were any railways at all in
Peru? In part he has solved the problem as the moonshiner of Kentucky
tried to solve it, and from cane juice makes aguardiente (brandy). The
latter is a much more valuable product than sugar, hence (1) it will
bear a higher rate of transportation, or (2) it will at the same rate of
transportation yield a greater net profit. In a remote valley where
sugar could not be exported on account of high freight rates brandy
could still be profitably exported.

The same may be said for coca and cacao. They are condensed and valuable
products. Both require more labor than sugar but are lighter in bulk and
thus have to bear, in proportion to their value, a smaller share of the
cost of transportation. At the end of three years coca produces over a
ton of leaves per acre per year, and it can be made to produce as much
as two tons to the acre. The leaves are picked four times a year. They
are worth from eight to twelve cents gold a pound at the plantation or
sixteen cents a pound at Cuzco. An orchard of well-cultivated and
irrigated cacao trees will do even better. Once they begin to bear the
trees require relatively little care except in keeping out weeds and
brush and maintaining the water ditches. However, the pods must be
gathered at just the right time, the seeds must be raked and dried with
expert care, and after that comes the arduous labor of the grinding.
This is done by hand on an inclined plane with a heavy round stone whose
corners fit the hand. The chocolate must then be worked into cakes and
dried, or it must be sacked in heavy cowhide and sewed so as to be
practically air tight. When eight or ten years old the trees are mature
and each may then bear a thousand pounds of seed.

[Illustration: FIG. 47--The Urubamba Valley below Paltaybamba. Harder
rocks intruded into the schists that in general compose the valley walls
here form steep scarps. It has been suggested (Davis) that such a
constricted portion of a valley be called a “shut-in.” The old trail
climbed to the top of the valley and over the back of a huge spur. The
new road is virtually a tunnel blasted along the face of a cliff.]

[Illustration: FIG 48--Coca seed beds near Quillabamba, Urubamba Valley.
The young plants are grown under shade and after attaining a height of a
foot or more are gradually accustomed to sunlight and finally
transplanted to the fields that are to become coca orchards.]

If labor were cheap and abundant the whole trend of tropical agriculture
in the eastern valleys would be toward intensive cultivation and the
production of expensive exports. But labor is actually scarce. Every
planter must have agents who can send men down from the plateau towns.
And the planter himself must use his labor to the best advantage.
Aguardiente requires less labor than cacao and coca. The cane costs
about as much in labor the first year as the coca bush or the cacao
tree, but after that much less. The manufacture of brandy from the cane
juice requires little labor though much expensive machinery. For
chocolate, a storehouse, a grinding stone, and a rake are all that
are required. So the planter must work out his own salvation
individually. He must take account of the return upon investments in
machinery, of the number of hands he can command from among the “faena”
or free Indians, of the cost and number of imported hands from the
valley and plateau towns, and, finally, of the transportation rates
dependent upon the number of mules in the neighborhood, and distance
from the market. If in addition the labor is skilfully employed so as to
have the tasks which the various products require fall at different
periods of the year, then the planter may expect to make money upon his
time and get a return upon his initial investment in the land.[11]

[Illustration: FIG. 49--Fig tree formerly attached to a host but now
left standing on its stilt-like aërial roots owing to the decay of the
host.]

[Illustration: FIG. 50--A tiny rubber plant is growing under the tripod
made of yuca stems tied with banana leaves. Growing yuca is shown by the
naked stalks to the left and right of this canopy, and banana plants
fill the background. A plantation scene at Echarati.]

The type of tropical agriculture which we have outlined is profitable
for the few planters who make up the white population of the valleys,
but it has a deplorable effect upon the Indian population. Though the
planters, one and all, complain bitterly of the drunken habits of their
laborers, they themselves put into the hands of the Indians the means of
debauchery. Practically the whole production of the eastern valleys is
consumed in Peru. What the valleys do not take is sent to the plateau,
where it is the chief cause of vicious conduct. Two-thirds of the
prisoners in the city jails are drunkards, and, to be quite plain, they
are virtually supplied with brandy by the planter, who could not
otherwise make enough money. So although the planter wants more and
better labor he is destroying the quality of the little there is, and,
if not actually reducing the quantity of it, he is at least very
certainly reducing the rate of increase.

The difficulties of the valley planter could be at least partly overcome
in several ways. The railway will reduce transportation costs,
especially when the playas of the valleys are all cleared and the
exports increased. Moreover the eastern valleys are capable of
producing things of greater utility than brandy and coca leaves. So far
as profits are increased by cheaper transportation we may expect the
planter to produce more rather than less of brandy and coca, his two
most profitable exports, unless other products can be found that are
still more profitable. The ratio of profits on sugar and brandy will
still be the same unless the government increases the tax on brandy
until it becomes no more profitable than sugar. That is what ought to be
done for the good of the Indian population. It cannot be done safely
without offering in its place the boon of cheaper railway transportation
for the sugar crop. Furthermore, with railway improvements should go the
blessings that agricultural experiments can bestow. A government farm in
a suitable place would establish rice and cotton cultivation. Many of
the playas or lower alluvial lands along the rivers can be irrigated.
Only a small fraction of the water of the Rio Urubamba is now turned out
upon the fields. For a large part of the year the natural rainfall would
suffice to keep rice in good condition. Six tons a year are now grown on
Hacienda Sahuayaco for local use on account of the heavy rate on rice
imported on muleback from Cuzco, whither it comes by sea and by trail
from distant coastal valleys. The lowland people also need rice and it
could be sent to them down river by an easier route than that over which
their supplies now come. It should be exported to the highlands, not
imported therefrom. There are so many varieties adapted to so many kinds
of soil and climate that large amounts should be produced at fair
profits.

The cotton plant, on the other hand, is more particular about climate
and especially the duration of dry and wet seasons; in spite of this its
requirements are all met in the Santa Ana Valley. The rainfall is
moderate and there is an abundance of dry warm soil. The plant could
make most of its growth in the wet season, and the four months of cooler
dry season with only occasional showers would favor both a bright staple
and a good picking season. More labor would be required for cotton and
rice and for the increased production of cacao than under the present
system. This would not be a real difficulty if the existing labor
supply were conserved by the practical abolition, through heavy
taxation, of the brandy that is the chief cause of the laborer’s vicious
habits. This is the first step in securing the best return upon the
capital invested in a railway. Economic progress is here bound up with a
very practical morality. Colonization in the eastern valleys, of which
there have been but a few dismal attempts, will only extend the field of
influence, it will not solve the real problem of bringing the people of
the rich eastern territory of Peru into full and honorable possession of
their natural wealth.

The value of the eastern valleys was known in Inca times, for their
stone-faced terraces and coca-drying patios may still be seen at
Echarati and on the border of the Chaupimayu Valley at Sahuayaco.
Tradition has it that here were the imperial coca lands, that such of
the forest Indians as were enslaved were obliged to work upon them, and
that the leaves were sent to Cuzco over a paved road now covered with
“montaña” or forest. The Indians still relate that at times a
mysterious, wavering, white light appears on the terraces and hills
where old treasure lies buried. Some of the Indians have gold and silver
objects which they say were dug from the floors of hill caves. There
appears to have been an early occupation of the best lands by the
Spaniards, for the long extensions down them of Quechua population upon
which the conquerors could depend no doubt combined with the special
products of the valley to draw white colonists thither.[12] General
Miller,[13] writing in 1836, mentions the villages of Incharate
(Echarati) and Sant’ Ana (Santa Ana) but discourages the idea of
colonization “... since the river ... has lofty mountains on either
side of it, and is not navigable even for boats.”

In the “Itinerario de los viajes de Raimondi en el Peru”[14] there is an
interesting account of the settlement by the Rueda family of the great
estate still held by a Rueda, the wife of Señor Duque. José Rueda, in
1829, was a government deputy representative and took his pay in land,
acquiring valuable territory on which there was nothing more than a
mission. In 1830 Rueda ceded certain lands in “arriendo” (rent) and on
these were founded the haciendas Pucamoco, Sahuayaco, etc.

Señor Gonzales, the present owner of Hacienda Sahuayaco, recently
obtained his land--a princely estate, ten miles by forty--for 12,000
soles ($6,000). In a few years he has cleared the best tract, built
several miles of canals, hewed out houses and furniture, planted coca,
cacao, cane, coffee, rice, pepper, and cotton, and would not sell for
$50,000. Moreover, instead of being a superintendent on a neighboring
estate and keeping a shop in Cuzco, where his large family was a source
of great expense, he has become a wealthy landowner. He has educated a
son in the United States. He is importing machinery, such as a rice
thresher and a distilling plant. His son is looking forward to the
purchase of still more playa land down river. He pays a sol a day to
each laborer, securing men from Cotabambas and Abancay, where there are
many Indians, a low standard of wages, little unoccupied land, and a hot
climate, so that the immigrants do not need to become acclimatized.

The deepest valleys in the Eastern Andes of Peru have a semi-arid
climate which brings in its train a variety of unusual geographic
relations. At first as one descends the valley the shady and sunny
slopes show sharply contrasted vegetation.

[Illustration: FIG. 51--Robledo’s mountain-side trail in the Urubamba
Valley below Rosalina.]

[Illustration: FIG. 52--An epiphyte partly supported by a dead host at
Rosalina, elevation 2,000 feet. The epiphyte bears a striking
resemblance to a horned beast whose arched back, tightly clasped
fingers, and small eyes give it a peculiarly malignant and life-like
expression.]

[Illustration: FIG. 53A--The smooth grassy slopes at the junction of the
Yanatili (left) and Urubamba (right) rivers near Pabellon.]

[Illustration: FIG. 53B--Distribution of vegetation in the Urubamba
Valley near Torontoy. The patches of timber in the background occupy the
shady sides of the spurs; the sunny slopes are grass-covered; the valley
floor is filled with thickets and patches of woodland but not true
forest.]

The one is forested, the other grass-covered. Slopes that receive the
noon and afternoon sun the greater part of the year are hottest and
therefore driest. For places in 11° south latitude the sun is well to
the north six months of the year, nearly overhead for about two months,
and to the south four months. Northwesterly aspects are therefore driest
and warmest, hence also grass-covered. In many places the line between
grass and forest is developed so sharply that it seems to be the
artificial edge of a cut-over tract. This is true especially if the
relief is steep and the hill or ridge-crests sharp.[15]

[Illustration: FIG. 54--Climatic cross-section from the crest of the
Cordillera Vilcapampa down the eastern mountain valleys to the tropical
plains.]

At Santa Ana this feature is developed in an amazingly clear manner, and
it is also combined with the dry timber line and with productivity in a
way I have never seen equaled elsewhere. The diagram will explain the
relation. It will be seen that the front range of the mountains is high
enough to shut off a great deal of rainfall. The lower hills and ridges
just within the front range are relatively dry. The deep valleys are
much drier. Each broad expansion of a deep valley is therefore a dry
pocket. Into it the sun pours even when all the surrounding hills and
mountains are wrapped in cloud. The greater number of hours of sunshine
hastens the rate of evaporation and still further increases the dryness.
Under the spur of much sunlight and of ample irrigation water from the
wetter hill slopes, the dry valley pockets produce huge crops of fruit
and cane.

The influence of the local climate upon tree growth is striking. Every
few days, even in the relatively dry winter season, clouds gather about
the hills and there are local showers. The lower limit of the zone of
clouds is sharply marked and at both Santa Ana and Echarati it is
strikingly constant in elevation--about five thousand feet above sea
level. From the upper mountains the forest descends, with only small
patches of glade and prairie. At the lower edge of the zone of cloud it
stops abruptly on the warmer and drier slopes that face the afternoon
sun and continues on the moister slopes that face the forenoon sun or
that slope away from the sun.

But this is not the only response the vegetation makes. The forest
changes in character as well as in distribution. The forest in the wet
zone is dense and the undergrowth luxuriant. In the selective slope
forest below the zone of cloud the undergrowth is commonly thin or
wanting and the trees grow in rather even-aged stands and by species.
Finally, on the valley floor and the tributary fans, there is a distinct
growth of scrub with bands of trees along the water courses. Local
tracts of coarse soil, or less rain on account of a deep “hole” in a
valley surrounded by steeper and higher mountains, or a change in the
valley trend that brings it into less free communication with the
prevailing winds, may still further increase the dryness and bring in a
true xerophytic or drought-resisting vegetation. Cacti are common all
through the Santa Ana Valley and below Sahuayaco there is a patch of
tree cacti and similar forms several square miles in extent. Still
farther down and about half-way between Sahuayaco and Pabellon are
immense tracts of grass-covered mountain slopes (Fig. 53). These extend
beyond Rosalina, the last of them terminating near Abra Tocate (Fig.
15). The sudden interruption is due to a turn in the valley giving
freer access to the up-valley winds that sweep through the pass at Pongo
de Mainique.

[Illustration: FIG. 55--Map to show the relation of the grasslands of
the dry lower portion of the Urubamba Valley (unshaded) to the forested
lands at higher elevations (shaded). See Fig. 54 for climatic
conditions. Patches and slender tongues of woodland occur below the main
timber line and patches of grassland above it.]

Northward from Abra Tocate (Fig. 55) the forest is practically
continuous. The break between the two vegetal regions is emphasized by a
corral for cattle and mules, the last outpost of the plateau herdsmen.
Not three miles away, on the opposite forested slope of the valley, is
the first of the Indian clearings where several families of Machigangas
spend the wet season when the lower river is in flood (Fig. 21). The
grass lands will not yield corn and coca because the soil is too thin,
infertile, and dry. The Indian farms are therefore all in the forest and
begin almost at its very edge. Here finally terminates a long peninsula
of grass-covered country. Below this point the heat and humidity rapidly
increase; the rains are heavier and more frequent; the country becomes
almost uninhabitable for stock; transportation rates double. Here is the
undisputed realm of the forest with new kinds of trees and products and
a distinctive type of forest-dwelling Indian.

At the next low pass is the skull of an Italian who had murdered his
companions and stolen a season’s picking of rubber, attempting to escape
by canoe to the lower Urubamba from the Pongo de Mainique. The
Machigangas overtook him in their swiftest dugouts, spent a night with
him, and the next morning shot him in the back and returned with their
rightful property--a harvest of rubber. For more than a decade
foreigners have been coming down from the plateau to exploit them. They
are an independent and free tribe and have simple yet correct ideas of
right and wrong. Their chief, a man of great strength of character and
one of the most likeable men I have known, told me that he placed the
skull in the pass to warn away the whites who came to rob honest
Indians.

The Santa Ana Valley between the Canyon of Torontoy and the heavy forest
belt below Rosalina is typical of many of the eastern valleys of Peru,
both in its physical setting and in its economic and labor systems.
Westward are the outliers of the Vilcapampa range; on the east are the
smaller ranges that front the tropical lowlands. Steep valleys descend
from the higher country to join the main valley and at the mouth of
every tributary is an alluvial fan. If the alluvium is coarse and
steeply inclined there is only pasture on it or a growth of scrub. If
fine and broad it is cleared and tilled. The sugar plantations begin at
Huadquiña and end at Rosalina. Those of Santa Ana and Echarati are the
most productive. It takes eighteen months for the cane to mature in the
cooler weather at Huadquiña (8,000 feet). Less than a year is required
at Santa Ana (3,400 feet). Patches of alluvium or playas, as they are
locally called, continue as far as Santo Anato, but they are cultivated
only as far as Rosalina. The last large plantation is Pabellon; the
largest of all is Echarati. All are irrigated. In the wet months,
December to March inclusive, there is little or no irrigation. In the
four months of the dry season, June to September inclusive, there is
frequent irrigation. Since the cane matures in about ten months the
harvest seasons fall irregularly with respect to the seasons of rain.
Therefore the land is cleared and planted at irregular intervals and
labor distributed somewhat through the year. There is however a
concentration of labor toward the end of the dry season when most of the
cane is cut for grinding.

The combined freight rate and government tax on coca, sugar, and brandy
take a large part of all that the planter can get for his crop. It is
120 miles (190 km.) from Santa Ana to Cuzco and it takes five days to
make the journey. The freight rate on coca and sugar for mule carriage,
the only kind to be had, is two cents per pound. The national tax is one
cent per pound (0.45 kg.). The coca sells for twenty cents a pound. The
cost of production is unknown, but the paid labor takes probably
one-half this amount. The planter’s time, capital, and profit must come
out of the rest. On brandy there is a national tax of seven cents per
liter (0.26 gallon) and a municipal tax of two and a half cents. It
costs five cents a liter for transport to Cuzco. The total in taxes and
transport is fourteen and a half cents a liter. It sells for twenty
cents a liter. Since brandy (aguardiente), cacao (for chocolate), and
coca leaves (for cocaine) are the only precious substances which the
valleys produce it takes but a moment’s inspection to see how onerous
these taxes would be to the planter if labor did not, as usual, pay the
penalty.

Much of the labor on the plantations is free of cost to the owner and is
done by the so-called _faena_ or free Indians. These are Quechuas who
have built their cabins on the hill lands of the planters, or on the
floors of the smaller valleys. The disposition of their fields in
relation to the valley plantations is full of geographic interest. Each
plantation runs at right angles to the course of the valley. Hacienda
Sahuayaco is ten miles (16 km.) in extent down valley and forty miles
(64 km.) from end to end across the valley, and it is one of the smaller
plantations! It follows that about ten square miles lie on the valley
floor and half of this can ultimately be planted. The remaining three
hundred and ninety square miles include some mountain country with
possible stores of mineral wealth, and a great deal of “fells”
country--grassy slopes, graded though steep, excellent for pasture, with
here and there patches of arable land. But the hill country can be
cultivated only by the small farmer who supplements his supply of food
from cultivated plants like potatoes, corn, and vegetables, by keeping
cattle, mules, pigs, and poultry, and by raising coca and fruit.

The Indian does not own any of the land he tills. He has the right
merely to live on it and to cultivate it. In return he must work a
certain number of days each year on the owner’s plantation. In many
cases a small money payment is also made to the planter. The planter
prefers labor to money, for hands are scarce throughout the whole
eastern valley region. No Indian need work on the planter’s land without
receiving pay directly therefor. Each also gets a small weekly allotment
of aguardiente while in the planter’s employ.

The scene every Saturday night outside the office of the _contador_
(treasurer) of a plantation is a novel one. Several hundred Indians
gather in the dark patio in front of the office. Within the circle of
the feeble candlelight that reaches only the margin of the crowd one may
see a pack of heavy, perspiring faces. Many are pock-marked from
smallpox; here and there an eye is missing; only a few are jovial. A
name is shouted through the open door and an Indian responds. He pulls
off his cap and stands stupid and blinking, while the contador asks:

“Faena” (free)?

“Si, Señor,” he answers.

“Un sol” (one “sol” or fifty cents gold). The assistant hands over the
money and the man gives way to the next one on the list. If he is a
laborer in regular and constant employ he receives five soles (two fifty
gold) per week. There are interruptions now and then. A ragged,
half-drunken man has been leaning against the door post, suspiciously
impatient to receive his money. Finally his name is called.

“Faena?” asks the contador.

“No, Señor, cinco (five) soles.”

At that the field _superintendente_ glances at his time card and speaks
up in protest.

“You were the man that failed to show up on Friday and Saturday. You
were drunk. You should receive nothing.”

“No, mi patrón,” the man contends, “I had to visit a sick cousin in the
next valley. Oh, he was very sick, Señor,” and he coughs harshly as if
he too were on the verge of prostration. The sick cousin, a faena
Indian, has been at work in another cane field on the same plantation
for two days and now calls out that he is present and has never had a
sick day in his life. Those outside laugh uproariously. The contador
throws down two soles and the drunkard is pushed back into the sweating
crowd, jostled right and left, and jeered by all his neighbors as he
slinks away grumbling.

Another Indian seems strangely shy. He scarcely raises his voice above a
whisper. He too is a faena Indian. The contador finds fault.

“Why didn’t you come last month when I sent for you?”

The Indian fumbles his cap, shuffles his feet, and changes his coca cud
from one bulging cheek to the other before he can answer. Then huskily:

“I started, Señor, but my woman overtook me an hour afterward and said
that one of the ewes had dropped a lamb and needed care.”

“But your woman could have tended it!”

“No, Señor, she is sick.”

“How, then, could she have overtaken you?” he is asked.

“She ran only a little way and then shouted to me.”

“And what about the rest of the month?” persists the contador.

“The other lambs came, Señor, and I should have lost them all if I had
left.”

The contador seems at the end of his complaint. The Indian promises to
work overtime. His difficulties seem at an end, but the superintendent
looks at his old record.

“He always makes the same excuse. Last year he was three weeks late.”

So the poor shepherd is fined a sol and admonished that his lands will
be given to some one else if he does not respond more promptly to his
patron’s call for work. He leaves behind him a promise and the rank
mixed smell of coca and much unwashed woolen clothing.

It is not alone at the work that they grumble. There is malaria in the
lower valleys. Some of them return to their lofty mountain homes
prostrated with the unaccustomed heat and alternately shaking with
chills and burning with fever. Without aid they may die or become so
weakened that tuberculosis carries them off. Only their rugged strength
enables the greater number to return in good health.

A plantation may be as large as a principality and draw its laborers
from places fifty miles away. Some of the more distant Indians need not
come to work in the canefields. Part of their flock is taken in place of
work. Or they raise horses and mules and bring in a certain number each
year to turn over to the patron. Hacienda Huadquiña (Fig. 46) takes in
all the land from the snow-covered summits of the Cordillera Vilcapampa
to the canefields of the Urubamba. Within the broad domain are half the
climates and occupations characteristic of Peru. It is difficult to see
how a thousand Indians can be held to even a mixed allegiance. It seems
impossible that word can be got to them. However the native “telegraph”
is even more perfect than that among the forest Indians. From one to the
other runs the news that they are needed in the canefields. On the trail
to and from a mountain village, in their ramblings from one high pasture
to another, within the dark walls of their stone and mud huts when they
gather for a feast or to exchange drinks of brandy and _chicha_--the
word is passed that has come up from the valleys.

For every hundred faena Indians there are five or six regular laborers
on the plantations, so with the short term passed by the faena Indians
their number is generally half that of the total laborers at work at any
one time. They live in huts provided for them by the planter, and in the
houses of their friends among the regular laborers. Here there are
almost nightly carousals. The regular laborer comes from the city or the
valley town. The faena laborer is a small hill farmer or shepherd. They
have much to exchange in the way of clothing, food, and news. I have
frequently had their conversations interpreted for me. They ask about
the flocks and the children, who passed along the trails, what accidents
befell the people.

“Last year,” droned one to another over their chicha, “last year we lost
three lambs in a hailstorm up in the high fields near the snow. It was
very cold. My foot cracked open and, though I have bound it with wet
coca leaves every night, it will not cure,” and he displays his heel,
the skin of which is like horn for hardness and covered with a crust of
dirt whose layers are a record of the weather and of the pools he has
waded for years.

Their wanderings are the main basis of conversation. They know the
mountains better than the condors do. We hired a small boy of twelve at
Puquiura. He was to build our fires, carry water, and help drive the
mules. He crossed the Cordillera Vilcapampa on foot with us. He
scrambled down into the Apurimac canyon and up the ten thousand feet of
ascent on the other side, twisted the tails of the mules, and shouted
more vigorously then the arrieros. He was engaged to go with us to
Pasaje, where his father would return with him in a month. But he
climbed to Huascatay with us and said he wanted to see Abancay. When an
Indian whom we pressed into service dropped the instruments on the trail
and fled into the brush the boy packed them like a man. The soldier
carried a tripod on his back. The boy, not to be outdone, insisted on
carrying the plane table, and to his delight we called him a soldier
too. He went with us to Huancarama. When I paid him he smiled at the
large silver soles that I put into his hand; and when I doubled the
amount for his willingness to work his joy was unbounded. Forthwith he
set out, this time on muleback, on the return journey. The last I saw of
him he was holding his precious soles in a handkerchief and kicking his
beast with his bare heels, as light-hearted as a cavalier. Often I find
myself wondering whether he returned safely with his money. I should
very much like to see him again, for with him I associate cheerfulness
in difficult places and many a pleasant camp-fire.

CHAPTER VII

THE GEOGRAPHIC BASIS OF REVOLUTIONS AND OF HUMAN CHARACTER IN THE
PERUVIAN ANDES

Human character as a spontaneous development has always been a great
factor in shaping historical events, but it is a striking fact that in
the world of our day its influence is exerted chiefly in the lowest and
highest types of humanity. The savage with his fetishes, his taboos, and
his inherent childlikeness and suspicion needs only whim or a slight
religious pretext to change his conduct. Likewise the really educated
and the thoughtful act from motives often wholly unrelated to economic
conditions or results. But the masses are deeply influenced by whatever
affects their material welfare. A purely idealistic impulse may
influence a people, but in time its effects are always displayed against
an economic background.

There is a way whereby we may test this theory. In most places in the
world we have history in the making, and through field studies we can
get an intimate view of it. It is peculiarly the province of geography
to study the present distribution and character of men in relation to
their surroundings and these are the facts of mankind that must forever
be the chief data of economic history. It is not vain repetition to say
that this means, first of all, the study of the character of men in the
fullest sense. It means, in the second place, that a large part of the
character must be really understood. Whenever this is done there is
found a geographic basis of human character that is capable of the
clearest demonstration. It is in the geographic environment that the
material motives of humanity have struck their deepest roots.

These conclusions might be illustrated from a hundred places in the
field of study covered in this book. Almost every chapter of Part I
contains facts of this character. I wish, however, to discuss the
subject specifically and for that purpose now turn to the conditions of
life in the remoter mountain valleys and to one or two aspects of the
revolutions that occur now and then in Peru. The last one terminated
only a few months before our arrival and it was a comparatively easy
matter to study both causes and effects.

A caution is necessary however. It is a pity that we use the term
“revolution” to designate these little disturbances. They affect
sometimes a few, again a few hundred men. Rarely do they involve the
whole country. A good many of them are on a scale much smaller than our
big strikes. Most of them involve a loss of life smaller than that which
accompanies a city riot. They are in a sense strikes against the
government, marked by local disorders and a little violence.

Early in 1911 the Prefect of the Department of Abancay had crowned his
long career by suppressing a revolution. He had been Subprefect at
Andahuaylas, and when the rebels got control of the city of Abancay and
destroyed some of the bridges on the principal trails, he promptly
organized a military expedition, constructed rafts, floated his small
force of men across the streams, and besieged the city. The rebel force
was driven at last to take shelter in the city jail opposite the
Prefectura. There, after the loss of half their number, they finally
surrendered. Seventy-five of them were sent to the government
penitentiary at Arequipa. Among the killed were sons from nearly half
the best families of Abancay. All of the rebels were young men.

It would be difficult to give an adequate idea of the hatred felt by the
townspeople toward the government. Every precaution was taken to prevent
a renewal of the outbreak. Our coming was telegraphed ahead by
government agents who looked with suspicion upon a party of men, well
armed and provisioned, coming up from the Pasaje crossing of the
Apurimac, three days’ journey north. The deep canyon affords shelter not
only to game, but also to fugitives, rebels, and bandits. The government
generally abandons pursuit on the upper edge of the canyon, for only a
prolonged guerilla warfare could completely subdue an armed force
scattered along its rugged walls and narrow floor. The owner of the
hacienda at Pasaje is required to keep a record of all passengers rafted
across the Apurimac, but he explains significantly that some who pass
are too hurried to write their names in his book. Once he reaches the
eastern wall of the canyon a fugitive may command a view of the entire
western wall and note the approach of pursuers. Thence eastward he has
the whole Cordillera Vilcapampa in which to hide. Pursuit is out of the
question.

When we arrived, the venerable Prefect, a model of old-fashioned
courtesy, greeted us with the utmost cordiality. He told us of our
movements since leaving Pasaje, and laughingly explained that since we
had sent him no friendly message and had come from a rebel retreat, he
had taken it for granted that we intended to storm the town. I assured
him that we were ready to join his troops, if necessary, whereupon, with
a delightful frankness, he explained his method of keeping the situation
in hand. Several troops of cavalry and two battalions of infantry were
quartered at the government barracks. Every evening the old gentleman, a
Colonel in the Peruvian army, mounted a powerful gray horse and rode,
quite unattended, through the principal streets of the town. Several
times I walked on foot behind him, again I preceded him, stopping in
shops on the way to make trivial purchases, to find out what the people
had to say about him and the government as he rode by. One old gentleman
interested me particularly. He had only the day before called at the
Prefectura to pay his respects. Although his manner was correct there
was lacking to a noticeable degree the profusion of sentiment that is
apt to be exhibited on such an occasion. He now sat on a bench in a
shop. Both his own son and the shopkeeper’s son had been slain in the
revolution. It was natural that they should be bitter. But the precise
nature of their complaint was what interested me most. One said that he
did not object to having his son lose his life for his country. But that
his country’s officials should hire Indians to shoot his son seemed to
him sheer murder. Later, at Lambrama, I talked with a rebel fugitive,
and that was also his complaint. The young men drafted into the army are
Indians, or mixed, never whites. White men, and men with a small
amount of Indian blood, officer the army. When a revolutionary party
organizes it is of course made up wholly of men of white and mixed
blood, never Indians. The Indians have no more grievance against one
white party than another. Both exploit him to the limit of law and
beyond the limit of decency. He fights if he must, but never by choice.

[Illustration: FIG. 56--The type of forest in the moister tracts of the
valley floor at Sahuayaco. In the center of the photograph is a tree
known as the “sandy matico” used in making canoes for river navigation.]

[Illustration: FIG. 57--Arboreal cacti in the mixed forest of the dry
valley floor below Sahuayaco.]

[Illustration: FIG. 58--Crossing the Apurimac at Pasaje. These are
mountain horses, small and wiry, with a protective coat of long hair.
They are accustomed to graze in the open without shelter during the
entire winter.]

[Illustration: FIG. 59--Crossing the Apurimac at Pasaje. The mules are
blindfolded and pushed off the steep bank into the water and rafted
across.]

Thus Indian troops killed the white rebels of Abancay.

“Tell me, Señor,” said the fugitive, “if you think that just. Tell me
how many Indians you think a white man worth. Would a hundred dead
Indians matter? But how replace a white man where there are so few? The
government _assassinated_ my compatriots!”

“But,” I replied, “why did you fight the government? All of you were
prosperous. Your fathers may have had a grievance against the
government, but of what had you young men to complain?”

His reply was far from convincing. He was at first serious, but his long
abstract statements about taxes and government wastefulness trailed off
into vagueness, and he ended in a laughing mood, talking about
adventure, the restless spirit of young men, and the rich booty of
confiscated lands and property had the rebels won. He admitted that it
was a reckless game, but when I called him a mere soldier of fortune he
grew serious once more and reverted to the iniquitous taxation system of
Peru. Further inquiry made it quite clear that the ill-fated revolution
of Abancay was largely the work of idle young men looking for adventure.
It seemed a pity that their splendid physical energy could not have been
turned into useful channels. The land sorely needs engineers,
progressive ranchmen and farmers, upright officials, and a spirit of
respect for law and order. Old men talked of the unstable character of
the young men of the time, but almost all of them had themselves been
active participants in more than one revolution of earlier years.

Every night at dinner the Prefect sent off by government telegraph a
long message to the President of the Republic on the state of the
Department, and received similar messages from the central government
about neighboring departments. These he read to us, and, curiously
enough, to the entire party, made up of army officers and townsmen. I
was surprised to find later that the company included one government
official whose son had been among the imprisoned rebels at Arequipa. We
met the young man a week later at a mountain village, a day after a
general amnesty had been declared. His escape had been made from the
prison a month before. He forcibly substituted the mess-boy’s clothing
for his own, and thus passed out unnoticed. After a few days’ hiding in
the city, he set out alone across the desert of Vitor, thence across the
lofty volcanic country of the Maritime Andes, through some of the most
deserted, inhospitable land in Peru, and at the end of three weeks had
reached Lambrama, near Abancay, the picture of health!

Later I came to have a better notion of the economic basis of the
revolution, for obviously the planters and the reckless young men must
have had a mutual understanding. Somewhere the rebels had obtained the
sinews of war. The planters did not take an open part in the revolution,
but they financed it. When the rebels were crushed, the planters, at
least outwardly, welcomed the government forces. Inwardly they cursed
them for thwarting their scheme. The reasons have an interesting
geographic basis. Abancay is the center of a sugar region. Great
irrigated estates are spread out along the valley floor and the enormous
alluvial fans built into the main valley at the mouths of the tributary
streams. There is a heavy tax on sugar and on aguardiente (brandy)
manufactured from cane juice. The _hacendados_ had dreamed of lighter
taxes. The rebels offered the means of securing relief. But taxes were
not the real reason for the unrest, for many other sugar producers pay
the tax without serious complaint. Abancay is cut off from the rest of
Peru by great mountains. Toward the west, _via_ Antabamba, Cotahuasi,
and Chuquibamba, two hundred miles of trail separate its plantations
from the Pacific. Twelve days’ hard riding is required to reach Lima
over the old colonial trade route. It is three days to Cuzco at the end
of the three-hundred-mile railway from the port of Mollendo. The trails
to the Atlantic rivers are impossible for trading purposes. Deep sunk in
a subtropical valley, the irrigable alluvial land of Abancay tempts the
production of sugar.

But nature offers no easy route out of the valley. For centuries the
product has been exported at almost prohibitive cost, as in the eastern
valley of Santa Ana. The coastal valleys enjoy easy access to the sea.
Each has its own port at the valley mouth, where ocean steamers call for
cargo. Many have short railway lines from port to valley head. The
eastern valleys and Abancay have been clamoring for railways, better
trails, and wagon roads. From the public fund they get what is left. The
realization of their hopes has been delayed too long. It would be both
economic and military strategy to give them the desired railway.
Revolutions in Peru always start in one of two ways: either by a _coup_
at Lima or an unchecked uprising in an interior province. Bolivia has
shown the way out of this difficulty. Two of her four large centers--La
Paz and Oruro--are connected by rail, and the line to Cochabamba lacks
only a few kilometres of construction.[16] To Sucre a line has been long
projected. Formerly a revolution at one of the four towns was
exceedingly difficult to stamp out. Diaz had the same double motive in
encouraging railway building in the remote desert provinces of Northern
Mexico, where nine out of ten Mexican revolutions gather headway.
Argentina has enjoyed a high degree of political unity since her railway
system was extended to Córdoba and Tucumán. The last uprising, that of
1906, took place on her remotest northeastern frontier.

We had ample opportunity to see the hatred of the rebels. At nightfall
of September 25th we rode into the courtyard of Hacienda Auquibamba. We
had traveled under the worst possible circumstances. Our mules had been
enfeebled by hot valley work at Santa Ana and the lower Urubamba and the
cold mountain climate of the Cordillera Vilcapampa. The climb out of the
Apurimac canyon, even without packs, left them completely exhausted. We
were obliged to abandon one and actually to pull another along. It had
been a hard day in spite of a prolonged noon rest. Everywhere our
letters of introduction had won an outpouring of hospitality among a
people to whom hospitality is one of the strongest of the unwritten laws
of society. Our soldier escort rode ahead of the pack train.

As the clatter of his mules’ hoofs echoed through the dark buildings the
manager rushed out, struck a light and demanded “Who’s there?” To the
soldier’s cheerful “Buena noche, Señor,” he sneeringly replied “Halto!
Guardia de la República, aqui hay nada para un soldado del gobierno.”
Whereupon the soldier turned back to me and said we should not be able
to stop here, and coming nearer me he whispered “He is a revolutionary.”
I dismounted and approached the haughty manager, who was in a really
terrible mood. Almost before I could begin to ask him for accommodations
he rattled off that there was no pasture for our beasts, no food for us,
and that we had better go on to the next hacienda. “Absolutamente nada!”
he repeated over and over again, and at first I thought him drunk. Since
it was then quite dark, with no moon, but instead heavy black clouds
over the southern half of the sky and a brisk valley wind threatening
rain, I mildly protested that we needed nothing more than shelter. Our
food boxes would supply our wants, and our mules, even without fodder,
could reach Abancay the next day. Still he stormed at the government and
would have none of us. I reminded him that his fields were filled with
sugar cane and that it was the staple forage for beasts during the part
of the year when pasture was scarce. The cane was too valuable, he said.
It was impossible to supply us. I was on the point of pitching camp
beside the trail, for it was impossible to reach the next hacienda with
an exhausted outfit.

Just then an older man stepped into the circle of light and amiably
inquired the purpose of our journey. When it was explained, he turned to
the other and said it was unthinkable that men should be treated so
inhospitably in a strange land. Though he himself was a guest he urged
that the host should remember the laws of hospitality, whereupon the
latter at last grudgingly asked us to join him at his table and to turn
our beasts over to his servants. It was an hour or more before he would
exhibit any interest in us. When he had learned of our object in
visiting Abancay he became somewhat more friendly, though his hostility
still manifested itself. Nowhere else in South America have I seen
exhibited such boorish conduct. Nevertheless the next morning I noticed
that our mules had been well fed. He said good-by to us as if he were
glad to be rid of any one in any way connected with the hostile
government. Likewise the manager at Hacienda Pasaje held out almost
until the last before he would consent to aid us with fresh beasts.
Finally, after a day of courting I gave him a camp chair. He was so
pleased that he not only gave us beasts, but also a letter of
introduction to one of his caretakers on a farm at the top of the
cuesta. Here on a cold, stormy night we found food and fuel and the
shelter of a friendly roof.

A by-product of the revolution, as of all revolutions in thinly settled
frontier regions, was the organization of small bands of outlaws who
infested the lonely trails, stole beasts, and left their owners robbed
and helpless far from settlements. We were cautioned to beware of them,
both by Señor Gonzales, the Prefect at Abancay, and by the Subprefect of
Antabamba. Since some of the bandits had been jailed, I could not doubt
the accuracy of the reports, but I did doubt stories of murder and of
raids by large companies of mountain bandits. As a matter of fact we
were robbed by the Governor of Antabamba, but in a way that did not
enable us to find redress in either law or lead. The story is worth
telling because it illustrates two important facts: first, the vile
so-called government that exists in some places in the really remote
sections of South America, and second, the character of the mountain
Indians.

The urgent letter from the Prefect of Abancay to the Subprefect of
Antabamba quickly brought the latter from his distant home. When we
arrived we found him drinking with the Governor. The Subprefect was most
courteous. The Governor was good-natured, but his face exhibited a rare
combination of cruelty and vice. We were offered quarters in the
municipal building for the day or two that we were obliged to stop in
the town. The delay enabled us to study the valley to which particular
interest attaches because of its situation in the mountain zone between
the lofty pastures of the Alpine country and the irrigated fields of the
valley farmers.

Antabamba itself lies on a smooth, high-level shoulder of the youthful
Antabamba Valley. The valley floor is narrow and rocky, and affords
little cultivable land. On the valley sides are steep descents and
narrow benches, chiefly structural in origin, over which there is
scattered a growth of scrub, sufficient to screen the deer and the bear,
and, more rarely, vagrant bands of vicuña that stray down from their
accustomed haunts in the lofty Cordillera. Three thousand feet above the
valley floor a broad shoulder begins (Fig. 60) and slopes gently up to
the bases of the true mountains that surmount the broad rolling summit
platform. Here are the great pasture lands of the Andes and their
semi-nomadic shepherds. The highest habitation in the world is located
here at 17,100 feet (5,210 m.), near a secondary pass only a few miles
from the main axis of the western chain, and but 300 feet (91 m.) below
it.

The people of Antabamba are both shepherds and farmers. The elevation is
12,000 feet (3,658 m.), too high and exposed for anything more than
potatoes. Here is an Indian population pure-blooded, and in other
respects, too, but little altered from its original condition. There is
almost no communication with the outside world. A deep canyon fronts the
town and a lofty mountain range forms the background.

At nightfall, one after another, the Indians came in from the field and
doffed their caps as they passed our door. Finally came the “Teniente
Gobernador,” or Lieutenant Governor. He had only a slight strain of
white blood. His bearing was that of a sneak, and he confirmed this
impression by his frank disdain for his full-blooded townsmen. “How
ragged and ugly they are! You people must find them very stupid,” etc.
When he found that we had little interest in his remarks, he asked us if
we had ever seen Lima. We replied that we had, whereupon he said, “Do
you see the gilded cross above the church yonder? I brought that on
muleback all the way from Lima! Think of it! These ignorant people have
never seen Lima!” His whole manner as he drew himself up and hit his
breast was intended to make us think that he was vastly superior to his
neighbors. The sequel shows that our first estimate of him was correct.

We made our arrangements with the Governor and departed. To inspire
confidence, and at the Governor’s urgent request, we had paid in advance
for our four Indians and our fresh beasts--and at double the usual
rates, for it was still winter in the Cordillera. They were to stay with
us until we reached Cotahuasi, in the next Department beyond the
continental divide, where a fresh outfit could be secured. The
Lieutenant Governor accompanied us to keep the party together. They
appeared to need it. Like our Indian peons at Lambrama the week before,
these had been taken from the village jail and represented the scum of
the town. As usual they behaved well the first day. On the second night
we reached the Alpine country where the vegetation is very scanty and
camped at the only spot that offered fuel and water. The elevation was
16,000, and here we had the lowest temperature of the whole journey, +6°
F. (-14.4° C.). Ice covered the brook near camp as soon as the sun went
down and all night long the wind blew down from the lofty Cordillera
above us, bringing flurries of snow and tormenting our unprotected
beasts. It seemed to me doubtful if our Indians would remain. I
discussed with the other members of the party the desirability of
chaining the peons to the tent pole, but this appeared so extreme a
measure that we abandoned the idea after warning the Teniente that he
must not let them escape.

At daybreak I was alarmed at the unusual stillness about camp. A glance
showed that half our hobbled beasts had drifted back toward Antabamba
and no doubt were now miles away. The four Indian peons had left also,
and their tracks, half buried by the last snowfall, showed that they had
left hours before and that it was useless to try to overtake them.
Furthermore we were making a topographic map across the Cordillera, and,
in view of the likelihood of snow blockading the 17,600-foot (5,360 m.)
pass which we had to cross, the work ought not to be delayed. With all
these disturbing conditions to meet, and suffering acutely from mountain
sickness, I could scarcely be expected to deal gently with our official.
I drew out the sleeping Teniente and set him on his feet. To my inquiry
as to the whereabouts of the Indians that he had promised to guard, he
blinked uncertainly, and after a stupid “Quien sabe?” peered under the
cover of a sheepskin near by as if the peons had been transformed into
insects and had taken refuge under a blade of grass. I ordered him to
get breakfast and after that to take upon his back the instruments that
two men had carried up to that time, and accompany the topographer. Thus
loaded, the Lieutenant Governor of Antabamba set out on foot a little
ahead of the party. Hendriksen, the topographer, directed him to a
17,000-foot peak near camp, one of the highest stations occupied in the
traverse. When the topographer reached the summit the instruments were
there but the Teniente had fled. Hendriksen rapidly followed the tracks
down over the steep snow-covered wall of a deeply recessed cirque, but
after a half-hour’s search could not get sight of the runaway, whereupon
he returned to his station and took his observations, reaching camp in
the early afternoon.

In the meantime I had intercepted two Indians who had come from
Cotahuasi driving a llama train loaded with corn. They held a long
conversation at the top of the pass above camp and at first edged
suspiciously away. But the rough ground turned them back into the trail
and at last they came timidly along. They pretended not to understand
Spanish and protested vigorously that they had to keep on with their
llamas. I thought from the belligerent attitude of the older, which grew
rapidly more threatening as he saw that I was alone, that I was in for
trouble, but when I drew my revolver he quickly obeyed the order to sit
down to breakfast, which consisted of soup, meat, and army biscuits. I
also gave them coca and cigarettes, the two most desirable gifts one can
make to a plateau Indian, and thereupon I thought I had gained their
friendship, for they at last talked with me in broken Spanish. The older
one now explained that he must at all hazards reach Matará by nightfall,
but he would be glad to leave his son to help us. I agreed, and he set
out forthwith. The _arriero_ (muleteer) had now returned with the lost
mules and with the assistance of the Indian we soon struck camp and
loaded our mules. I cautioned the arriero to keep close watch of the
Indian, for at one time I had caught on his face an expression of hatred
more intense than I had ever seen before. The plateau Indian of South
America is usually so stupid and docile that the unexpectedly venomous
look of the man after our friendly conversation and my good treatment
alarmed me. At the last moment, and when our backs were turned, our
Indian, under the screen of the packs, slipped away from us. The arriero
called out to know where he had gone. It took us but a few moments to
gain the top of a hill that commanded the valley. Fully a half-mile away
and almost indistinguishable against the brown of the valley floor was
our late assistant, running like a deer. No mule could follow over that
broken ground at an elevation of 16,000 feet, and so he escaped.

Fortunately that afternoon we passed a half-grown boy riding back toward
Antabamba and he promised to hand the Governor a note in Spanish,
penciled on a leaf of my traverse book. I dropped all the polite phrases
that are usually employed and wrote as follows:

“Señor Gobernador:

“Your Indians have escaped, likewise the Lieutenant Governor. They
have taken two beasts. In the name of the Prefect of Abancay, I ask
you immediately to bring a fresh supply of men and animals. We
shall encamp near the first pass, three days west of Antabamba,
until you come.”

We were now without Indians to carry the instruments, which had
therefore to be strapped to the mules. Without guides we started
westward along the trail. At the next pass the topographer rode to the
summit of a bluff and asked which of the two trails I intended to
follow. Just then a solitary Indian passed and I shouted back that I
would engage the Indian and precede the party, and he could tell from my
course at the fork of the trail how to direct his map and where to gain
camp at nightfall. But the Indian refused to go with us. All my
threatening was useless and I had to force myself to beat him into
submission with my quirt. Several repetitions on the way, when he
stubbornly refused to go further, kept our guide with us until we
reached a camp site. I had offered him a week’s pay for two hours’ work,
and had put coca and cigarettes into his hands. When these failed I had
to resort to force. Now that he was about to leave I gave him double the
amount I had promised him. He could scarcely believe his eyes. He rushed
up to the side of my mule, and reaching around my waist embraced me and
thanked me again and again. The plateau Indian is so often waylaid in
the mountains and impressed for service, then turned loose without pay
or actually robbed, that a _promise_ to pay holds no attraction for him.
I had up to the last moment resembled this class of white. He was
astonished to find that I really meant to pay him well.

Then he set out upon the return, faithfully delivering my note to the
topographer about the course of the trail and the position of the camp.
He had twelve miles to go to the first mountain hut, so that he could
not have traveled less than that distance to reach shelter. The next
morning a mantle of snow covered everything, yet when I pushed back the
tent flap there stood my scantily clad Indian of the night before,
shivering, with sandaled feet in the snow, saying that he had come back
to work for me!

This camp was number thirteen out of Abancay, and here our topographer
was laid up for three days. Heretofore the elevation had had no effect
upon him, but the excessively lofty stations of the past few days and
the hard climbing had finally prostrated him. We had decided to carry
him out by the fourth day if he felt no better, but happily he recovered
sufficiently to continue the work. The delay enabled the Governor to
overtake us with a fresh outfit. On the morning of our third day in
camp he overtook us with a small escort of soldiers accompanied by the
fugitive Teniente. He said that he had come to arrest me on the charge
of maltreating an official of Peru. A few packages of cigarettes and a
handful of raisins and biscuits so stirred his gratitude that we parted
the best of friends. Moreover he provided us with four fresh beasts and
four new men, and thus equipped we set out for a rendezvous about ten
miles away. But the faithless Governor turned off the trail and sought
shelter at the huts of a company of mountain shepherds. That night his
men slept on the ground in a bitter wind just outside our camp at 17,200
feet. They complained that they had no food. The Governor had promised
to join us with llama meat for the peons. We fed them that night and
also the next day. But we had by that time passed the crest of the
western Cordillera and were outside the province of Antabamba. The next
morning not only our four men but also our four beasts were missing. We
were stranded and sick just under the pass. To add to our distress the
surgeon, Dr. Erving, was obliged to leave us for the return home, taking
the best saddle animal and the strongest pack mule. It was impossible to
go on with the map. That morning I rode alone up a side valley until I
reached a shepherd’s hut, where I could find only a broken-down,
shuffling old mule, perfectly useless for our hard work.

Then there happened a piece of good luck that seems almost providential.
A young man came down the trail with three pack mules loaded with llama
meat. He had come from the Cotahuasi Valley the week before and knew the
trail. I persuaded him to let us hire one of his mules. In this way and
by leaving the instruments and part of our gear in the care of two
Indian youths we managed to get to Cotahuasi for rest and a new outfit.

The young men who took charge of part of our outfit interested me very
greatly. I had never seen elsewhere so independent and clear-eyed a pair
of mountain Indians. At first they would have nothing to do with us.
They refused us permission to store our goods in their hut. To them we
were railroad engineers. They said that the railway might come and when
it did it would depopulate the country. The railway was a curse.
Natives were obliged to work for the company without pay. Their uncle
had told them of frightful abuses over at Cuzco and had warned them not
to help the railway people in any way. They had moved out here in a
remote part of the mountains so that white men could not exploit them.

In the end, however, we got them to understand the nature of our work.
Gifts of various sorts won their friendship, and they consented to guard
the boxes we had to leave behind. Two weeks later, on his return, the
topographer found everything unmolested.

I could not but feel that the spirit of those strong and independent
young men was much better for Peru than the cringing, subservient spirit
of most of the Indians that are serfs of the whites. The policy of the
whites has been to suppress and exploit the natives, to abuse them, and
to break their spirit. They say that it keeps down revolution; it keeps
the Indian in his place. But certainly in other respects it is bad for
the Indian and it is worse for the whites. Their brutality toward the
natives is incredible. It is not so much the white himself as the
vicious half-breed who is often allied with him as his agent.

I shall never forget the terror of two young girls driving a donkey
before them when they came suddenly face to face with our party, and we
at the same time hastily scrambled off our beasts to get a photograph of
a magnificent view disclosed at the bend of the steep trail. They
thought we had dismounted to attack them, and fled screaming in abject
fear up the mountain side, abandoning the donkey and the pack of
potatoes which must have represented a large part of the season’s
product. It is a kind of highway robbery condoned because it is only
robbing an Indian. He is considered to be lawful prey. His complaint
goes unnoticed. In the past a revolution has offered him sporadic
chances to wreak vengeance. More often it adds to his troubles by
scattering through the mountain valleys the desperate refugees or
lawless bands of marauders who kill the flocks of the mountain shepherds
and despoil their women.

There are still considerable numbers of Indians who shun the white man
and live in the most remote corners of the mountains. I have now and
again come upon the most isolated huts, invisible from the valley
trails. They were thatched with grass; the walls were of stone; the
rafters though light must have required prodigious toil, for all timber
stops at 12,000 feet on the mountain borders. The shy fugitive who
perches his hut near the lip of a hanging valley far above the trail may
look down himself unseen as an eagle from its nest. When the owner
leaves on a journey, or to take his flock to new pastures, he buries his
pottery or hides it in almost inaccessible caves. He locks the door or
bars it, thankful if the spoiler spares rafters and thatch.

At length we reached Cotahuasi, a town sprawled out on a terrace just
above the floor of a deep canyon (Fig. 29). Its flower gardens and
pastures are watered by a multitude of branching canals lined with low
willows. Its bright fields stretch up the lower slopes and alluvial fans
of the canyon to the limits of irrigation where the desert begins. The
fame of this charming oasis is widespread. The people of Antabamba and
Lambrama and even the officials of Abancay spoke of Cotahuasi as
practically the end of our journey. Fruits ripen and flowers blossom
every month of the year. Where we first reached the canyon floor near
Huaynacotas, elevation 11,500 feet (3,500 m.), there seemed to be acres
of rose bushes. Only the day before at an elevation of 16,800 feet
(5,120 m.) we had broken thick ice out of a mountain spring in order to
get water; now we were wading a shallow river, and grateful for the
shade along its banks. Thus we came to the town prepared to find the
people far above their plateau neighbors in character. Yet, in spite of
friendly priests and officials and courteous shopkeepers, there was a
spirit strangely out of harmony with the pleasant landscape.

Inquiries showed that even here, where it seemed that only sylvan peace
should reign, there had recently been let loose the spirit of barbarism.
We shall turn to some of its manifestations and look at the reasons
therefor.

In the revolution of 1911 a mob of drunken, riotous citizens gathered to
storm the Cotahuasi barracks and the jail. A full-blooded Indian
soldier, on duty at the entrance, ordered the rioters to stop and when
they paid no heed he shot the leader and scattered the crowd. The
captain thereupon ordered the soldier to Arequipa because his life was
no longer safe outside the barracks. A few months later he was assigned
to Professor Bingham’s Coropuna expedition. Professor Bingham reached
the Cotahuasi Valley as I was about to leave it for the coast, and the
soldier was turned over to me so that he might leave Cotahuasi at the
earliest possible moment, for his enemies were plotting to kill him.

He did not sleep at all the last night of his stay and had us called at
three in the morning. He told his friends that he was going to leave
with us, but that they were to announce his leaving a day later. In
addition, the Subprefect was to accompany us until daybreak so that no
harm might befall me while under the protection of a soldier who
expected to be shot from ambush.

At four o’clock our whispered arrangements were made, we opened the
gates noiselessly, and our small cavalcade hurried through the
pitch-black streets of the town. The soldier rode ahead, his rifle
across his saddle, and directly behind him rode the Subprefect and
myself. The pack mules were in the rear. We had almost reached the end
of the street when a door opened suddenly and a shower of sparks flew
out ahead of us. Instantly the soldier struck spurs into his mule and
turned into a side street. The Subprefect drew his horse back savagely
and when the next shower of sparks flew out pushed me against the wall
and whispered: “Por Dios, quien es?” Then suddenly he shouted: “Sopla no
mas, sopla no mas” (stop blowing).

Thereupon a shabby penitent man came to the door holding in his hand a
large tailor’s flatiron. The base of it was filled with glowing charcoal
and he was about to start his day’s work. The sparks were made in the
process of blowing through the iron to start the smoldering coals. We
greeted him with more than ordinary friendliness and passed on.

At daybreak we had reached the steep western wall of the canyon where
the real ascent begins, and here the Subprefect turned back with many
_felicidades_ for the journey and threats for the soldier if he did not
look carefully after the pack train. From every angle of the zigzag
trail that climbs the “cuesta” the soldier scanned the valley road and
the trail below him. He was anxious lest news of his escape reach his
enemies who had vowed to take his life. Half the day he rode turned in
his saddle so as to see every traveler long before he was within harm’s
reach. By nightfall we safely reached Salamanca, fifty miles away (Fig.
62).

The alertness of the soldier was unusual and I quite enjoyed his close
attention to the beasts and his total abstinence, for an alert and sober
soldier on detail is a rare phenomenon in the interior of Peru. But all
Salamanca was drunk when we arrived--Governor, alcaldes, citizens. Even
the peons drank up in brandy the money that we gave them for forage and
let the beasts starve. The only sober person I saw was the white
telegraph operator from Lima. He said that he had to stay sober, for the
telegraph office--the outward sign of government--was the special object
of attack of every drink-crazed gang of rioters. They had tried to break
in a few nights before and he had fired his revolver point-blank through
the door. The town offered no shelter but the dark filthy hut of the
Gobernador and the tiny telegraph office. So I made up my bed beside
that of the operator. We shared our meals and chatted until a late hour,
he recounting the glories of Lima, to which he hoped to return at the
earliest possible moment, and cursing the squalid town of Salamanca. His
operator’s keys were old, the batteries feeble, and he was in continual
anxiety lest a message could not be received. In the night he sprang out
of bed shouting frantically:

“Estan llamando” (they are calling), only to stumble over my bed and
awaken himself and offer apologies for walking in his sleep.

Meanwhile my soldier, having regained his courage, began drinking. It
was with great difficulty that I got started, after a day’s delay, on
the trail to Chuquibamba. There his thirst quite overcame him. To
separate him from temptation it became necessary to lock him up in the
village jail. This I did repeatedly on the way to Mollendo, except
beyond Quilca, where we slept in the hot marshy valley out of reach of
drink, and where the mosquitoes kept us so busy that either eating or
drinking was almost out of the question.

The drunken rioters of Cotahuasi and their debauched brothers at
Salamanca are chiefly natives of pure or nearly pure Indian blood. They
are a part of the great plateau population of the Peruvian Andes. Have
they degenerated to their present low state, or do they display merely
the normal condition of the plateau people? Why are they so troublesome
an element? To this as to so many questions that arise concerning the
highland population we find our answer not chiefly in government, or
religion, or inherited character, but in geography. I doubt very much if
a greater relative difference would be seen if two groups of whites were
set down, the one in the cold terrace lands of Salamanca, the other in
the warm vineyards of Aplao, in the Majes Valley. The common people of
these two towns were originally of the same race, but the lower valley
now has a white element including even most of those having the rank of
peons. Greater differences in character could scarcely be found between
the Aztecs and the Iroquois. In the warm valley there is of coarse
drunkenness, but it is far from general; there is stupidity, but the
people are as a whole alert; and finally, the climate and soil produce
grapes from which famous wines are made, they produce sugar cane,
cotton, and alfalfa, so that the whites have come in, diluted the Indian
blood, and raised the standard of life and behavior. Undoubtedly their
influence would tend to have the same general effect if they mixed in
equal numbers with the plateau groups. There is, however, a good reason
for their not doing so.

[Illustration: FIG. 62--Salamanca, on the floor of the deep Arma Valley
(a tributary of one of the major coast valleys, the Ocoña), which is
really a canyon above this point and which, in spite of its steepness,
is thoroughly terraced and intensively cultivated up to the frost line.]

[Illustration: FIG. 60--View across the Antabamba canyon just above
Huadquirca.]

[Illustration: FIG. 61--Huancarama, west of Abancay, on the famous Lima
to Buenos Aires road. Note the smooth slopes in the foreground. See
Chapter XI.]

The lofty towns of the plateau have a really wretched climate. White men
cannot live comfortably at Antabamba and Salamanca. Further, they are so
isolated that the modest comforts and the smallest luxuries of
civilization are very expensive. To pay for them requires a profitable
industry managed on a large scale and there is no such industry in the
higher valleys. The white who goes there must be satisfied to live like
an Indian. The result is easy to forecast. Outside of government
officers, only the dissolute or unsuccessful whites live in the worst
towns, like Salamanca and Antabamba. A larger valley with a slightly
milder climate and more accessible situation, like Chuquibamba, will
draw a still better grade of white citizen and in the largest of
all--Cuzco and the Titicaca basin--we find normal whites in larger
numbers, though they nowhere live in such high ratios to the Indian as
on the coast and in the lower valleys near the coast. With few
exceptions the white population of Peru is distributed in response to
favorable combinations of climate, soil, accessibility, and general
opportunities to secure a living without extreme sacrifice.

These facts are stated in a simple way, for I wish to emphasize the
statement that the Indian population responds to quite other stimuli.
Most of the luxuries and comforts of the whites mean nothing to the
Indian. The machine-made woolens of the importers will probably never
displace his homespun llama-wool clothing. His implements are few in
number and simple in form. His tastes in food are satisfied by the few
products of his fields and his mountain flocks. Thus he has lived for
centuries and is quite content to live today. Only coca and brandy tempt
him to engage in commerce, to toil now and then in the hot valleys, and
to strive for more than the bare necessities of life. Therefore it
matters very little to him if his home town is isolated, or the
resources support but a small group of people. He is so accustomed to a
solitary existence in his ramblings with his flocks that a village of
fifty houses offers social enjoyments of a high order. Where a white
perishes for lack of society the Indian finds himself contented.
Finally, he is not subject to the white man’s exploitation when he lives
in remote places. The pastures are extensive and free. The high valley
lands are apportioned by the alcalde according to ancient custom. His
life is unrestricted by anything but the common law and he need have no
care for the morrow, for the seasons here are almost as fixed as the
stars.

Thus we have a sort of segregation of whites in the lower places where a
modern type of life is maintained and of Indians in the higher places
where they enjoy advantages that do not appeal to the whites. Above
8,000 feet the density of the white population bears a close inverse
proportion to the altitude, excepting in the case of the largest valleys
whose size brings together such numbers as to tempt the commercial and
exploiting whites to live in them. Furthermore, we should find that high
altitude, limited size, and greater isolation are everywhere closely
related to increasing immorality or decreasing character among the
whites. So to the low Indian population there is thus added the lowest
of the white population. Moreover, because it yields the largest
returns, the chief business of these whites is the sale of coca and
brandy and the downright active debauchery of the Indian. This is all
the easier for them because the isolated Indian, like the average
isolated white, has only a low and provincial standard of morality and
gets no help from such stimulation as numbers usually excite.

For example, the Anta basin at harvest time is one of the fairest sights
in Peru. Sturdy laborers are working diligently. Their faces are bright
and happy, their skin clear, their manner eager and animated. They sing
at their work or gather about their mild _chicha_ and drink to the
patron saints of the harvest. The huts are filled with robust children;
all the yards are turned into threshing floors; and from the stubbly
hillslopes the shepherd blows shrill notes upon his barley reeds and
bamboo flute. There is drinking but there is little disorder and there
is always a sober remnant that exercises a restraining influence upon
the group.

In the most remote places of all one may find mountain groups of a high
order of morality unaffected by the white man or actually shunning him.
Clear-eyed, thick-limbed, independent, a fine, sturdy type of man this
highland shepherd may be. But in the town he succumbs to the temptation
of drink. Some writers have tried to make him out a superior to the
plains and low valley type. He is not that. The well-regulated groups of
the lower elevations are far superior intellectually and morally in
spite of the fact that the poorly regulated groups may fall below the
highland dweller in morality. The coca-chewing highlander is a clod.
Surely, as a whole, the mixed breed of the coastal valleys is a far
worthier type, save in a few cases where a Chinese or negroid element or
both have led to local inferiority. And surely, also, that is the worst
combination which results in adding the viciousness of the inferior or
debased white to the stupidity of the highland Indian. It is here that
the effects of geography are most apparent. If the white is tempted in
large numbers because of exceptional position or resources, as at La
Paz, the rule of altitude may have an exception. And other exceptions
there are not due to physical causes, for character is practically never
a question of geography alone. There is the spiritual factor that may
illumine a strong character and through his agency turn a weak community
into a powerful one, or hold a weakened group steadfast against the
forces of disintegration. Exceptions arise from this and other causes
and yet with them all in mind the geographic factor seems predominant in
the types illustrated herewith.[17]

CHAPTER VIII

THE COASTAL DESERT

To the wayfarer from the bleak mountains the warm green valleys of the
coastal desert of Peru seem like the climax of scenic beauty. The
streams are intrenched from 2,000 to 4,000 feet, and the valley walls in
some places drop 500 feet by sheer descents from one level to another.
The cultivated fields on the valley floors look like sunken gardens and
now and then one may catch the distant glint of sunlight on water. The
broad white path that winds through vineyards and cotton-fields, follows
the foot of a cliff, or fills the whole breadth of a gorge is the
waste-strewn, half-dry channel of the river. In some places almost the
whole floor is cultivated from one valley wall to the other. In other
places the fields are restricted to narrow bands between the river and
the impending cliffs of a narrow canyon. Where tributaries enter from
the desert there may be huge banks of mud or broad triangular fans
covered with raw, infertile earth. The picture is generally touched with
color--a yellow, haze-covered horizon on the bare desert above, brown
lava flows suspended on the brink of the valley, gray-brown cliffs, and
greens ranging from the dull shade of algarrobo, olive and fig trees, to
the bright shade of freshly irrigated alfalfa pastures.

After several months’ work on the cold highlands, where we rode almost
daily into hailstorms or wearisome gales, we came at length to the
border of the valley country. It will always seem to me that the weather
and the sky conspired that afternoon to reward us for the months of toil
that lay behind. And certainly there could be no happier place to
receive the reward than on the brink of the lava plateau above
Chuquibamba. There was promise of an extraordinary view in the growing
beauty of the sky, and we hurried our tired beasts forward so that the
valley below might also be included in the picture. The head of the
Majes Valley is a vast hollow bordered by cliffs hundreds of feet high,
and we reached the rim of it only a few minutes before sunset.

[Illustration: FIG. 63--The deep fertile Majes Valley below Cantas.
Compare with Fig. 6 showing the Chili Valley at Arequipa.]

[Illustration: FIG. 64--The Majes Valley, desert coast, western Peru.
The lighter patches on the valley floor are the gravel beds of the river
at high water. Much of the alluvial land is still uncleared.]

I remember that we halted beside a great wooden cross and that our
guide, dismounting, walked up to the foot of it and kissed and embraced
it after the custom of the mountain folk when they reach the head of a
steep “cuesta.” Also that the trail seemed to drop off like a stairway,
which indeed it was.[18] Everything else about me was completely
overshadowed by snowy mountains, colored sky, and golden-yellow desert.
One could almost forget the dark clouds that gather around the great
mass of Coropuna and the bitter winds that creep down from its glaciers
at night--it seemed so friendly and noble. Behind it lay bulky masses of
rose-tinted clouds. We had admired their gay colors only a few minutes,
when the sun dropped behind the crest of the Coast Range and the last of
the sunlight played upon the sky. It fell with such marvelously swift
changes of color upon the outermost zone of clouds as these were shifted
with the wind that the eye had scarcely time to comprehend a tint before
it was gone and one more beautiful still had taken its place. The
reflected sunlight lay warm and soft upon the white peaks of Coropuna,
and a little later the Alpine glow came out delicately clear.

When we turned from this brilliant scene to the deep valley, we found
that it had already become so dark that its greens had turned to black,
and the valley walls, now in deep shadow, had lost half their splendor.
The color had not left the sky before the lights of Chuquibamba began to
show, and candles twinkled from the doors of a group of huts close under
the cliff. We were not long in starting the descent. Here at last were
friendly habitations and happy people. I had worked for six weeks
between 12,000 and 17,000 feet, constantly ill from mountain sickness,
and it was with no regret that I at last left the plateau and got down
to comfortable altitudes. It seemed good news when the guide told me
that there were mosquitoes in the marshes of Camaná. Any low, hot land
would have seemed like a health resort. I had been in the high country
so long that, like the Bolivian mining engineer, I wanted to get down
not only to sea level, but below it!

[Illustration: FIG. 65--Regional diagram to show the physical relations
in the coastal desert of Peru. For location, see Fig. 20.]

If the reader will examine Figs. 65 and 66, and the photographs that
accompany them, he may gain an idea of the more important features of
the coastal region. We have already described, in Chapters V and VII,
the character of the plateau region and its people. Therefore, we need
say little in this place of the part of the Maritime Cordillera that is
included in the figure. Its unpopulated rim (see p. 54), the
semi-nomadic herdsmen and shepherds from Chuquibamba that scour its
pastures in the moist vales about Coropuna, and the gnarled and stunted
trees at 13,000 feet (3,960 m.) which partly supply Chuquibamba with
firewood, are its most important features. A few groups of huts just
under the snowline are inhabited for only a part of the year. The
delightful valleys are too near and tempting. Even a plateau Indian
responds to the call of a dry valley, however he may shun the moist,
warm valleys on the eastern border of the Cordillera.

[Illustration: FIG. 66--Irrigated and irrigable land of the coastal belt
of Peru. The map exhibits in a striking manner how small a part of the
whole Pacific slope is available for cultivation. Pasture grows over all
but the steepest and the highest portions of the Cordillera to the right
of (above) the dotted line. Another belt of pasture too narrow to show
on the map, grows in the fog belt on the seaward slopes of the Coast
Range. Scale, 170 miles to the inch.]

The greater part of the coastal region is occupied by the desert. Its
outer border is the low, dry, gentle, eastward-facing slope of the Coast
Range. Its inner border is the foot of the steep descent that marks the
edge of the lava plateau. This descent is a fairly well-marked line,
here and there broken by a venturesome lava flow that extends far out
from the main plateau. Within these definite borders the desert extends
continuously northwestward for hundreds of miles along the coast of Peru
from far beyond the Chilean frontier almost to the border of Ecuador. It
is broken up by deep transverse valleys and canyons into so-called
“pampas,” each of which has a separate name; thus west of Arequipa
between the Vitor and Majes valleys are the “Pampa de Vitor” and the
“Pampa de Sihuas,” and south of the Vitor is the “Pampa de Islay.”

The pampa surfaces are inclined in general toward the sea. They were
built up to their present level chiefly by mountain streams before the
present deep valleys were cut, that is to say, when the land was more
than a half-mile lower. Some of their material is wind-blown and on the
walls of the valleys are alternating belts of wind-blown and water-laid
strata from one hundred to four hundred feet thick as if in past ages
long dry and long wet periods had succeeded each other. The wind has
blown sand and dust from the desert down into the valleys, but its chief
work has been to drive the lighter desert waste up partly into the
mountains and along their margins, partly so high as to carry it into
the realm of the lofty terrestrial winds, whence it falls upon surfaces
far distant from the fields of origin. There are left behind the heavier
sand which the wind rolls along on the surfaces and builds into
crescentic dunes called médanos, and the pebbles that it can sandpaper
but cannot remove bodily. Thus there are belts of dunes, belts of
irregular sand drifts, and belts of true desert “pavement” (a residual
mantle of faceted pebbles and irregular stones).

[Illustration: THE YALE PERUVIAN EXPEDITION OF 1911

HIRAM BINGHAM, DIRECTOR

CAMANÁ QUADRANGLE

(_Aplao_)]

Yet another feature of the desert pampa are the “dry” valleys that join
the through-flowing streams at irregular intervals, as shown in the
accompanying regional diagram. If one follow a dry valley to its head
he will find there a set of broad and shallow tributaries. Sand drifts
may clog them and appear to indicate that water no longer flows through
them. They are often referred to by unscientific travelers as evidences
of a recent change of climate. I had once the unusual opportunity (in
the mountains of Chile) of seeing freshly fallen snow melted rapidly and
thus turned suddenly into the streams. In 1911 this happened also at San
Pedro de Atacama, northern Chile, right in the desert at 8,000 feet
(2,440 m.) elevation, and in both places the dry, sand-choked valleys
were cleaned out and definite channels reëstablished. From a large
number of facts like these we know that the dry valleys represent the
work of the infrequent rains. No desert is absolutely rainless, although
until recently it was the fashion to say so. Naturally the wind, which
works incessantly, partly offsets the work of the water. Yet the wind
can make but little impression upon the general outlines of the dry
valleys. They remain under the dominance of the irregular rains. These
come sometimes at intervals of three or four years, again at intervals
of ten to fifteen years, and some parts of the desert have probably been
rainless for a hundred years. Some specific cases are discussed in the
chapter on Climate.

The large valleys of the desert zone have been cut by snow-fed streams
and then partly filled again so that deep waste lies on their floors and
abuts with remarkable sharpness against the bordering cliffs (Fig. 155).
Extensive flats are thus available for easy cultivation, and the
through-flowing streams furnish abundant water to the irrigating canals.
The alluvial floor begins almost at the foot of the steep western slope
of the lava plateau, but it is there stony and coarse--hence
Chuquibamba, or plain of stones (chuqui = stone; bamba = plain). Farther
down and about half-way between Chuquibamba and Aplao (Camaná
Quadrangle) it is partly covered with fresh mud and sand flows from the
bordering valley walls and the stream is intrenched two hundred feet. A
few miles above Aplao the stream emerges from its narrow gorge and
thenceforth flows on the surface of the alluvium right to the sea.
Narrow places occur between Cantas and Aplao, where there is a
projection of old and hard quartzitic rock, and again above Camaná,
where the stream cuts straight across the granite axis of the Coast
Range. Elsewhere the rock is either a softer sandstone or still
unindurated sands and gravels, as at the top of the desert series of
strata that are exposed on the valley wall. The changing width of the
valley is thus a reflection of the changing hardness of the rock.

There is a wide range of products between Chuquibamba at 10,000 feet
(3,050 m.) at the head of the valley and Camaná near the valley mouth.
At the higher levels fruit will not grow--only alfalfa, potatoes, and
barley. A thousand feet below Chuquibamba fruit trees appear. Then
follows a barren stretch where there are mud flows and where the river
is intrenched. Below this there is a wonderful change in climate and
products. The elevation falls off 4,000 feet and the first cultivated
patches below the middle unfavorable section are covered with grape
vines. Here at 3,000 feet (900 m.) elevation above the sea begin the
famous vineyards of the Majes Valley, which support a wine industry that
dates back to the sixteenth century. Some of the huge buried earthenware
jars for curing the wine at Hacienda Cantas were made in the reign of
Philip II.

The people of Aplao and Camaná are among the most hospitable and
energetic in Peru, as if these qualities were but the reflection of the
bounty of nature. Nowhere could I see evidences of crowding or of the
degeneracy or poverty that is so often associated with desert people.
Water is always plentiful; sometimes indeed too plentiful, for floods
and changes in the bed of the river are responsible for the loss of a
good deal of land. This abundance of water means that both the small and
the large landowners receive enough. There are none of the troublesome
official regulations, as in the poorer valleys with their inevitable
favoritism or downright graft. Yet even here the valley is not fully
occupied; at many places more land could be put under cultivation. The
Belaunde brothers at Cantas have illustrated this in their new cotton
plantation, where clearings and new canals have turned into cultivated
fields tracts long covered with brush.

The Majes Valley sorely lacks an adequate port. Its cotton, sugar, and
wine must now be shipped to Camaná and thence to Mollendo, either by a
small bi-weekly boat, or by pack-train over the coast trail to Quilca,
where ocean steamers call. This is so roundabout a way that the planters
of the mid-valley section and the farmers of the valley head now export
their products over the desert trail from Cantas to Vitor on the
Mollendo-Arequipa railroad, whence they can be sent either to the cotton
mills or the stores of Arequipa, the chief distributing market of
southern Peru, or to the ocean port.

The foreshore at Camaná is low and marshy where the salt water covers
the outer edge of the delta. In the hollow between two headlands a broad
alluvial plain has been formed, through which the shallow river now
discharges. Hence the natural indentation has been filled up and the
river shoaled. To these disadvantages must be added a third, the
shoaling of the sea bottom, which compels ships to anchor far off shore.
Such shoals are so rare on this dry and almost riverless coast as to be
a menace to navigation. The steamer _Tucapelle_, like all west-coast
boats, was sailing close to the unlighted shore on a very dark night in
April, 1911, when the usual fog came on. She struck the reef just off
Camaná. Half of her passengers perished in trying to get through the
tremendous surf that broke over the bar. The most practicable scheme for
the development of the port would seem to be a floating dock and tower
anchored out of reach of the surf, and connected by cable with a railway
on shore. Harbor works would be extraordinarily expensive. The valley
can support only a modest project.

The relations of Fig. 65, representing the Camaná-Vitor region, are
typical of southern Peru, with one exception. In a few valleys the
streams are so small that but little water is ever found beyond the foot
of the mountains, as at Moquegua. In the Chili Valley is Arequipa (8,000
feet), right at the foot of the big cones of the Maritime Cordillera
(see Fig. 6). The green valley floor narrows rapidly and cultivation
disappears but a few miles below the town. Outside the big valleys
cultivation is limited to the best spots along the foot of the Coast
Range, where tiny streams or small springs derive water from the zone of
clouds and fogs on the seaward slopes of the Coast Range. Here and there
are olive groves, a vegetable garden, or a narrow alfalfa meadow,
watered by uncertain springs that issue below the hollows of the
bordering mountains.

[Illustration: FIG. 67--Irrigated and irrigable land in the Ica Valley
of the coastal desert of Peru.]

[Illustration: FIG. 68--The projected canal to convey water from the
Atlantic slope to the Pacific slope of the Maritime Cordillera.[19]]

In central and northern Peru the coastal region has aspects quite
different from those about Camaná. At some places, for example north of
Cerro Azul, the main spurs of the Cordillera extend down to the shore.
There is neither a low Coast Range nor a broad desert pampa. In such
places flat land is found only on the alluvial fans and deltas. Lima and
Callao are typical. Fig. 66, compiled from Adams’s reports on the water
resources of the coastal region of Peru, shows this distinctive feature
of the central region. Beyond Salaverry extends the northern region,
where nearly all the irrigated land is found some distance back from the
shore. The farther north we go the more marked is this feature, because
the coastal belt widens. Catacaos is several miles from the sea, and
Piura is an interior place. At the extreme north, where the rains begin,
as at Tumbez, the cultivated land once more extends to the coast.

[Illustration: FIG. 69--A stream of the intermittent type in the coastal
desert of Peru. Depth of water in the Puira River at Puira, 1905. (Bol.
de Minas del Perú, 1906, No. 45, p. 2.)]

[Illustration: FIG. 70--A stream of the perennial type in the coastal
desert of Peru. Depth of water in the Chira River at Sullana, 1905. Data
from May to September are approximate. (Bol. de Minas del Perú, 1906,
No. 45, p. 2.)]

These three regions contain all the fertile coastal valleys of Peru. The
larger ones are impressive--with cities, railways, ports, and land in a
high state of cultivation. But they are after all only a few hundred
square miles in extent. They contain less than a quarter of the people.
The whole Pacific slope from the crest of the Cordillera has about
15,000 square miles (38,850 sq. km.), and of this only three per cent is
irrigated valley land, as shown in Fig. 66. Moreover, only a small
additional amount may be irrigated, perhaps one half of one per cent.
Even this amount may be added not only by a better use of the water but
also by the diversion of streams and lakes from the Atlantic to the
Pacific. Figs. 67 and 68 represent such a project, in which it is
proposed to carry the water of Lake Choclococha through a canal and
tunnel under the continental divide and so to the head of the Ica
Valley. A little irrigation can be and is carried on by the use of well
water, but this will never be an important source because of the great
depth to the ground water, and the fact that it, too, depends ultimately
upon the limited rains.

The inequality of opportunity in the various valleys of the coastal
region depends in large part also upon inequality of river discharge.
This is dependent chiefly upon the sources of the streams, whether in
snowy peaks of the main Cordillera with fairly constant run-off, or in
the western spurs where summer rains bring periodic high water. A third
type has high water during the time of greatest snow melting, combined
with summer rains, and to this class belongs the Majes Valley with its
sources in the snow-cap of Coropuna. The other two types are illustrated
by the accompanying diagrams for Puira and Chira, the former
intermittent in flow, the latter fairly constant.[20]

[Illustration: THE YALE PERUVIAN EXPEDITION OF 1911

HIRAM BINGHAM DIRECTOR

APLAO QUADRANGLE]

CHAPTER IX

CLIMATOLOGY OF THE PERUVIAN ANDES

CLIMATIC BELTS

The noble proportions of the Peruvian Andes and their position in
tropical latitudes have given them climatic conditions of great
diversity. Moreover, their great breadth and continuously lofty summits
have distributed the various climatic types over spaces sufficiently
ample to affect large and important groups of people. When we add to
this the fact that the topographic types developed on a large scale are
distributed at varying elevations, and that upon them depend to a large
degree the chief characteristics of the soil, another great factor in
human distribution, we are prepared to see that the Peruvian Andes
afford some striking illustrations of combined climatic and topographic
control over man.

The topographic features in their relations to the people have been
discussed in preceding chapters. We shall now examine the corresponding
effects of climate. It goes without saying that the topographic and
climatic controls cannot and need not be kept rigidly apart. Yet it
seems desirable, for all their natural interdependence, to give them
separate treatment, since the physical laws upon which their
explanations depend are of course entirely distinct. Further, there is
an independent group of human responses to detailed climatic features
that have little or no connection with either topography or soil.

The chief climatic belts of Peru run roughly from north to south in the
direction of the main features of the topography. Between 13° and 18°
S., however, the Andes run from northwest to southeast, and in short
stretches nearly west-east, with the result that the climatic belts
likewise trend westward, a condition well illustrated on the
seventy-third meridian. Here are developed important climatic features
not found elsewhere in Peru. The trade winds are greatly modified in
direction and effects; the northward-trending valleys, so deep as to be
secluded from the trades, have floors that are nearly if not quite arid;
a restricted coastal region enjoys a heavier rainfall; and the snowline
is much more strongly canted from west to east than anywhere else in the
long belt of mountains from Patagonia to Venezuela. These exceptional
features depend, however, upon precisely the same physical laws as the
normal climatic features of the Peruvian Andes. They can, therefore, be
more easily understood after attention has been given to the larger
aspects of the climatic problem of which they form a part.

The critical relations of trade winds, lofty mountains, and ocean
currents that give distinction to Peruvian climate are shown in Figs. 71
to 73. From them and Fig. 74 it is clear that the two sides of the
Peruvian mountains are in sharp contrast climatically. The eastern
slopes have almost daily rains, even in the dry season, and are clothed
with forest. The western leeward slopes are so dry that at 8,000 feet
even the most drought-resisting grasses stop--only low shrubs live below
this level, and over large areas there is no vegetation whatever. An
exception is the Coast Range, not shown on these small maps, but
exhibited in the succeeding diagram. These have moderate rains on their
seaward (westerly) slopes during some years and grass and shrubby
vegetation grow between the arid coastal terraces below them and the
parched desert above. The greatest variety of climate is enjoyed by the
mountain zone. Its deeper valleys and basins descend to tropical levels;
its higher ranges and peaks are snow-covered. Between are the climates
of half the world compressed, it may be, between 6,000 and 15,000 feet
of elevation and with extremes only a day’s journey apart.

[Illustration: FIG. 71--The three chief topographic regions of Peru.]

[Illustration: FIG. 72--The wind belts of Peru and ocean currents of
adjacent waters.]

[Illustration: FIG. 73--The climatic belts of Peru.]

[Illustration: FIG. 74--Belts of vegetation in Peru.]

In the explanation of these contrasts we have to deal with relatively
simple facts and principles; but the reader who is interested chiefly in
the human aspects of the region should turn to p. 138 where the effects
of the climate on man are set forth. The ascending trades on the eastern
slopes pass successively into atmospheric levels of diminishing
pressure; hence they expand, deriving the required energy for expansion
from the heat of the air itself. The air thereby cooled has a lower
capacity for the retention of water vapor, a function of its
temperature; the colder the air the less water vapor it can take up. As
long as the actual amount of water vapor in the air is less than that
which the air can hold, no rain falls. But the cooling process tends
constantly to bring the warm, moist, ascending air currents to the limit
of their capacity for water vapor by diminishing the temperature.
Eventually the air is saturated and if the capacity diminishes still
further through diminishing temperature some of the water vapor must be
condensed from a gaseous to a liquid form and be dropped as rain.

The air currents that rise thousands of feet per day on the eastern
slopes of the Andes pass again and again through this practically
continuous process and the eastern aspect of the mountains is kept
rain-soaked the whole year round. For the trades here have only the
rarest reversals. Generally they blow from the east day after day and
repeat a fixed or average type of weather peculiar to that part of the
tropics under their steady domination. During the southern summer, when
the day-time temperature contrasts between mountains and plains are
strongest, the force of the trade wind is greatly increased and likewise
the rapidity of the rain-making processes. Hence there is a distinct
seasonal difference in the rainfall--what we call, for want of a better
name, a “wet” and a “dry” season.

On the western or seaward slopes of the Peruvian Andes the trade winds
descend, and the process of rain-making is reversed to one of
rain-taking. The descending air currents are compressed as they reach
lower levels where there are progressively higher atmospheric pressures.
The energy expended in the process is expressed in the air as heat,
whence the descending air gains steadily in temperature and capacity for
water vapor, and therefore is a drying wind. Thus the leeward, western
slopes of the mountains receive little rain and the lowlands on that
side are desert.

THE CLIMATE OF THE COAST

A series of narrow but pronounced climatic zones coincide with the
topographic subdivisions of the western slope of the country between the
crest of the Maritime Cordillera and the Pacific Ocean. This belted
arrangement is diagrammatically shown in Fig. 75. From the zone of lofty
mountains with a well-marked summer rainy season descent is made by
lower slopes with successively less and less precipitation to the desert
strip, where rain is only known at irregular intervals of many years’
duration. Beyond lies the seaward slope of the Coast Range, more or less
constantly enveloped in fog and receiving actual rain every few years,
and below it is the very narrow band of dry coastal terraces.

[Illustration: FIG. 75--Topographic and climatic provinces in the
coastal region of Peru. The broadest division, into the zones of regular
annual rains and of irregular rains, occurs approximately at 8,000 feet
but is locally variable. To the traveler it is always clearly defined by
the change in architecture, particularly of the house roofs. Those of
the coast are flat; those of the sierra are pitched to facilitate run
off.]

The basic cause of the general aridity of the region has already been
noted; the peculiar circumstances giving origin to the variety in detail
can be briefly stated. They depend upon the meteorologic and
hydrographic features of the adjacent portion of the South Pacific Ocean
and upon the local topography.

The lofty Andes interrupt the broad sweep of the southeast trades
passing over the continent from the Atlantic; and the wind circulation
of the Peruvian Coast is governed to a great degree by the high pressure
area of the South Pacific. The prevailing winds blow from the south and
the southeast, roughly paralleling the coast or, as onshore winds,
making a small angle with it. When the Pacific high pressure area is
best developed (during the southern winter), the southerly direction of
the winds is emphasized, a condition clearly shown on the Pilot Charts
of the South Pacific Ocean, issued by the U.S. Hydrographic Office.

[Illustration: FIG. 76--Temperatures at Callao, June-September, 1912,
from observations taken by Captain A. Taylor, of Callao. Air
temperatures are shown by heavy lines; sea temperatures by light lines.
In view of the scant record for comparative land and water temperatures
along the Peruvian coast this record, short as it is, has special
interest.]

The hydrographic feature of greatest importance is the Humboldt Current.
To its cold waters is largely due the remarkably low temperatures of the
coast.[21] In the latitude of Lima its mean surface temperature is about
10° below normal. Lima itself has a mean annual temperature 4.6° F.
below the theoretical value for that latitude, (12° S.). An accompanying
curve shows the low temperature of Callao during the winter months. From
mid-June to mid-September the mean was 61° F., and the annual mean is
only 65.6° F. (18° C.). The reduction in temperature is accompanied by a
reduction in the vapor capacity of the super-incumbent air, an effect of
which much has been made in explanation of the west-coast desert. That
it is a contributing though not exclusive factor is demonstrated in Fig.
77. Curve _A_ represents the hypothetical change of temperature on a
mountainous coast with temporary afternoon onshore winds from a _warm_
sea. Curve _B_ represents the change of temperature if the sea be cold
(actual case of Peru). The more rapid rise of curve _B_ to the right of
X-X′, the line of transition, and its higher elevation above its former
saturation level, as contrasted with _A_, indicates greater dryness
(lower relative humidity). There has been precipitation in case _A_, but
at a higher temperature, hence more water vapor remains in the air
after precipitation has ceased. Curve _B_ ultimately rises nearly to the
level of _A_, for with less water vapor in the air of case _B_ the
temperature rises more rapidly (a general law). Moreover, the higher the
temperature the greater the radiation. To summarize, curve _A_ rises
more slowly than curve _B_, (1) because of the greater amount of water
vapor it contains, which must have its temperature raised with that of
the air, and thus absorbs energy which would otherwise go to increase
the temperature of the air, and (2) because its loss of heat by
radiation is more rapid on account of its higher temperature. We
conclude from these principles and deductions that under the given
conditions a cold current intensifies, but does not cause the aridity of
the west-coast desert.

[Illustration: FIG. 77--To show progressive lowering of saturation
temperature in a desert under the influence of the mixing process
whereby dry and cool air from aloft sinks to lower levels thus
displacing the warm surface air of the desert. The evaporated moisture
of the surface air is thus distributed through a great volume of upper
air and rain becomes increasingly rarer. Applied to deserts in general
it shows that the effect of any cosmic agent in producing climatic
change from moist to dry or dry to moist will be disproportionately
increased. The shaded areas C and C’ represent the fog-covered slopes of
the Coast Range of Peru as shown in Fig. 92. X-X’ represents the crest
of the Coast Range.]

Curves _a_ and _b_ represent the rise of temperature in two contrasted
cases of warm and cold sea with the coastal mountains eliminated, so as
to simplify the principle applied to _A_ and _B_. The steeper gradient
of _b_ also represents the fact that the lower the initial temperature
the dryer will the air become in passing over the warm land. For these
two curves the transition line X-X’ coincides with the crest of the
Coast Range. It will also be seen that curve _a_ is never so far from
the saturation level as curve _b_. Hence, unusual atmospheric
disturbances would result in heavier and more frequent showers.

[Illustration: FIG. 78--Wind roses for Callao. The figures for the
earlier period (1897-1900) are drawn from data in the Boletín de la
Sociedad Geográfica de Lima, Vols. 7 and 8, 1898-1900: for the latter
period data from observations of Captain A. Taylor, of Callao. The
diameter of the circle represents the proportionate number of
observations when calm was registered.]

[Illustration: FIG. 79--Wind roses for Mollendo. The figures are drawn
from data in Peruvian Meteorology (1892-1895), Annals of the
Astronomical Observatory of Harvard College, Vol. 30, Pt. 2, Cambridge,
Mass., 1906. Observations for an earlier period, Feb. 1889-March 1890,
(Id. Vol. 39, Pt. 1, Cambridge, Mass. 1890) record S. E. wind at 2 p. m.
97 per cent of the observation time.]

[Illustration: FIG. 80--Wind roses for the summer and winter seasons of
the years 1911-1913. The diameter of the circle in each case shows the
proportion of calm. Figures are drawn from data in the Anuario
Meteorológico de Chile, Publications No. 3, (1911), 6 (1912) and 13
(1913), Santiago, 1912, 1914, 1914.]

Turning now to local factors we find on the west coast a regional
topography that favors a diurnal periodicity of air movement. The strong
slopes of the Cordillera and the Coast Range create up-slope or eastward
air gradients by day and opposite gradients by night. To this
circumstance, in combination with the low temperature of the ocean water
and the direction of the prevailing winds, is due the remarkable
development of the sea-breeze, without exception the most important
meteorological feature of the Peruvian Coast. Several graphic
representations are appended to show the dominance of the sea-breeze
(see wind roses for Callao, Mollendo, Arica, and Iquique), but interest
in the phenomenon is far from being confined to the theoretical.
Everywhere along the coast the _virazon_, as the sea-breeze is called in
contradistinction to the _terral_ or land-breeze, enters deeply into the
affairs of human life. According to its strength it aids or hinders
shipping; sailing boats may enter port on it or it may be so violent,
as, for example, it commonly is at Pisco, that cargo cannot be loaded or
unloaded during the afternoon. On the nitrate pampa of northern Chile
(20° to 25° S.) it not infrequently breaks with a roar that heralds its
coming an hour in advance. In the Majes Valley (12° S.) it blows gustily
for a half-hour and about noon (often by eleven o’clock) it settles down
to an uncomfortable gale. For an hour or two before the sea-breeze
begins the air is hot and stifling, and dust clouds hover about the
traveler. The maximum temperature is attained at this time and not
around 2.00 P. M. as is normally the case. Yet so boisterous is the noon
wind that the laborers time their siesta by it, and not by the high
temperatures of earlier hours. In the afternoon it settles down to a
steady, comfortable, and dustless wind, and by nightfall the air is once
more calm.

[Illustration: FIG. 81--Wind roses for Iquique for the summer and winter
seasons of the years 1911-1913. The diameter of the circle in each case
shows the proportion of calm. For source of data see Fig. 80.]

Of highest importance are the effects of the sea-breeze on
precipitation. The bold heights of the Coast Range force the nearly or
quite saturated air of the sea-wind to rise abruptly several thousand
feet, and the adiabatic cooling creates fog, cloud, and even rain on the
seaward slope of the mountains. The actual form and amount of
precipitation both here and in the interior region vary greatly,
according to local conditions and to season and also from year to year.
The coast changes height and contour from place to place. At Arica the
low coastal chain of northern Chile terminates at the Morro de Arica.
Thence northward is a stretch of open coast, with almost no rainfall and
little fog. But in the stretch of coast between Mollendo and the Majes
Valley a coastal range again becomes prominent. Fog enshrouds the hills
almost daily and practically every year there is rain somewhere along
their western aspect.

[Illustration: FIG. 82--The wet and dry seasons of the Coast Range and
the Cordillera are complementary in time. The “wet” season of the former
occurs during the southern winter; the cloud bank on the seaward slopes
of the hills is best developed at that time and actual rains may occur.]

[Illustration: FIG. 83--During the southern summer the seaward slopes of
the Coast Range are comparatively clear of fog. Afternoon cloudiness is
characteristic of the desert and increases eastward (compare Fig. 86),
the influence of the strong sea winds as well as that of the trades
(compare Fig. 93B) being felt on the lower slopes of the Maritime
Cordillera.]

During the southern winter the cloud bank of the coast is best developed
and precipitation is greatest. At Lima, for instance, the clear skies of
March and April begin to be clouded in May, and the cloudiness grows
until, from late June to September, the sun is invisible for weeks at a
time. This is the period of the garua (mist) or the “tiempo de lomas,”
the “season of the hills,” when the moisture clothes them with verdure
and calls thither the herds of the coast valleys.

[Illustration: FIG. 84--Cloudiness at Callao. Figures are drawn from
data in the Boletín de la Sociedad Geográfica de Lima, Vols. 7 and 8,
1898-1900. They represent the conditions at three observation hours
during the summers (Dec., Jan.) of 1897-1898, 1898-1899, 1899-1900 and
the winters (June, July) of 1898 and 1899.]

During the southern summer on account of the greater relative difference
between the temperatures of land and water, the sea-breeze attains its
maximum strength. It then accomplishes its greatest work in the desert.
On the pampa of La Joya, for example, the sand dunes move most rapidly
in the summer. According to the Peruvian Meteorological Records of the
Harvard Astronomical Observatory the average movement of the dunes from
April to September, 1900, was 1.4 inches per day, while during the
summer months of the same year it was 2.7 inches. In close agreement are
the figures for the wind force, the record for which also shows that 95
per cent of the winds with strength over 10 miles per hour blew from a
southerly direction. Yet during this season the coast is generally
clearest of fog and cloud. The explanation appears to lie in the
exceedingly delicate nature of the adjustments between the various
rain-making forces. The relative humidity of the air from the sea is
always high, but on the immediate coast is slightly less so in summer
than in winter. Thus in Mollendo the relative humidity during the winter
of 1895 was 81 per cent; during the summer 78 per cent. Moreover, the
temperature of the Coast Range is considerably higher in summer than in
winter, and there is a tendency to reëvaporation of any moisture that
may be blown against it. The immediate shore, indeed, may still be
cloudy as is the case at Callao, which actually has its cloudiest season
in the summer but the hills are comparatively clear. In consequence the
sea-air passes over into the desert, where the relative increase in
temperature has not been so great (compare Mollendo and La Joya in the
curve for mean monthly temperature), with much higher vapor content than
in winter. The relative humidity for the winter season at La Joya, 1895,
was 42.5 per cent; for the summer season 57 per cent. The influence of
the great barrier of the Maritime Cordillera, aided doubtless by
convectional rising, causes ascent of the comparatively humid air and
the formation of cloud. Farther eastward, as the topographic influence
is more strongly felt, the cloudiness increases until on the border
zone, about 8,000 feet in elevation, it may thicken to actual rain. Data
have been selected to demonstrate this eastern gradation of
meteorological phenomena.

[Illustration: FIG. 85--Temperature curves for Mollendo (solid lines)
and La Joya (broken lines) April, 1894, to December, 1895, drawn from
data in Peruvian Meteorology, 1892-1895, Annals of the Astronomical
Observatory of Harvard College, Vol. 49, Pt. 2, Cambridge, Mass., 1908.
The approximation of the two curves of maximum temperature during the
winter months contrasts with the well-maintained difference in minimum
temperatures throughout the year.]

[Illustration: FIG. 86--Mean monthly cloudiness for Mollendo (solid
line) and La Joya (broken line) from April, 1892, to December, 1895.
Mollendo, 80 feet elevation, has the maximum winter cloudiness
characteristic of the seaward slope of the Coast Range (compare Fig. 82)
while the desert station of La Joya, 4,140 feet elevation, has typical
summer cloudiness (compare Fig. 83). Figures are drawn from data in
Peruvian Meteorology, 1892-1895, Annals of the Astronomical Observatory
of Harvard College, Vol. 49, Pt. 2, Cambridge, Mass., 1908.]

[Illustration: FIG. 87--Wind roses for La Joya for the period April,
1892, to December, 1895. Compare the strong afternoon indraught from the
south with the same phenomenon at Mollendo, Fig. 79. Figures drawn from
data in Peruvian Meteorology, 1892-1895, Annals of the Astronomical
Observatory of Harvard College, Vol. 39, Pt. 2, Cambridge, Mass., 1906.]

At La Joya, a station on the desert northeast of Mollendo at an
elevation of 4,140 feet, cloudiness is always slight, but it increases
markedly during the summer. Caraveli, at an altitude of 5,635 feet,[22]
and near the eastern border of the pampa, exhibits a tendency toward the
climatic characteristics of the adjacent zone. Data for a camp station
out on the pampa a few leagues from the town, were collected by Mr. J.
P. Little of the staff of the Peruvian Expedition of 1912-13. They
relate to the period January to March, 1913. Wind roses for these months
show the characteristic light northwesterly winds of the early morning
hours, in sharp contrast with the strong south and southwesterly
indraught of the afternoon. The daily march of cloudiness is closely
coördinated. Quotations from Mr. Little’s field notes follow:

“In the morning there is seldom any noticeable wind. A breeze starts at
10 A. M., generally about 180° (i. e. due south), increases to 2 or 3
velocity at noon, having veered some 25° to the southwest. It reaches a
maximum velocity of 3 to 4 at about 4.00 P. M., now coming about 225°
(i. e. southwest). By 6 P. M. the wind has died down considerably and
the evenings are entirely free from it. The wind action is about the
same every day. It is not a cold wind and, except with the fog, not a
damp one, for I have not worn a coat in it for three weeks. It has a
free unobstructed sweep across fairly level pampas.... At an interval of
every three or four days a dense fog sweeps up from the southwest, dense
enough for one to be easily lost in it. It seldom makes even a sprinkle
of rain, but carries heavy moisture and will wet a man on horseback in
10 minutes. It starts about 3 P.M. and clears away by 8.00 P. M.....
During January, rain fell in camp twice on successive days, starting at
3.00 P. M. and ceasing at 8.00 P. M. It was merely a light, steady rain,
more the outcome of a dense fog than a rain-cloud of quick approach. In
Caraveli, itself, I am told that it rains off and on all during the
month in short, light showers.” This record is dated early in February
and, in later notes, that month and March are recorded rainless.

[Illustration: FIG. 88--Wind roses for a station on the eastern border
of the Coast Desert near Caraveli during the summer (January to March)
of 1913. Compare with Fig. 87. The diameter of the circle in each case
represents the proportion of calm. Note the characteristic morning
calm.]

Chosica (elevation 6,600 feet), one of the meteorological stations of
the Harvard Astronomical Observatory, is still nearer the border. It
also lies farther north, approximately in the latitude of Lima, and this
in part may help to explain the greater cloudiness and rainfall. The
rainfall for the year 1889-1890 was 6.14 inches, of which 3.94 fell in
February. During the winter months when the principal wind observations
were taken, over 90 per cent showed noon winds from a southerly
direction while in the early morning northerly winds were frequent. It
is also noteworthy that the “directions of the upper currents of the
atmosphere as recorded by the motion of the clouds was generally between
N. and E.” Plainly we are in the border region where climatic influences
are carried over from the plateau and combine their effects with those
from Pacific sources. Arequipa, farther south, and at an altitude of
7,550 feet, resembles Chosica. For the years 1892 to 1895 its mean
rainfall was 5.4 inches.

[Illustration: FIG. 89--Cloudiness at the desert station of Fig. 88
(near Caraveli), for the summer (January to March) of 1913.]

Besides the seasonal variations of precipitation there are longer
periodic variations that are of critical importance on the Coast Range.
At times of rather regular recurrence, rains that are heavy and general
fall there. Every six or eight years is said to be a period of rain, but
the rains are also said to occur sometimes at intervals of four years or
ten years. The regularity is only approximate. The years of heaviest
rain are commonly associated with an unusual frequency of winds from the
north, and an abnormal development of the warm current, El Niño, from
the Gulf of Guayaquil. Such was the case in the phenomenally rainy year
of 1891. The connection is obscure, but undoubtedly exists.

The effects of the heavy rains are amazing and appear the more so
because of the extreme aridity of the country east of them. During the
winter the desert traveler finds the air temperature rising to
uncomfortable levels. Vegetation of any sort may be completely lacking.
As he approaches the leeward slope of the Coast Range, a cloud mantle
full of refreshing promise may be seen just peeping over the crest (Fig.
91). Long, slender cloud filaments project eastward over the margin of
the desert. They are traveling rapidly but they never advance far over
the hot wastes, for their eastern margins are constantly undergoing
evaporation. At times the top of the cloud bank rises well above the
crest of the Coast Range, and it seems to the man from the temperate
zone as if a great thunderstorm were rising in the west. But for all
their menace of wind and rain the clouds never get beyond the desert
outposts. In the summer season the aspect changes, the heavy yellow sky
of the desert displaces the murk of the coastal mountains and the
bordering sea.

[Illustration: FIG. 90--Cloudiness at Chosica, July, 1889, to September,
1890. Chosica, a station on the Oroya railroad east of Lima, is situated
on the border region between the desert zone of the coast and the
mountain zone of yearly rains. The minimum cloudiness recorded about 11
a. m. is shown by a broken line; the maximum cloudiness, about 7 p. m.,
by a dotted line, and the mean for the 24 hours by a heavy solid line.
The curves are drawn from data in Peruvian Meteorology, 1889-1890,
Annals of the Astronomical Observatory of Harvard College, Vol. 39, Pt.
1, Cambridge, Mass., 1899.]

It is an age-old strife renewed every year and limited to a narrow field
of action, wonderfully easy to observe. We saw it in its most striking
form at the end of the winter season in October, 1911, and for more than
a day watched the dark clouds rise ominously only to melt into nothing
where the desert holds sway. At night we camped beside a scum-coated
pool of alkali water no larger than a wash basin. It lay in a valley
that headed in the Coast Range, and carried down into the desert a mere
trickle that seeped through the gravels of the valley floor. A little
below the pool the valley cuts through a mass of granite and becomes a
steep-walled gorge. The bottom is clogged with waste, here boulders,
there masses of both coarse and fine alluvium. The water in the valley
was quite incapable of accomplishing any work except that associated
with solution and seepage, and we saw it in the wet season of an
unusually wet year. Clearly there has been a diminution in the water
supply. But time prevented us from exploring this particular valley to
its head, to see if the reduction were due to a change of climate, or
only to capture of the head-waters by the vigorous rain-fed streams that
enjoy a favorable position on the wet seaward slopes and that are
extending their watershed aggressively toward the east at the expense of
their feeble competitors in the dry belt.

An early morning start enabled me to witness the whole series of changes
between the clear night and the murky day, and to pass in twelve hours
from the dry desert belt through the wet belt, and emerge again into the
sunlit terraces at the western foot of the Coast Range. Two hours before
daylight a fog descended from the hills and the going seemed to be
curiously heavy for the beasts. At daybreak my astonishment was great to
find that it was due to the distinctly moist sand. We were still in the
desert. There was not a sign of a bush or a blade of grass. Still, the
surface layer, from a half inch to an inch thick, was really wet. The
fog that overhung the trail lifted just before sunrise, and at the first
touch of the sun melted away as swiftly as it had come. With it went the
surface moisture and an hour after sunrise the dust was once more rising
in clouds around us.

We had no more than broken camp that morning when a merchant with a
pack-train passed us, and shouted above the bells of the leading animals
that we ought to hurry or we should get caught in the rain at the pass.
My guide, who, like many of his kind, had never before been over the
route he pretended to know, asked him in heaven’s name what drink in
distant Camaná whence he had come produced such astonishing effects as
to make a man talk about rain in a parched desert. We all fell to
laughing and at our banter the stranger stopped his pack-train and
earnestly urged us to hurry, for, he said, the rains beyond the pass
were exceptionally heavy this year. We rode on in a doubtful state of
mind. I had heard about the rains, but I could not believe that they
fell in real showers!

About noon the cloud bank darkened and overhung the border of the
desert. Still the sky above us was clear. Then happened what I can yet
scarcely believe. We rode into the head of a tiny valley that had cut
right across the coast chain. A wisp of cloud, an outlier of the main
bank, lay directly ahead of us. There were grass and bushes not a
half-mile below the bare dry spot on which we stood. We were riding down
toward them when of a sudden the wind freshened and the cloud wisp
enveloped us, shutting out the view, and ten minutes later the moisture
had gathered in little beads on the manes of our beasts and the trail
became slippery. In a half-hour it was raining and in an hour we were in
the midst of a heavy downpour. We stopped and pastured our famished
beasts in luxuriant clover. While they gorged themselves a herd of
cattle drifted along, and a startled band of burros that suddenly
confronted our beasts scampered out of sight in the heavy mist. Later we
passed a herdsman’s hut and long before we reached him he shouted to us
to alter our course, for just ahead the old trail was wet and
treacherous at this time of year. The warning came too late. Several of
our beasts lost their footing and half rolled, half slid, down hill. One
turned completely over, pack and all, and lay in the soft mud calmly
taking advantage of the delay to pluck a few additional mouthfuls of
grass. We were glad to reach firmer ground on the other side of the
valley.

The herdsmen were a hospitable lot. They had come from Camaná and rarely
saw travelers. Their single-roomed hut was mired so deeply that one
found it hard to decide whether to take shelter from the rain inside or
escape the mud by standing in the rain outside. They made a little
so-called cheese, rounded up and counted the cattle on clear days,
drove them to the springs from time to time, and talked incessantly of
the wretched rains in the hills and the delights of dry Camaná down on
the coast. We could not believe that only some hours’ traveling
separated two localities so wholly unlike.

The heavy showers and luxuriant pastures of the wet years and the light
local rains of the dry years endow the Coast Range with many peculiar
geographic qualities. The heavy rains provide the desert people at the
foot of the mountains such a wealth of pasture for their burdensome
stock as many oases dwellers possess only in their dreams. From near and
far cattle are driven to the wet hill meadows. Some are even brought in
from distant valleys by sea, yet only a very small part of the rich
pastures can be used. It is safe to say that they could comfortably
support ten times the number of cattle, mules, and burros that actually
graze upon them. The grass would be cut for export if the weather were
not so continually wet and if there were not so great a mixture of
weeds, flowers, and shrubs.

Then come the dry years. The surplus stock is sold, and what remains is
always maintained at great expense. In 1907 I saw stock grazing in a
small patch of dried vegetation back of Mollendo, although they had to
be driven several miles to water. They looked as if they were surviving
with the greatest difficulty and their restless search for pasture was
like the search of a desperate hunter of game. In 1911 the same tract
was quite devoid of grass, and except for the contour-like trails that
completely covered the hills no one would even guess that this had
formerly been a cattle range. The same year, but five months later, a
carpet of grass, bathed in heavy mist, covered the soil; a trickle of
water had collected in pools on the valley floor; several happy families
from the town had laid out a prosperous-looking garden; there were
romping children who showed me where to pick up the trail to the port;
on every hand was life and activity because the rains had returned
bringing plenty in their train. I asked a native how often he was
prosperous.

“Segun el temporal y la Providencia” (according to the weather and to
Providence), he replied, as he pointed significantly to the pretty green
hills crowned with gray mist.

It, therefore, seems fortunate that the Coast Range is so placed as to
intercept and concentrate a part of the moisture that the sea-winds
carry, and doubly fortunate that its location is but a few miles from
the coast, thereby giving temporary relief to the relatively crowded
people of the lower irrigated valleys and the towns. The wet years
formerly developed a crop of prospectors. Pack animals are cheaper when
there is good pasture and they are also easier to maintain. So when the
rains came the hopeful pick-and-shovel amateurs began to emigrate from
the towns to search for ore among the discolored bands of rock intruded
into the granite masses of the coastal hills. However, the most likely
spots have been so thoroughly and so unsuccessfully prospected for many
years that there is no longer any interest in the “mines.”

Transportation rates are still most intimately related to the rains. My
guide had two prices--a high price if I proposed to enter a town at
night and thus require him to buy expensive forage; a low price if I
camped in the hills and reached the town in time for him to return to
the hills with his animals. Inquiry showed that this was the regular
custom. I also learned that in packing goods from one part of the coast
to another forage must be carried in dry years or the beasts required to
do without. In wet years by a very slight detour the packer has his
beasts in good pasture that is free for all. The merchant who dispatches
the goods may find his charges nearly doubled in extremely dry years.
Goods are more expensive and there is a decreased consumption. The
effects of the rains are thus transmitted from one to another, until at
last nearly all the members of a community are bearing a share of the
burdens imposed by drought. As always there are a few who prosper in
spite of the ill wind. If the pastures fail, live stock _must_ be sold
and the dealers ship south to the nitrate ports or north to the large
coast towns of Peru, where there is always a demand. Their business is
most active when it is dry or rather at the beginning, of the dry
period. Also if transport by land routes becomes too expensive the small
traders turn to the sea routes and the carriers have an increased
business. But so far as I have been able to learn, dry years favor only
a few scattered individuals.

To the traveler on the west coast it is a source of constant surprise
that the sky is so often overcast and the ports hidden by fog, while on
every hand there are clear evidences of extreme aridity. Likewise it is
often inquired why the sunsets there should be often so superlatively
beautiful during the winter months when the coast is fog bound. Why a
desert when the air is so humid? Why striking sunsets when so many of
the days are marked by dull skies? As we have seen in the first part of
this chapter, the big desert tracts lie east of the Coast Range, and
there, excepting slight summer cloudiness, cloudless skies are the rule.
The desert just back of the coast is in many parts of Peru only a narrow
fringe of dry marine terraces quite unlike the real desert in type of
weather and in resources. The fog bank overhanging it forms over the
Humboldt Current which lies off shore; it drifts landward with the
onshore wind; it forms over the upwelling cold water between the current
and the shore; it gathers on the seaward slopes of the coastal hills as
the inflowing air ascends them in its journey eastward. Sometimes it
lies on the surface of the land and the water; more frequently it is
some distance above them. On many parts of the coast its characteristic
position is from 2,000 to 4,000 feet above sea level, descending at
night nearly or quite to the surface, ascending by day and sometimes all
but disappearing except as rain-clouds on the hills.[23] Upon the local
behavior of the fog bank depends in large measure the local climate. A
general description of the coastal climate will have many exceptions.
The physical principles involved are, however, the same everywhere. I
take for discussion therefore the case illustrated by Fig. 92, since
this also displays with reasonable fidelity the conditions along that
part of the Peruvian coast between Camaná and Mollendo which lies in the
field of work of the Yale Peruvian Expedition of 1911.

Three typical positions of the fog bank are shown in the figure, and a
fourth--that in which the bank extends indefinitely westward--may be
supplied by the imagination.

If the cloud bank be limited to _C_ only the early morning hours at the
port are cloudy. If it extend to _B_ the sun is obscured until midday.
If it reach as far west as _A_ only a few late afternoon hours are
sunny. Once in a while there is a sudden splash of rain--a few drops
which astonish the traveler who looks out upon a parched landscape. The
smaller drops are evaporated before reaching the earth. In spite of the
ever-present threat of rain the coast is extremely arid. Though the
vegetation appears to be dried and burned up, the air is humid and for
months the sky may be overcast most of the time. So nicely are the
rain-making conditions balanced that if one of our ordinary low-pressure
areas, or so-called cyclonic storms, from the temperate zone were set in
motion along the foot of the mountains, the resulting deluge would
immediately lay the coast in ruins. The cane-thatched, mud-walled huts
and houses would crumble in the heavy rain like a child’s sand pile
before a rising sea; the alluvial valley land would be coated with
infertile gravel; and mighty rivers of sand, now delicately poised on
arid slopes, would inundate large tracts of fertile soil.

[Illustration: FIG. 91--Looking down the canyon of the Majes River to
the edge of the cloud bank formed against the Coast Range back of
Camaná.]

[Illustration: FIG. 92--Topographic and climatic cross-section to show
the varying positions of the cloud bank on the coast of Peru, the dry
terrace region, and the types of stream profiles in the various belts.]

If the fog and cloud bank extend westward indefinitely, the entire day
may be overcast or the sun appear for a few moments only through
occasional rifts. Generally, also, it will make an appearance just
before sunset, its red disk completely filling the narrow space between
the under surface of the clouds and the water. I have repeatedly seen
the ship’s passengers and even the crew leave the dinner table and
collect in wondering groups about the port-holes and doorways the better
to see the marvelous play of colors between sky and sea. It is
impossible not to be profoundly moved by so majestic a scene. A long
resplendent path of light upon the water is reflected in the clouds.
Each cloud margin is tinged with red and, as the sun sinks, the long
parallel bands of light are shortened westward, changing in color as
they go, until at last the full glory of the sunset is concentrated in a
blazing arc of reds, yellows, and purples, that to most people quite
atones for the dull gray day and its humid air.

At times the clouds are broken up by the winds and scattered
helter-skelter through the west. A few of them may stray into the path
of the sun temporarily to hide it and to reflect its primary colors when
the sun reappears. From the main cloud masses there reach out slender
wind-blown streamers, each one delicately lighted as the sun’s rays
filter through its minute water particles. Many streamers are visible
for only a short distance, but when the sun catches them their filmy
invisible fingers become delicate bands of light, some of which rapidly
grow out almost to the dome of the sky. Slowly they retreat and again
disappear as the rays of the sun are gradually shut off by the upturning
curve of the earth.

The unequal distribution of precipitation in the climatic zones of
western Peru has important hydrographic consequences. These will now be
considered. In the preceding figure four types of stream profiles are
displayed and each has its particular relation to the cloud bank. Stream
1 is formed wholly upon the coastal terraces beneath the cloud bank. It
came into existence only after the uplift of the earth’s crust that
brought the wave-cut platforms above sea level. It is extremely youthful
and on account first of the small seepage at its headquarters--it is
elsewhere wholly without a tributary water supply--and, second, of the
resistant granite that occurs along this part of the coast, it has very
steep and irregular walls and an ungraded floor. Many of these
“quebradas” are difficult to cross. A few of them have fences built
across their floors to prevent the escape of cattle and burros that
wander down from the grassy hills into the desert zone. Others are
partitioned off into corrals by stone fences, the steep walls of the
gorge preventing the escape of the cattle. To these are driven the
market cattle, or mules and burros that are required for relays along
the shore trail.

Stream 2 heads in the belt of rains. Furthermore it is a much older
stream than 1, since it dates back to the time when the Coast Range was
first formed. It has ample tributary slopes and a large number of small
valleys. A trickle of water flows down to become lost in the alluvium of
the lower part of the valley or to reappear in scattered springs. Where
springs and seepage occur together, an olive grove or a garden marks the
spot, a corral or two and a mud or stone or reed hut is near by, and
there is a tiny oasis. Some of these dots of verdure become so dry
during a prolonged drought that the people, long-established, move away.
To others the people return periodically. Still others support permanent
settlements.

Stream 3 has still greater age. Its only competitors are the feeble,
almost negligible, streams that at long intervals flow east toward the
dry zone. Hence it has cut back until it now heads in the desert. Its
widely branched tributaries gather moisture from large tracts. There is
running water in the valley floor even down in the terrace zone. At
least there are many dependable springs and the permanent homes that
they always encourage. A valley of this type is always marked by a
well-defined trail that leads from settlement to settlement and eastward
over the “pass” to the desert and the Andean towns.

Stream 4 is a so-called “antecedent” stream. It existed before the Coast
Range was uplifted and cut its channel downward as the mountains rose in
its path. The stretch where it crosses the mountains may be a canyon
with a narrow, rocky, and uncultivable floor, so that the valley trails
rise to a pass like that at the head of stream 3, and descend again to
the settlements at the mouth of 4. There is in this last type an
abundance of water, for the sources of the stream are in the zone of
permanent snows and frequent winter rains of the lofty Cordillera of the
Andes. The settlements along this stream are continuous, except where
shut-ins occur--narrow, rocky defiles caused by more resistant rock
masses in the path of the stream. Here and there are villages. The
streams have fish. When the water rises the river may be unfordable and
people on opposite sides must resort to boats or rafts.[24]

EASTERN BORDER CLIMATES

On windward mountain slopes there is always a belt of maximum
precipitation whose elevation and width vary with the strength of the
wind, with the temperature, and with the topography. A strong and
constant wind will produce a much more marked concentration of the
rainfall. The belt is at a low elevation in high latitudes and at a high
elevation in low latitudes, with many irregularities of position
dependent upon the local and especially the minimum winter temperature.
The topographic controls are important, since the rain-compelling
elevation may scatter widely the localities of maximum precipitation or
concentrate them within extremely narrow limits. The human effects of
these climatic conditions are manifold. Wherever the heaviest rains are,
there, too, as a rule, are the densest forests and often the most
valuable kinds of trees. If the general climate be favorable and the
region lie near dense and advanced populations, exploitation of the
forest and progress of the people will go hand in hand. If the region be
remote and some or all of the people in a primitive state, the forest
may hinder communication and retard development, especially if it lie in
a hot zone where the natural growth of population is slow.... These are
some of the considerations we shall keep in mind while investigating the
climate of the eastern border of the Peruvian Andes.

[Illustration: FIG. 93A--Cloud types and rainfall belts on the eastern
border of the Peruvian Andes in the dry season, southern winter. The
zone of maximum rainfall extends approximately from 4,000 to 10,000 feet
elevation.]

[Illustration: FIG. 93B--Cloud types and rainfall belts on the eastern
border of the Peruvian Andes in the wet season, southern summer.]

The belt of maximum precipitation on the eastern border of the Andean
Cordillera in Peru lies between 4,000 and 10,000 feet. Judging by the
temporary records of the expedition and especially by the types of
forest growth, the heaviest rains occur around 8,000 feet. It is between
these elevations that the densest part of the Peruvian _montaña_
(forest) is found. The cold timber line is at 10,500 feet with
exceptional extensions of a few species to 12,500 feet. In basins or
deep secluded valleys near the mountain border, a dry timber line occurs
at 3,000 feet with many variations in elevation due to the variable
declivity and exposure of the slopes and degree of seclusion of the
valleys. Elsewhere, the mountain forest passes without a break into the
plains forest with change in type but with little change in density. The
procumbent and suppressed trees of the cold timber line in regions of
heavy winter snows are here absent, for the snows rarely reach below
14,000 feet and even at that elevation they are only light and
temporary. The line of perpetual snow is at 15,000 feet. This permanent
gap of several thousand feet vertical elevation between the zone of snow
and the zone of forest permits the full extension of many pioneer forest
species, which is to say, there is an irregular development of the cold
timber line. It also permits the full use of the pasture belt above the
timber (Fig. 97), hence permanent habitations exist but little below the
snowline and a group of distinctive high-mountain folk enjoys a wide
distribution. There is a seasonal migration here, but it is not
wholesale; there are pastures snow-covered in the southern winter, but,
instead of the complete winter burial of the Alpine meadows of our
western mountains, we have here only a buried upper fringe. All the rest
of the pasture belt is open for stock the year round.

This climatic distinction between the lofty grazing lands of the tropics
and those of the temperate zones is far-reaching. Our mountain forests
are not utilized from above but from below. Furthermore, the chief ways
of communication lead around our forests, or, if through them, only for
the purpose of putting one population group in closer touch with
another. In the Peruvian Andes the largest population groups live above
the forest, not below it or within it. It must be and is exploited from
above.

Hence railways to the eastern valleys of Peru have two chief objects,
(1) to get the plantation product to the dense populations above the
forest and (2) to bring timber from the _montaña_ to the treeless
plateau. The mountain prospector is always near a habitation; the rubber
prospector goes down into the forested valleys and plains far from
habitations. The forest separates the navigable streams from the chief
towns of the plateau; it does not lead down to rich and densely
populated valley floors.

Students in eastern Peru should find it a little difficult to understand
poetical allusions to silent and lonely highlands in contrast to the
busy life of the valleys. To them Shelley’s description of the view from
the Euganean Hills of northern Italy,

“Beneath is spread like a green sea
The waveless plain of Lombardy, ...
Islanded by cities fair,”

might well seem to refer to a world that is upside down.

There is much variation in the forest types between the mountains and
the plains. At the top of the forest zone the warm sunny slopes have a
forest cover; the shady slopes are treeless. At the lower edge of the
grassland, only the shady slopes are forested (Fig. 53B). Cacti of
arboreal size and form grow on the lofty mountains far above the limits
of the true forest; they also appear at 3,000 feet in modified form,
large, rank, soft-spined, and in dense stands on the semi-arid valley
floors below the dry timber line. Large tracts between 8,000 and 10,000
feet are covered with a forest growth distributed by species--here a
dense stand of one type of tree, there another. This is the most
accessible part of the Peruvian forest and along the larger valleys it
is utilized to some extent. The number of species is more limited,
however, and the best timber trees are lower down. Though often referred
to as jungle, the lowlier growths at the upper edge of the forest zone
have no resemblance to the true jungle that crowds the lowland forest.
They are merely an undergrowth, generally open, though in some places
dense. They are nowhere more dense than many examples from New England
or the West.

Where deep valleys occur near the border of the mountains there is a
semi-arid climate below and a wet climate above, with a correspondingly
greater number of species within short distances of each other. This is
a far more varied forest than at the upper edge of the timber zone or
down on the monotonous plains. It has a higher intrinsic value than any
other. That part of it between the Pongo and Yavero (1,200 to 4,000
feet) is very beautiful, with little undergrowth except a light
ground-cover of ferns. The trees are from 40 to 100 feet in height with
an average diameter of about 15 inches. It would yield from 3,000 to
5,000 board feet per acre exclusive of the palms. There are very few
vines suspended from the forest crown and the trunks run clear from 30
to 60 feet above the ground. Were there plenty of labor and a good
transportation line, these stands would have high economic value. Among
the most noteworthy trees are the soft white cedar, strong and light;
the amarillo and the sumbayllo, very durable in water; the black nogal,
and the black balsam, straight and easy to work; the heavy yunquero,
which turns pink when dry; the chunta or black palm, so hard and
straight and easy to split that wooden nails are made from it; and the
rarer sandy matico, highly prized for dug-out canoes. Also from the
chunta palm, hollow except for a few central fibers, easily removed,
pipes are made to convey water. The cocobolo has a rich brown color and
a glossy surface and is very rare, hence is much sought after for use in
furniture making. Most of these woods take a brilliant polish and
exhibit a richness and depth of color and a beauty of grain that are
rare among our northern woods.

[Illustration: FIG. 94--Cloud belt at 11,000 feet in the Apurimac Canyon
near Incahuasi. For a regional diagram and a climatic cross-section see
Figs. 32 and 33.]

[Illustration: FIG. 95--The tropical forest near Pabellon on the slopes
of the Urubamba Valley. Elevation 3,000 feet (915 m.).]

The plains forest northeast of the mountains is in the zone of moderate
rainfall where there is one long dry season and one long wet season.
When it is dry the daytime temperatures rise rapidly to such high levels
that the relative humidity of the air falls below 50 per cent (Fig.
110). The effect on the vegetation is so marked that many plants pass
into a distinctly wilted condition. On clear days the rapid fall in the
relative humidity is astonishing. By contrast the air on the mountain
border heats more slowly and has a higher relative humidity, because
clouds form almost constantly in the ascending air currents and reflect
and absorb a large part of the heat of the sun’s rays. It is striking to
find large tracts of cane and bamboo on the sand bars and on wet shady
hillslopes in the slope belt, and to pass out of them in going to the
plains with which we generally associate a swamp vegetation. They exist
on the plains, but only in favored, that is to say wet, spots. Larger
and more typical tracts grow farther north where the heavier rains of
the Amazon basin fall.

The floods of the wet tropical season also have a restricting influence
upon the tropical forest. They deliver such vast quantities of water to
the low-gradient lowland streams that the plains rivers double, even
treble, their width and huge pools and even temporary lakes form in the
shallow depressions back of the natural levees. Of trees in the flooded
areas there are only those few species that can grow standing in water
several months each year. There are also cane and bamboo, ferns in
unlimited numbers, and a dense growth of jungle. These are the haunts of
the peccary, the red forest deer, and the jungle cat. Except along the
narrow and tortuous animal trails the country is quite impassable. Thus
for the sturdiest and most useful forest growth the one-wet-one-dry
season zone of the plains has alternately too much and too little water.
The rubber tree is most tolerant toward these conditions. Some of the
best stands of rubber trees in Amazonia are in the southwestern part of
the basin of eastern Peru and Bolivia, where there is the most typical
development of the habitat marked by the seasonal alternation of floods
and high temperatures.

When tropical agriculture is extended to the plains the long dry season
will be found greatly to favor it. The southwestern quadrant of the
Amazon basin, above referred to, is the best agricultural area within
it. The northern limits of the tract are only a little beyond the Pongo.
Thence northward the climate becomes wetter. Indeed the best tracts of
all extend from Bolivia only a little way into southeastern Peru, and
are coincident with the patchy grasslands that are there interspersed
with belts of woodland and forest. Sugar-cane is favored by a climate
that permits rapid growth with a heavy rainfall and a dry season is
required for quality and for the harvest. Rice and a multitude of
vegetable crops are also well suited to this type of climate. Even corn
can be grown in large quantities.

At the present time tropical agriculture is almost wholly confined to
the mountain valleys. The reasons are not wholly climatic, as the above
enumeration of the advantages of the plains suggests. The consuming
centers are on the plateau toward the west and limitation to mule pack
transport always makes distance in a rough country a very serious
problem. The valleys combine with the advantage of a short haul a
climate astonishingly like the one just described. In fact it is even
more extreme in its seasonal contrasts. The explanation is dependent
upon precisely the same principles we have hitherto employed. The front
range of the Andes and the course of the Urubamba run parallel for some
distance. Further, the front range is in many places somewhat higher
than the mountain spurs and knobs directly behind it. Even when these
relations are reversed the front range still acts as a barrier to the
rains for all the deep valleys behind it whose courses are not directly
toward the plains. Thus, one of the largest valleys in Peru, the
Urubamba, drops to 3,400 feet at Santa Ana and to 2,000 feet at
Rosalina, well within the eastern scarp of the Andes. The mountains
immediately about it are from 6,000 to 10,000 feet high. The result is a
deep semi-arid pocket with only a patchy forest (Fig. 54, p. 79).[25] In
places the degree of seclusion from the wind is so great that the scrub,
cacti, and irrigation remind one strongly of the desert on the border of
an oasis, only here the transition is toward forests instead of barren
wastes. The dense forest, or _montaña_, grows in the zone of clouds and
maximum precipitation between 4,000 and 10,000 feet. At the lower limit
it descends a thousand feet farther on shady slopes than it does on
sunny slopes. The continuous forest is so closely restricted to the
cloud belt that in Fig. 99 the two limits may be seen in one photograph.
All these sharply defined limits and contrasts are due to the fact that
the broad valley, discharging through a narrow and remote gorge, is
really to leeward of all the mountains around it. It is like a real
desert basin except in a lesser degree of exclusion from the rains. If
it were narrow and small the rains formed on the surrounding heights
would be carried over into it. Rain on the hills and sunshine in the
valley is actually the day-by-day weather of the dry season. In the wet
season the sky is overcast, the rains are general, though lighter in the
valley pocket, and plants there have then their season of most rapid
growth. The dry season brings plants to maturity and is the time of
harvest. Hence sugar and cacao plantations on a large scale, hence a
varied life in a restricted area, hence a distinct geographic province
unique in South America.

INTER-ANDEAN VALLEY CLIMATES

Not all the deep Andean valleys lie on or near the eastern border. Some,
like the Apurimac and the Marañon, extend well into the interior of the
Cordillera. Besides these deep remote valleys with their distinct
climatic belts are basins, most of them with outlets to the sea--broad
structural depressions occurring in some cases along large and in others
along small drainage lines. The Cuzco basin at 11,000 feet and the
Abancay basin at 6,000 to 8,000 feet are typical. Both have abrupt
borders, narrow outlets, large bordering alluvial fans, and fertile
irrigable soil. Their difference of elevation occurs at a critical
level. Corn will ripen in the Cuzco basin, but cane will not. Barley,
wheat, and potatoes are the staple crops in the one; sugar-cane,
alfalfa, and fruit in the other. Since both are bordered by high
pastures and by mineralized rocks, the deeper Abancay basin is more
varied. If it were not so difficult to get its products to market by
reason of its inaccessibility, the Abancay basin would be the more
important. In both areas there is less rainfall on the basin floor than
on the surrounding hills and mountains, and irrigation is practised, but
the deeper drier basin is the more dependent upon it. Many small high
basins are only within the limits of potato cultivation. They also
receive proportionately more rain. Hence irrigation is unnecessary.
According as the various basins take in one or another of the different
product levels (Fig. 35) their life is meager and unimportant or rich
and interesting.

The deep-valley type of climate has the basin factors more strongly
developed. Below the Canyon of Choqquequirau, a topographic feature
comparable with the Canyon of Torontoy, the Apurimac descends to 3,000
feet, broadens to several miles, and has large alluvial fans built into
it. Its floor is really arid, with naked gravel and rock, cacti stands,
and gnarled shrubs as the chief elements of the landscape. Moreover the
lower part of the valley is the steeper. A former erosion level is
indicated in Fig. 125. When it was in existence the slopes were more
moderate than now and the valley broad and open. Thereupon came uplift
and the incision of the stream to its present level. As a result, a
steep canyon was cut in the floor of a mature valley. Hence the slopes
are in a relation unlike that of most of the slopes in our most familiar
landscapes. The gentle slopes are above, the steep below. The break
between the two, a topographic unconformity, may be distinctly traced.

[Illustration: FIG. 96--Snow-capped mountain, Soiroccocha, north of
Arma, Cordillera Vilcapampa. The blue glacier ice descends almost to the
edge of a belt of extraordinary woodland growing just under the
snowline. The glacier is seen to overhang the valley and to have built
on the steep valley wall terminal moraines whose outer slopes are almost
precipitous.]

[Illustration: FIG. 97--Shrubby vegetation mixed with grass at 14,000
feet (4,270 m.) on the northern or sunny slopes of the Cordillera
Vilcapampa above Pampaconas, a thousand feet below the snowline. The
grass is remarkably profuse and supports the flocks and herds of a
pastoral population.]

[Illustration: FIG. 98--Dense ground cover, typical trees, epiphytes,
and parasites of the tropical rain forest at 2,500-3,000 feet between
Pongo de Mainique and Rosalina.]

[Illustration: FIG. 99--The Urubamba Valley below Santa Ana. On the dry
valley floor is a mixed growth of scattered trees, shrubs and grass,
with shrubs predominating. Higher up a more luxuriant ravine vegetation
appears. On the upper spurs true forest patches occupy the shady slopes.
Finally, in the zone of clouds at the top of the picture is a continuous
forest. See Fig. 17, for regional applications.]

Combined with these topographic features are certain climatic features
of equal precision. Between 7,000 and 13,000 feet is a zone of clouds
oftentimes marked out as distinctly as the belt of fog on the Peruvian
coast.[26] Rarely does it extend across the valley. Generally it hangs
as a white belt on the opposite walls. When the up-valley winds of day
begin to blow it drifts up-valley, oftentimes to be dissolved as it
strikes the warmer slopes of the upper valley, just as its settling
under surface is constantly being dissolved in the warm dry air of the
valley floor. Where the precipitation is heaviest there is a belt of
woodland--dark, twisted trees, moss-draped, wet--a Druid forest. Below
and above the woodland are grassy slopes. At Incahuasi a spur runs out
and down until at last it terminates between two deep canyons. No
ordinary wells could be successful. The ground water must be a thousand
feet down, so a canal, a tiny thing only a few inches wide and deep, has
been cut away up to a woodland stream. Thence the water is carried down
by a contour-like course out of the woodland into the pasture, and so
down to the narrow part of the spur where there is pasture but no
springs or streams.

Corn fields surround the few scattered habitations that have been built
just above the break or shoulder on the valley wall where the woodland
terminates, and there are fine grazing lands. The trails follow the
upper slopes whose gentler contours permit a certain liberty of
movement. Then the way plunges downward over a staircase trail, over
steep boulder-strewn slopes to the arid floor of a tributary where
nature has built a graded route. And so to the still more arid floor of
the main valley, where the ample and moderate slopes of the alluvial
fans with their mountain streams permit plantation agriculture again to
come in.

To these three climates, the western border type, the eastern border
type, and the inter-Andean type, we have given chief attention because
they have the most important human relations. The statistical records of
the expedition as shown in the curves and the discussion that
accompanies them give attention to those climatic features that are of
theoretical rather than practical interest, and are largely concerned
with the conventional expression of the facts of weather and climate.
They are therefore combined in the following chapter which is devoted
chiefly to a technical discussion of the meteorology as distinguished
from the climatology of the Peruvian Andes.

CHAPTER X

METEOROLOGICAL RECORDS FROM THE PERUVIAN ANDES

INTRODUCTION

The data in this chapter, on the weather and climate of the Peruvian
Andes, were gathered under the usual difficulties that accompany the
collection of records at camps scarcely ever pitched at the same
elevation or with the same exposure two days in succession. Some of
them, and I may add, the best, were contributed by volunteer observers
at fixed stations. The observations are not confined to the field of the
Yale Peruvian Expedition of 1911, but include also observations from
Professor Hiram Bingham’s Expeditions of 1912 and 1914-15, together with
data from the Yale South American Expedition of 1907. In addition I have
used observations supplied by the Morococha Mining Company through J. P.
Little. Some hitherto unpublished observations from Cochabamba, Bolivia,
gathered by Herr Krüger at considerable expense of money for instruments
and of time from a large business, are also included, and he deserves
the more credit for his generous gift of these data since they were
collected for scientific purposes only and not in connection with
enterprises in which they might be of pecuniary value. My only excuse to
Herr Krüger for this long delay in publication (they were put into my
hands in 1907) is that I have wanted to publish his data in a dignified
form and also to use them for comparison with the data of other climatic
provinces.

A further word to the reader seems necessary before he examines the
following curves and tables. It would be somewhat audacious to assume
that these short-term records have far-reaching importance. Much of
their value lies in their organization with respect to the data already
published on the climate of Peru. But since this would require a delay
of several years in their publication it seems better to present them
now in their simplest form. After all, the professional climatologist,
to whom they are chiefly of interest, scarcely needs to have such
organization supplied to him. Then, too, we hope that there will become
available in the next ten or fifteen years a vastly larger body of
climatological facts from this region. When these have been collected we
may look forward to a volume or a series of volumes on the “Climate of
Peru,” with full statistical tables and a complete discussion of them.
That would seem to be the best time for the reproduction of the detailed
statistics now on hand. It is only necessary that there shall be
sufficient analysis of the data from time to time to give a general idea
of their character and to indicate in what way the scope of the
observations might profitably be extended. I have, therefore, taken from
the available facts only such as seem to me of the most importance
because of their unusual character or their special relations to the
boundaries of plant provinces or of the so-called “natural regions” of
geography.

MACHU PICCHU[27]

The following observations are of special interest in that they
illustrate the weather during the southern winter and spring at the
famous ruins of Machu Picchu in the Canyon of Torontoy. The elevation is
8,500 feet. The period they cover is too short to give more than a hint
of the climate or of the weather for the year. It extends from August
20, 1912, to November 6, 1912 (79 days).

ANALYTICAL TABLE OF WIND DIRECTIONS, MACHU PICCHU, 1912

-----------+--------------------------------------------------------+
| Number of Observations |
Direction +----------------------------+---------------------------|
of wind | Aug. 20 -- Sept. 30 | Oct. 1 -- Nov. 6 |
| 7 a. m. 1 p. m. 7 p. m. | 7 a. m. 1 p. m. 7 p. m. |
-----------+----------------------------+---------------------------+
N. | 5 2 5 | 2 -- -- |
N.W. | 9 10 14 | 4 6 11 |
W. | -- 1 2 | 2 2 4 |
S. W. | -- -- 1 | 1 1 6 |
S. | -- -- 1 | -- -- 2 |
S. E. | 4 2 1 | -- -- 3 |
E. | 6 3 3 | 12 4 4 |
N. E. | 8 7 6 | 4 1 3 |
CALM | -- -- 2 | 5 3 3 |
-----------+----------------------------+---------------------------+

----------------------------------------------------------------+
| Percentages of Total Observation[28] |
Direction|------------------------------------------------------|
of wind | Aug. 20 ---- Sept. 30 | Oct. 1 ---- Nov. 6 |
| 7 a. m. 1 p.m. 7 p. m. | 7 a. m. 1 p. m. 7 p. m.|
----------------------------------------------------------------|
N. | 15.6 8.0 14.2 | 6.7 ---- ---- |
N. W. | 28.1 40.0 40.0 | 13.3 35.3 30.7 |
W. | ---- 4.0 5.7 | 6.7 11.8 11.1 |
S. W. | ---- ---- 2.8 | 3.3 5.9 16.7 |
S. | ---- ---- 2.8 | ---- ---- 5.5 |
S. E. | 12.5 8.0 2.8 | ---- ---- 8.3 |
E. | 18.8 12.0 8.6 | 40.0 23.5 11.1 |
N. E. | 25.0 28.0 17.1 | 13.3 5.9 8.3 |
CALM | ---- ---- 5.7 | 16.7 17.6 8.3 |
----------------------------------------------------------------+

[Illustration: FIG. 100--Wind roses for Machu Picchu, August 20 to
November 6, 1912.]

The high percentage of northwest winds during afternoon hours is due to
the up-valley movement of the air common to almost all mountain borders.
The air over a mountain slope is heated more than the free air at the
same elevation over the plains (or lower valley); hence a barometric
gradient towards the mountain becomes established. At Machu Picchu the
Canyon of Torontoy trends northwest, making there a sharp turn from an
equally sharp northeast bend directly upstream. The easterly components
are unrelated to the topography. They represent the trades. If a wind
rose were made for still earlier morning hours these winds would be more
faithfully represented. That an easterly and northeasterly rather than a
southeasterly direction should be assumed by the trades is not difficult
to believe when we consider the trend of the Cordillera--southeast to
northwest. The observations from here down to the plains all show that
there is a distinct change in wind direction in sympathy with the larger
features of the topography, especially the deep valleys and canyons, the
trades coming in from the northeast.

CLOUDINESS

It will be seen that the sky was overcast or a fog lay in the valley 53
per cent of the time at early morning hours. Even at noon the sky was at
no time clear, and it was more than 50 per cent clear only 18 per cent
of the time. Yet this is the so-called “dry” season of the valleys of
the eastern Andes. The rainfall record is in close sympathy. In the 79
days’ observations rain is recorded on 50 days with a greater proportion
from mid-September to the end of the period (November 6), a distinct
transition toward the wet period that extends from December to May. The
approximate distribution of the rains by hours of observation (7 A. M.,
1 P. M., 7 P. M.) was in the ratio 4:3:6. Also the greatest number of
heavy showers as well as the greatest number of showers took place in
the evening. The rainfall was apparently unrelated to wind direction in
the immediate locality, though undoubtedly associated with the regional
movement of the moist plains air toward the mountains. All these facts
regarding clouds and rain plainly show the location of the place in the
belt of maximum precipitation. There is, therefore, a heavy cover of
vegetation. While the situation is admirable for defence, the murky
skies and frequent fogs somewhat offset its topographic surroundings as
a lookout.

ANALYTICAL TABLE OF THE STATE OF THE SKY, MACHU PICCHU, 1912

---------------+-------------+-------------+
| Morning | Total |
---------------+------+------+------+------+
|Aug.- |Oct.- |Days | % |
|Sept. |Nov. | | |
---------------+------+------+------+------+
Foggy | 3.0 | 14.0 | 17.0 | 28.4 |
Overcast | 12.0 | 3.0 | 15.0 | 25.0 |
50-100% cloudy | 4.0 | 10.0 | 14.0 | 23.3 |
0-50% cloudy | 6.0 | 4.0 | 10.0 | 16.7 |
Clear | 3.0 | 1.0 | 4.0 | 6.6 |
---------------+------+------+------+------+

---------------+-------------+-------------+
| Noon | Total |
---------------+------+------+------+------+
|Aug.- |Oct.- | Days | % |
|Sept. |Nov. | | |
---------------+------+------+------+------+
Foggy | 1.0 | -- | 1.0 | 2.6 |
Overcast | 6.0 | 8.0 | 14.0 | 36.8 |
50-100% cloudy | 0.0 | 7.0 | 16.0 | 42.2 |
0-50% cloudy | 5.0 | 2.0 | 7.0 | 18.4 |
Clear | 0.0 | 0.0 | 0.0 | 0.0 |
---------------+------+------+------+------+

---------------+-------------+-------------
| Evening | Total
---------------+------+------+------+------
|Aug.- |Oct.- |Days | %
|Sept. |Nov. | |
---------------+------+------+------+------
Foggy | 1.0 | 2.0 | 3.0 | 4.3
Overcast | 13.0 | 11.0 | 24.0 | 34.8
50-100% cloudy | 8.0 | 15.0 | 23.0 | 33.3
0-50% cloudy | 9.0 | 4.0 | 13.0 | 18.8
Clear | 3.0 | 3.0 | 6.0 | 8.8
---------------+------+------+------+------

SANTA LUCIA[29]

Santa Lucia is a mining center in the province of Puno (16° S.), at the
head of a valley here running northeast towards Lake Titicaca. Its
elevation, 15,500 feet above sea level, confers on it unusual interest
as a meteorological station. A thermograph has been installed which
enables a closer study of the temperature to be made than in the case of
the other stations. It is unfortunate, however, that the observations
upon clouds, wind directions, etc., should not have been taken at
regular hours. The time ranges from 8.30 to 11.30 for morning hours and
from 2.30 to 5.30 for afternoon. The observations cover portions of the
years 1913 and 1914.

TEMPERATURE

Perhaps the most striking features of the weather of Santa Lucia are the
highly regular changes of temperature from night to day or the uniformly
great diurnal range and the small differences of temperature from day to
day or the low diurnal variability. For the whole period of nearly a
year the diurnal variability never exceeds 9.5° F. (5.3° C.) and for
days at a time it does not exceed 2-3° F. (1.1°-1.7° C.). The most
frequent variation, occurring on 71 per cent of the total number of
days, is from 0-3° F., and the mean for the year gives the low
variability of 1.9° F. (1.06° C.). These facts, illustrative of a type
of weather comparable in _uniformity_ with low stations on the Amazon
plains, are shown in the table following as well as in the accompanying
curves.

FREQUENCY OF THE DIURNAL VARIABILITY, SANTA LUCIA, 1913-14

----------+----+----+----+----+-----+
| | | | | |
Degrees F.|May |June|July|Aug.|Sept.|
----------+----+----+----+----+-----+
0 | -- | 2 | 6 | 3 | 4 |
0-1 | 2 | 7 | 7 | 5 | 6 |
1-2 | 11 | 5 | 7 | 11 | 7 |
2-3 | 2 | 8 | 8 | 9 | 3 |
3-4 | 4 | 4 | 2 | 1 | 4 |
4-5 | 1 | 3 | 1 | -- | 2 |
Over 5 | -- | 1 | -- | 2 | 4 |
----------+----+----+----+----+-----+
Days per| 20 | 30 | 31 | 31 | 30 |
month| | | | | |
----------+----+----+----+----+-----+

----------+----+----+----+----+----+-----++---------
| | | | | | ||Total No.
Degrees F.|Oct.|Nov.|Dec.|Jan.|Feb.|March||of days
----------+----+----+----+----+----+-----++---------
0 | 6 | 2 | -- | 1 | -- | 2 || 26
0-1 | 4 | 8 | 12 | 14 | 9 | 5 || 79
1-2 | 8 | 5 | 5 | 4 | 9 | 13 || 85
2-3 | 7 | 7 | 5 | 5 | 4 | 6 || 64
3-4 | 1 | 3 | 6 | 2 | 4 | 2 || 33
4-5 | 1 | 3 | -- | 2 | 1 | 1 || 15
Over 5 | 4 | 2 | 2 | 3 | 1 | -- || 19
----------+----+----+----+----+----+-----++---------
Days per| 31 | 30 | 30 | 31 | 28 | 29 || 321
month| | | | | | ||
----------+----+----+----+----+----+-----++---------

If we take the means of the diurnal variations by months we have a still
more striking curve showing how little change there is between
successive days. June and December are marked by humps in the curve.
They are the months of extreme weather when for several weeks the
temperatures drop to their lowest or climb to their highest levels.
Moreover, there is at these lofty stations no pronounced lag of the
maximum and minimum temperatures for the year behind the times of
greatest and least heating such as we have at lower levels in the
temperate zone. Thus we have the highest temperature for the year on
December 2, 70.4° F. (21.3° C.), the lowest on June 3, 0.2° F. (--17.7°
C.). The daily maxima and minima have the same characteristic. Radiation
is active in the thin air of high stations and there is a very direct
relation between the times of greatest heat received and greatest heat
contained. The process is seen at its best immediately after the sun is
obscured by clouds. In five minutes I have observed the temperature drop
20° F. (11.1° C.) at 16,000 feet (4,877 m.); and a drop of 10° F. (5.6°
C.) is common anywhere above 14,000 feet (4,267 m.). In the curves of
daily maximum and minimum temperatures we have clearly brought out the
uniformity with which the maxima of high-level stations rise to a mean
level during the winter months (May-August). Only at long intervals is
there a short series of cloudy days when the maximum is 10°-12° F.
(5.6°-6.7° C.) below the normal and the minimum stands at abnormally
high levels. Since clouds form at night in quite variable amounts--in
contrast to the nearly cloudless days--there is a far greater
variability among the minimum temperatures. Indeed the variability of
the winter minima is greater than that of the summer minima, for at the
latter season the nightly cloud cover imposes much more stable
atmospheric temperatures. The summer maxima have a greater degree of
variability. Several clear days in succession allow the temperature to
rise from 5°-10° F. (2.8°-5.6° C.) above the winter maxima. But such
extremes are rather strictly confined to the height of the summer
season--December and January. For the rest of the summer the maxima rise
only a few degrees above those of the winter. This feature of the
climate combines with a December maximum of rainfall to limit the period
of most rapid plant growth to two months. Barley sown in late November
could scarcely mature by the end of January, even if growing on the
Argentine plains and much less at an elevation which carries the night
temperatures below freezing at least once a week and where the mean
temperature hovers about 47° F. (8.3° C.). The proper conditions for
barley growing are not encountered above 13,000 to 13,500 feet and the
farmer cannot be certain that it will ripen above 12,500 feet in the
latitude of Santa Lucia.

The curve of mean monthly temperatures expresses a fact of great
importance in the plant growth at high situations in the Andes--the
sharp break between the winter and summer seasons. There are no real
spring and autumn seasons. This is especially well shown in the curve
for non-periodic mean monthly range of temperature for the month of
October. During the half of the year that the sun is in the southern
hemisphere the sun’s noonday rays strike Santa Lucia at an angle that
varies between 0° and 16° from the vertical. The days and nights are of
almost equal length and though there is rapid radiation at night there
is also rapid insolation by day. When the sun is in the northern
hemisphere the days are shortened from one to two hours and the angle of
insolation decreased, whence the total amount of heat received is so
diminished that the mean monthly temperature lies only a little above
freezing point. In winter the quiet pools beside the springs freeze over
long before dark as the hill shadows grow down into the high-level
valleys, and by morning ice also covers the brooks and marshes. Yet the
sun and wind-cured _ichu_ grass lives here, pale green in summer,
straw-yellow in winter. The tola bush also grows rather abundantly. But
we are almost at the upper limit of the finer grasses and a few hundred
feet higher carries one into the realm of the snowline vegetation,
mosses and lichens and a few sturdy flowering plants.

For convenience in future comparative studies the absolute extremes are
arranged in the following table:

[Illustration: FIG. 101 A--DIURNAL TEMPERATURE, SANTA LUCIA, 1913-’14
C--DIURNAL RANGE OF TEMPERATURE, SANTA LUCIA, 1913-’14 E--DIURNAL
VARIABILITY OF TEMPERATURE, SANTA LUCIA, 1913-’14 B--MEAN MONTHLY
TEMPERATURE, SANTA LUCIA, 1913-’14 D--MONTHLY MEANS OF DIURNAL RANGE OF
TEMPERATURE, SANTA LUCIA, 1913-’14 F--RELATIVE HUMIDITY, SANTA LUCIA,
1913-’14]

ABSOLUTE MONTHLY EXTREMES, SANTA LUCIA, 1913-14

-----------------------+----------++----------+----------------
Date | Highest || Lowest | Date
-----------------------+----------++----------+----------------
May[30] (12) | 62° F. || 9° F. | May (25, 26)
June (4 days) | 60° F. || 0.2° F. | June (3)
July (4 days, 31) | 60° F. || 5° F. | July (8)
Aug. (8, 26) | 62° F. || 4° F. | Aug. (4, 5)
Sept. (several days) | 62° F. || 7° F. | Sept. (4 days)
Oct. (24) | 63° F. || 10° F. | Oct. (12, 13)
Nov. (11)[31] | 63° F. || 24.0° F. | Nov. (29)
Dec. (2) | 70.4° F. || 22.2° F. | Dec. (14)
Jan. (19) | 69.5° F. || 26.5° F. | Jan. (3, 15)
Feb. (16, 18) | 63.2° F. || 30.5° F. | Feb. (23)
March (8) | 68.4° F. || 28.5° F. | March (6)
-----------------------+----------++----------+----------------

RAINFALL

The rainfall record for Santa Lucia is for the year beginning November,
1913. For this period the precipitation amounts to 24.9 inches of which
over 85 per cent fell in the rainy season from November to March. Most
of the rain fell during the violent afternoon tempests that characterize
the summer of these high altitudes.

The rainfall of Santa Lucia for this first year of record approximates
closely to the yearly mean of 23.8 inches for the station of Caylloma in
the adjacent province of that name. Caylloma is the center of a mining
district essentially similar to Santa Lucia though the elevation of its
meteorological station, 14,196 feet (4,330 m.), is lower. It is one of
the few Peruvian stations for which a comparatively long series of
records is available. The _Boletín de la Sociedad Geográfica de
Lima_[32] contains a résumé of rainfall and temperature for seven years,
1896-7 to 1902-3. Later data may be found in subsequent volumes of the
same publication but they have not been summarized or in any way
prepared for analysis and they contain several typographical errors. A
graphic representation of the monthly rainfall for the earlier period is
here reproduced from the _Boletín de minas del Perú_.[33] The amount
of precipitation fluctuates considerably from year to year. For the
earlier period, with a mean of 23.8 inches the minimum (1896-7) was 8
inches and the maximum (1898-9) 36 inches. For the later period, 1903-4
to 1910-11, with a mean of 29.5 inches the minimum (1904-5) was 17.5
inches and the maximum (1906-7) was 43 inches.

[Illustration: FIG. 102--Monthly rainfall of Santa Lucia for the year
November, 1913, to October, 1914. No rain fell in July and August.]

[Illustration: FIG. 103A--Maximum, mean and minimum monthly rainfall of
Caylloma for the period 1896-7 to 1902-3. July was absolutely rainless.
Caylloma is situated immediately east of the crest of the Maritime
Cordillera in a position similar to that of Santa Lucia (see Fig. 66).]

[Illustration: FIG. 103B--Annual rainfall of Caylloma for the periods
1896-7 to 1902-3; 1903-4 to 1910-11 and for 1915-6 (incomplete: May and
June, months of low rainfall, are missing). Means for the respective
seven and eight year periods are shown and the rainfall of Santa Lucia
for the single observation year is inserted for comparison.]

RAINFALL, SANTA LUCIA, NOV. 1913 TO OCT. 1914

---------+---------+----------+----------+---------------
|No of |No. of |Max. for |Total rainfall
|fine days|rainy days|single day|in inches
---------+---------+----------+----------+---------------
November | 9 | 21 | 1.150 | 4.264[34]
December | 16 | 15 | .700 | 6.439
January | 17 | 14 | .610 | 3.313
February | 9 | 17 | .910 | 2.975
March | 11 | 20 | 1.102 | 4.381
April | 17 | 13 | 0.31 | 0.92
May | 8 | 23 | 0.35 | 1.63
June | 27 | 3 | 0.05 | 0.07
July | 31 | 0 | 0.00 | 0.00
August | 31 | 0 | 0.00 | 0.00
September| 23 | 7 | 0.05 | 0.35
October | 21 | 10 | 0.14 | 0.56
---------+---------+----------+----------+---------------
Total | | | | 24.902
---------+---------+----------+----------+---------------

WIND

An analysis of the wind at Santa Lucia shows an excess of north and
south winds over those of all other directions. The wind-rose for the
entire period of observation (Fig. 104) clearly expresses this fact.
When this element is removed we observe a strongly seasonal distribution
of the wind. The winter is the time of north and south winds. In summer
the winds are chiefly from the northeast or the southwest. Among single
months, August and February show this fact clearly as well as the less
decisive character of the summer (February) wind.

The mean wind velocity for the month of February was 540 meters per
minute for the morning and 470 meters per minute for the afternoon. The
higher morning rate, an unusual feature of the weather of high
stations, or indeed of wind-phenomena in general, is due, however, to
exceptional changes in wind strength on two days of the month, the 16th
and 25th, when the velocity decreased from a little less than a thousand
meters per minute in the morning to 4 and 152 meters respectively in the
afternoon. More typical is the March record for 1914 at Santa Lucia,
when the wind was _always_ stronger in the afternoon than in the
morning, their ratios being 550 to 510.

[Illustration: Fig. 104--Monthly wind roses for Santa Lucia, June, 1913,
to July, 1914, and composite rose for the whole period of observation.]

CLOUD

The greater strength of the afternoon wind would lead us to suppose that
the cloudiness, which in the trade-wind belt, is to so great an extent
dependent on the wind, is greatest in the afternoon. The diagrams bring
out this fact. Barely is the sky quite clear after the noon hour. Still
more striking is the contrast between the morning and afternoon if we
combine the two densest shadings of the figures. Light, high-lying
cirrus clouds are most characteristic of early morning hours. They
produce some very striking sky effects just before sunrise as they catch
the sun’s rays aloft. An hour or two after sunrise they disappear and
small cumulus clouds begin to form. These grow rapidly as the winds
begin and by afternoon become bulky and numerous. In the wet season they
grow into the nimbus and stratus types that precede a sudden downpour of
water or a furious hailstorm. This is best seen from the base of a
mountain range looking towards the crest, where the cloud-and
rain-making processes of this type are most active.

CLOUD ANALYSIS, SANTA LUCIA

--------------+---------+---------+---------+---------+---------++---------+
| Nov. | Dec. | Jan. | Feb. | March || Total |
Type of cloud |a.m. p.m.|a.m. p.m.|a.m. p.m.|a.m. p.m.|a.m. p.m.||a.m. p.m.|
--------------+---------+---------+---------+---------+---------++---------+
Cirrus | 6 2 | 15 2 | 9 2 | 5 3 | 6 3 || 41 12 |
Cirro-stratus | -- -- | -- -- | -- -- | -- -- | -- -- || -- -- |
Cirro-cumulus | 4 4 | 7 11 | 3 5 | 6 8 | 17 10 || 37 38 |
Cumulus | 3 4 | 4 7 | 10 9 | 15 13 | 5 13 || 37 46 |
Strato-cumulus| 2 6 | 3 10 | 7 14 | 2 3 | -- 3 || 14 36 |
Stratus | -- -- | -- 1 | -- -- | -- 1 | 1 2 || 2 4 |
Nimbus | -- -- | -- -- | -- -- | -- -- | -- -- || -- -- |
Clear | -- -- | 2 -- | 2 1 | -- -- | 2 -- || 6 1 |
--------------+---------+---------+---------+---------+---------++---------+

UNUSUAL WEATHER PHENOMENA, SANTA LUCIA, 1913-14

[Illustration: Fig. 105--Monthly cloudiness of Santa Lucia from January
to July, 1914. Mean cloudiness for the whole period is also shown.]

The following abstracts are selected because they give some important
features of the weather not included in the preceding tables and graphs.
Of special interest are the strong contrasts between the comparatively
high temperatures of midday and the sudden “tempests” accompanied by
rain or hail that follow the strong convectional movements dependent
upon rapid and unequal heating. The furious winds drive the particles of
hail like shot. It is sometimes impossible to face them and the pack
train must be halted until the storm has passed. Frequently they leave
the ground white with hailstones. We encountered one after another of
these “tempestades” on the divide between Lambrama and Antabamba in
1911. They are among the most impetuous little storms I have ever
experienced. The longest of them raged on the divide from two-o’clock
until dark, though in the valleys the sun was shining. Fortunately, in
this latitude they do not turn into heavy snowstorms as in the
Cordillera of northwestern Argentina, where the passes are now and then
blocked for weeks at a time and loss of human life is no infrequent
occurrence.[35] They do, however, drive the shepherds down from the
highest slopes to the mid-valley pastures and make travel uncomfortable
if not unsafe.

ABSTRACT FROM DAILY WEATHER OBSERVATIONS, SANTA LUCIA, 1913-14

NOVEMBER

“Tempest” recorded 11 times, distant thunder and lightning 9 times.
Unusual weather records: “clear sky, scorching sun, good weather”
(Nov. 29); “morning sky without a single cloud, weather agreeable”
(Nov. 30).

DECEMBER

Clear morning sky 6 times. Starry night or part of night 7 times.
Beginning of rain and strong wind frequently observed at 5-6 P.M.
“Tempest” mentioned 19 times--5 times at midnight, 8 times at 5-6
P.M.

JANUARY

Clear morning sky 5 times. Starry night 3 times. Rain, actual or
threatening, characteristic of afternoons. “Tempest,” generally
about 5-6 P.M., 7 times. Sun described 4 times as scorching and,
when without wind, heat as stifling. Weather once “agreeable.”

FEBRUARY

Constant cloud changes, frequent afternoon or evening rains.
“Tempest,” generally 4 P.M. and later, 16 times.

MARCH

Twice clear morning skies, once starry night. Scorching sun and
stifling heat on one occasion. “Tempest,” generally in late
afternoon and accompanied by hail, 19 times. Observed 3 or 4 times
a strong, “land breeze” (terral) of short duration (15-20 mins.)
and at midnight.

MOROCOCHA

Morococha, in the Department of Ancachs, Peru, lies in 76° 11′ west
longitude and 11° 45′ south latitude and immediately east of the crest
line of the Maritime Cordillera. It is 14,300 feet above sea level, and
is surrounded by mountains that extend from 1,000 to 3,000 feet higher.
The weather records are of special interest in comparison with those of
Santa Lucia. Topographically the situations of the two stations are
closely similar hence we may look for climatic differences dependent on
the latitudinal difference. This is shown in the heavier rainfall of
Morococha, 4° nearer the equatorial climatic zone. (For location see
Fig. 66.)

The meteorological data for 1908-09 were obtained from records kept by
the Morococha Mining Company for use in a projected hydro-electric
installation. Other data covering the years 1906-11 have appeared in the
bulletins of the _Sociedad Geográfica de Lima_. These are not complete
but they have supplied rainfall data for the years 1910-11;[36] those
for 1906 and 1907 have been obtained from the _Boletín de Minas_.[37]

TEMPERATURE

The most striking facts expressed by the various temperature curves are
the shortness of the true winter season--its restriction to June and
July--and its abrupt beginning and end. This is well known to anyone who
has lived from April to October or November at high elevations in the
Central Andes. Winter comes on suddenly and with surprising regularity
from year to year during the last few days of May and early June. In the
last week of July or the first week of August the temperatures make an
equally sudden rise. During 1908 and 1909 the mean temperature reached
the freezing point but once each year--July 24 and July 12
respectively. The absolute minimum for the two years was -22° C. July of
1908 and June of 1909 are also the months of smallest diurnal
variability, showing that the winter temperatures are maintained with
great regularity. Like all tropical high-level stations, Morococha
exhibits winter maxima that are very high as compared with the winter
maxima of the temperate zone. In both June and July of 1908 and 1909 the
maximum was maintained for about a week above 55° F. (12.8° C.), and in
1909 above 60° F. (15.6° C.), the mean maximum for the year being only
4.7° F. higher. For equal periods, however, the maxima fell to levels
about 10° F. below those for the period from December to May, 1908.

It is noteworthy that the lowest maximum for 1909 was in October, 44° F.
(6.7° C.); and that other low maxima but little above those of June and
July occur in almost all the other months of the year. While 1909 was in
this respect an exceptional year, it nevertheless illustrates a fact
that may occur in any month of any year. Its occurrence is generally
associated with cloudiness. One of the best examples of this is found in
the January maximum curve for 1909, where in a few days the maxima fell
12° F. Cloud records are absent, hence a direct comparison cannot be
made, but a comparison of the maximum temperature curve with the graphic
representation of mean monthly rainfall, will emphasize this relation of
temperature and cloudiness. February was the wettest month of both 1908
and 1909. In sympathy with this is the large and sharp drop from the
January level of the maxima--the highest for the year--to the February
level. The mean temperatures are affected to a less degree because the
cloudiness retards night radiation of heat, thus elevating the maxima.
Thus in 1908 the lowest minimum for both January and February was 28.4°
F. (-2° C.). For 1909 the minima for January and February were 27.5° F.
(-2.5° C.) and 29.3° F. (-1.5° C.) respectively.

[Illustration: FIG. 106 A--DIURNAL TEMPERATURE, MOROCOCHA, 1908

B--DIURNAL TEMPERATURE, MOROCOCHA, 1909

D--DIURNAL RANGE OF TEMPERATURE, MOROCOCHA, 1908

E--DIURNAL RANGE OF TEMPERATURE, MOROCOCHA, 1909

G--DIURNAL VARIABILITY OF TEMPERATURE, MOROCOCHA, 1908

H--DIURNAL VARIABILITY OF TEMPERATURE, MOROCOCHA, 1909

C--MEAN MONTHLY TEMPERATURE, MOROCOCHA

F--MONTHLY MEANS OF DIURNAL RANGE OF TEMPERATURE, MOROCOCHA]

The extent to which high minima may hold up the mean temperature is
shown by the fact that the mean monthly temperature for January, 1908,
was lower than for February. Single instances illustrate this relation
equally well. For example, on March 5th, 1908, there occurred the
heaviest rainfall of that year. The maximum and minimum curves almost
touch. The middle of April and late September, 1909, are other
illustrations. The relationship is so striking that I have put the two
curves side by side and have had them drawn to the same scale.

FREQUENCY OF THE DIURNAL VARIABILITY, MOROCOCHA, 1908 AND 1909

1908
-----------------------------------------------------------------
Degrees | | | | | | | | | | | | |Total No.
F. | J.| F.| M.| A.| M.| J.| J.| A.| S.| O.| N.| D.| of days
--------+---+---+---+---+---+---+---+---+---+---+---+---+---------
0 | --| 3 | 2 | 3 | --| --| 2 | 1 | 3 | 1 | 1 | 3 | 19
0-1 | 6 | 5 | 6 |10 | 9 |10 |13 |10 | 8 | 6 | 6 | 5 | 94
1-2 | 4 | 1 | 3 | 7 | 5 | 3 | 7 | 7 | 8 | 6 | 6 | 4 | 61
2-3 | 6 | 1 | 3 | 4 | 9 | 2 | 2 | 4 | 4 | 7 | 7 | 4 | 53
3-4 | 5 | 3 | 2 | 3 | 3 | 4 | 2 | 9 | 4 | 5 | 3 | 5 | 48
4-5 | 2 | 3 | 1 | 1 | 2 | 5 | 5 | --| 1 | 1 | 6 | 3 | 30
Over 5 | 3 | 4 | 3 | 2 | 3 | 6 | --| --| 2 | 5 | 1 | 5 | 34
--------+---+---+---+---+---+---+---+---+---+---+---+---+---------
Days per|26 |20 |20 |30 |31 |30 |31 |31 |30 |31 |30 |20 | 339
month | | | | | | | | | | | | |
------------------------------------------------------------------
1909
---------------------------------------------------------------------
| | | | | | | | | | | | | |Mean
Degrees | | | | | | | | | | | | |Total |for
F. | J.| F.| M.| A.| M.| J.| J.| A.| S.| O.| N.| D.|No. of|1908
| | | | | | | | | | | | | days |-1909
--------+---+---+---+---+---+---+---+---+---+---+---+---+------+-----
0 | 6 | 1 | 4 | 2 | 1 | 2 | 4 | 4 | 3 | 6 | 2 | 1 | 36 | 27.5
0-1 | 9 | 8 | 5 | 6 | 6 | 7 | 8 |13 | 9 | 4 |11 |10 | 96 | 95
1-2 | 4 | 6 | 8 | 3 |11 |14 | 3 | 3 | 5 | 3 | 9 | 6 | 75 | 68
2-3 | 3 | 7 | 4 | 8 | 4 | 3 | 6 | 6 | 4 | 6 | 1 | 3 | 55 | 54
3-4 | 4 | 5 | 3 | 6 | 4 | 4 | 4 | 3 | 6 | 3 | 2 | 5 | 49 | 48.5
4-5 | 1 | 1 | 5 | 1 | 2 | --| 2 | 1 | 1 | 2 | --| 2 | 18 | 24
Over 5 | 4 | --| 2 | 4 | 3 | --| 4 | 1 | 2 | 7 | 5 | 3 | 35 | 34.5
--------+---+---+---+---+---+---+---+---+---+---+---+---+------+-----
Days per|31 |28 |31 |30 |31 |30 |31 |31 |30 |31 |30 |30 | 364 |351.5
month | | | | | | | | | | | | | |
---------------------------------------------------------------------

RAINFALL

The annual rainfall of Morococha is as follows:

1906 28 inches ( 712 mm.)
1907 40 " (1,011 mm.)[38]
1908 57 " (1,450 mm.)
1909 45 " (1,156 mm.)
1910 47 " (1,195 mm.)
1911 25 " ( 622 mm.)

[Illustration: FIG. 107A.]

[Illustration: FIG. 107B.]

[Illustration: FIG. 107C.]

[Illustration: Fig. 107--Rainfall of Morococha. Fig. 107A shows daily
rainfall during the rainy (summer) season, 1908-1909. Fig. 107B shows
monthly rainfall from July, 1905, to December, 1911, and Fig. 107C the
annual and mean rainfall for the same period.]

The mean for the above six years amounts to 40 inches (1,024 mm.). This
is a value considerably higher than that for Caylloma or Santa Lucia.
The greater rainfall of Morococha is probably due in part to its more
northerly situation. An abnormal feature of the rainfall of 1908, the
rainiest year, is the large amount that fell in June. Ordinarily June
and July, the coldest months, are nearly or quite rainless. The normal
concurrence of highest temperatures and greatest precipitation is of
course highly favorable to the plant life of these great altitudes. Full
advantage can be taken of the low summer temperatures if the growing
temperatures are concentrated and are accompanied by abundant rains.
Since low temperatures mean physiologic dryness, whether or not rains
are abundant, the dryness of the winter months has little effect in
restricting the range of Alpine species.

The seasonal distribution of rain helps the plateau people as well as
the plateau plants. The transportation methods are primitive and the
trails mere tracks that follow the natural lines of topography and
drainage. Coca is widely distributed, likewise corn and barley which
grow at higher elevations, and wool must be carried down to the markets
from high-level pastures. In the season of rains the trails are
excessively wet and slippery, the streams are often in flood and the
rains frequent and prolonged. On the other hand the insignificant
showers of the dry or non-growing season permit the various products to
be exchanged over dry trails.

The activities of the plateau people have had a seasonal expression from
early times. Inca chronology counted the beginning of the year from the
middle of May, that is when the dry season was well started and it was
inaugurated with the festivals of the Sun. With the exception of June
when the people were entirely busied in the irrigation of their fields,
each month had its appropriate feasts until January, during which month
and February and March no feasts were held. April, the harvest month,
marked the recommencement of ceremonial observances and a revival of
social life.[39]

In Spanish times the ritualistic festivals, incorporated with fairs,
followed the seasonal movement. Today progress in transportation has
caused the decadence of many of the fairs but others still survive. Thus
two of the most famous fairs of the last century, those of Vilque
(province of Puno) and Yunguyo (province of Chucuito), were held at the
end of May and the middle of August respectively. Copacavana, the famous
shrine on the shores of Titicaca, still has a well-attended August fair
and Huari, in the heart of the Bolivian plateau, has an Easter fair
celebrated throughout the Andes.

COCHABAMBA

Cochabamba, Bolivia, lies 8,000 feet above sea level in a broad basin in
the Eastern Andes. The Cerro de Tunari, on the northwest, has a snow and
ice cover for part of the year. The tropical forests lie only a single
long day’s journey to the northeast. Yet the basin is dry on account of
an eastern front range that keeps out the rain-bearing trade winds. The
Rio Grande has here cut a deep valley by a roundabout course from the
mountains to the plains so that access to the region is over bordering
elevations. The basin is chiefly of structural origin.

The weather records from Cochabamba are very important. I could obtain
none but temperature data and they are complete for 1906 only. Data for
1882-85 were secured by von Boeck[40] and they have been quoted by
Sievers and Hann. The mean annual temperature for 1906 was 61.9° F.
(16.6° C.), a figure in close agreement with von Boeck’s mean of 60.8°
F. (16° C.). The monthly means indicate a level of temperature favorable
to agriculture. The basin is in fact the most fertile and highly
cultivated area of its kind in Bolivia. Bananas, as well as many other
tropical and subtropical plants, grow in the central plaza. The nights
of midwinter are uncomfortably cool; and the days of midsummer are
uncomfortably hot but otherwise the temperatures are delightful. The
absolute extremes for 1906 were 81.5° F. (27.5° C.) on December 11, and
39.9° F. (4.4° C.) on July 15 and 16. The (uncorrected) readings of von
Boeck give a greater range. High minima rather than high maxima
characterize the summer. The curve for 1906 shows the maxima for June
and July cut off strikingly by an abrupt drop of the temperature and
indicates a rather close restriction of the depth of the season to these
two months, which are also those of greatest diurnal range.

[Illustration: FIG. 108 A--DIURNAL TEMPERATURE, COCHABAMBA, 1906

B--DIURNAL TEMPERATURE, COCHABARMBA, 1907

E--DIURNAL RANGE OF TEMPERATURE, COCHABARMBA, 1907

D--DIURNAL RANGE OF TEMPERATURE, COCHABARMBA, 1906

G--DIURNAL VARIABILITY, COCHABARMBA, 1906

H--DIURNAL VARIABILITY, COCHABAMBA, 1907

C--MEAN MONTHLY TEMPERATURES, COCHABAMBA

F--MONTHLY MEANS OF DIURNAL RANGE, COCHABAMBA]

The rainfall of about 18 inches is concentrated in the summer season, 85
per cent falling between November and March. During this time the town
is somewhat isolated by swollen streams and washed out trails: hence
here, as on the plateau, there is a distinct seasonal distribution of
the work of planting, harvesting, moving goods, and even mining, and of
the general commerce of the towns. There is an approach to our winter
season in this respect and in respect of a respite from the almost
continuously high temperatures of summer. The daytime temperatures of
summer are however mitigated by the drainage of cool air from the
surrounding highlands. This, indeed, prolongs the period required for
the maturing of plants, but there are no harmful results because
freezing temperatures are not reached, even in winter.

MONTHLY TEMPERATURES, COCHABAMBA, 1906

-------------+-------------+-------------+-------------+--------------
Month | Mean Min. | Mean Max. | Mean Range | Daily Mean
-------------+-------------+-------------+-------------+--------------
January | 55.7 | 72.25 | 16.65 | 63.3
February | 61.2 | 71.3 | 10.1 | 65.5
March | 59.8 | 72.6 | 12.8 | 65.5
April | 55.06 | 70.8 | 15.74 | 62.2
May | 50.9 | 68.7 | 17.8 | 59.1
June | 47.1 | 65.6 | 18.5 | 55.6
July | 44.8 | 64.9 | 20.1 | 54.1
August | 49.9 | 68.0 | 18.1 | 58.2
September | 55.6 | 73.2 | 17.6 | 63.7
October | 56.1 | 73.4 | 17.3 | 64.0
November | 58.1 | 75.7 | 17.6 | 66.2
December | 58.6 | 73.9 | 15.3 | 65.8
-------------+-------------+-------------+-------------+--------------

[Illustration: FIGS. 109-113--Temperature curves for locations in the
montaña, July and August, 1911. The curves are based on hourly readings
with interpolated readings for such critical occurrences as the
appearance of cloud or rain. Dry bulb readings are shown by solid lines,
wet bulb by dotted lines, and breaks in the continuity of the
observations by heavy broken lines. Fig. 109 is for Pongo de Mainique,
August 20 and 21; Fig. 110 for Yavero; Fig. 111 for Santo Anato, August
11 and 12; Fig. 112 for Sahuayaco, August 20, and Fig. 113 for Santa
Ana, July 30 to August 1.]

[Illustration: FIG. 114--Typical afternoon cloud composition at Santa
Ana during the dry season.]

[Illustration: FIG. 115--Temperature curve for Abancay drawn from data
obtained by hourly readings on September 27, 1911. Dry bulb readings are
shown by a heavy solid line, wet bulb readings by a dotted line. The
heavy broken line shows the normal curve when the sky is unobscured by
cloud. The reduction in temperature with cloud is very marked.]

FREQUENCY OF DIURNAL VARIABILITY AT COCHABAMBA, 1906

-------+----+----+----+----+----+----+----+----+----+----+----+----++------
| | | | | | | | | | | | ||Total
Degrees| | | | | | | | | | | | ||No. of
F. | J. | F. | M. | A. | M. | J. | J. | A. | S. | O. | N. | D. || days
-------+----+----+----+----+----+----+----+----+----+----+----+----++------
0 | 1 | 3 | 10 | 12 | 6 | 10 | 9 | 6 | 9 | 6 | 3 | 4 || 79
0-1 | 5 | -- | 3 | 5 | 3 | 3 | -- | 4 | -- | 3 | 1 | 1 || 28
1-2 | 10 | 10 | 13 | 11 | 15 | 7 | 14 | 11 | 15 | 10 | 14 | 13 || 143
2-3 | 7 | 11 | 3 | 1 | 5 | 8 | 7 | 4 | 3 | 6 | 7 | 6 || 68
3-4 | 6 | 2 | 2 | 1 | 2 | 2 | 1 | 6 | 3 | 4 | 3 | 5 || 37
4-5 | -- | -- | -- | -- | -- | -- | -- | -- | -- | 1 | 1 | 1 || 3
Over 5 | 2 | 2 | -- | -- | -- | -- | -- | -- | -- | 1 | 1 | 1 || 7
-------+----+----+----+----+----+----+----+----+----+----+----+----++------

A series of curves shows the daily march of temperature at various
locations along the seventy-third meridian. Figs. 109 to 113 are for the
Urubamba Valley. Respectively they relate to Pongo de Mainique, 1,200
feet elevation (365 m.), the gateway to the eastern plains; Yavero,
1,600 feet (488 m.), where the tributary of this name enters the main
stream; Santo Anato, 1,900 feet (580 m.); Sahuayaco, 2,400 feet (731
m.), and Santa Ana, 3,400 feet (1,036 m.), one of the outposts of
civilization beyond the Eastern Cordillera. The meteorological
conditions shown are all on the same order. They are typical of dry
season weather on the dry floor of a montaña valley. The smooth curves
of clear days are marked by high mid-day temperatures and great diurnal
range. Santo Anato is a particularly good illustration: the range for
the 24 hours is 38° F. (21.1° C.). This site, too, is remarkable as one
of the most unhealthful of the entire valley. The walls of the valley
here make a sharp turn and free ventilation of the valley is obstructed.
During the wet season tertian fever prevails to a degree little known
east of the Cordillera, though notorious enough in the deep valleys of
the plateau. The curves show relative humidity falling to a very low
minimum on clear days. At Santo Anato and Santa Ana, for example, it
drops below 30 per cent during the heat of the day. Afternoon
cloudiness, however, is a common feature even of the dry season. A
typical afternoon cloud formation is shown in Fig. 114. The effect on
temperature is most marked. It is well shown in the curve for August 20
and 22 at Yavero. Cloudiness and precipitation increase during the
summer months. At Santa Ana the rainfall for the year 1894-95 amounted
to 50 inches, of which 60 per cent fell between December and March. For
a discussion of topographic features that have some highly interesting
climatic effects in the eastern valleys of Peru see Chapter VI.

[Illustration: FIGS. 116-118--Temperature curves for locations in the
Maritime Cordillera and its western valleys, October, 1911. For
construction of curves see Figs. 109-113. Fig. 116 is for Camp 13 on the
northern slope of the Maritime Cordillera (which here runs from east to
west), October 13-15; Fig. 117 for Cotahuasi, October 26; Fig. 118 for
Salamanca, October 31.]

[Illustration: FIG. 119.

FIG. 120.

FIGS. 119-120--Temperature curves for the Coast Desert, November, 1911.
Fig. 119 is for Aplao, November 4 and 5; and Fig. 120 for Camaná,
November 9 and 10. For construction of curves see Figs. 109 to 113.]

Abancay, 8,000 feet (2,440 m.), in one of the inter-Andean basins, is
situated in the zone of marked seasonal precipitation. The single day’s
record shows the characteristic effect of cloud reducing the maximum
temperature of the day and maintaining the relative humidity.

Camp 13, 15,400 feet (4,720 m.), lies near the crest of the Maritime
Cordillera a little south of Antabamba. Afternoon storms are one of its
most significant features. Cotahuasi, 9,100 feet (2,775 m.) is near the
head of a west-coast valley. Its low humidity is worthy of note. That
for Salamanca, 12,700 feet (3,870 m.), is similar but not so marked.

Aplao, 3,100 feet (945 m.), and Camaná at the seacoast are stations in
the west-coast desert. The interior location of the former gives it a
greater range of temperature than Camaná, yet even here the range is
small in comparison with the diurnal extremes of the montaña, and the
tempering effect of the sea-breeze is clearly apparent. Camaná shows a
diurnal temperature range of under 10° F. and also the high relative
humidity, over 70 per cent, characteristic of the coast.

PART II

PHYSIOGRAPHY OF THE PERUVIAN ANDES

CHAPTER XI

THE PERUVIAN LANDSCAPE

From the west coast the great Andean Cordillera appears to have little
of the regularity suggested by our relief maps. Steep and high cliffs in
many places form the border of the land and obstruct the view; beyond
them appear distant summits rising into the zone of clouds. Where the
cliffs are absent or low, one may look across a sun-baked, yellow
landscape, generally broken by irregular foothills that in turn merge
into the massive outer spurs and ranges of the mountain zone. The plain
is interrupted by widely separated valleys whose green lowland meadows
form a brilliant contrast to the monotonous browns and yellows of the
shimmering desert. In rare situations the valley trenches enable one to
look far into the Cordillera and to catch memorable glimpses of lofty
peaks capped with snow.

If the traveler come to the west-coast landscape from the well-molded
English hills or the subdued mountains of Vermont and New Hampshire with
their artistic blending of moderate profiles, he will at first see
nothing but disorder. The scenery will be impressive and, in places,
extraordinary, but it is apparently composed of elements of the greatest
diversity. All the conceivable variations of form and color are
expressed, with a predominance of bold rugged aspects that give a
majestic appearance to the mountain-bordered shore. One looks in vain
for some sign of a quiet view, for some uniformity of features, for some
landscape that will remind him of the familiar hills of home. The Andes
are aggressive mountains that front the sea in formidable spurs or
desert ranges. Could we see in one view their entire elevation from
depths of over 20,000 feet beneath sea level to snowy summits, a total
altitude of 40,000 feet (12,200 m.), their excessive boldness would be
more apparent. No other mountains in the world are at once so
continuously lofty and so near a coast which drops off to abyssal
depths.

The view from the shore is, however, but one of many which the Andes
exhibit. Seen from the base the towering ranges display a stern aspect,
but, like all mountains, their highest slopes and spurs must be crossed
and re-crossed before the student is aware of other aspects of a quite
different nature. The Andes must be observed from at least three
situations: from the floors of the deep intermontane valleys, from the
intermediate slopes and summits, and from the uppermost levels as along
the range crests and the highest passes. Strangely enough it is in the
summit views that one sees the softest forms. At elevations of 14,000 to
16,000 feet (4,270 to 4,880 m.), where one would expect rugged spurs,
serrate chains, and sharp needles and horns, one comes frequently upon
slopes as well graded as those of a city park--grass-covered,
waste-cloaked, and with gentle declivity (Figs. 121-124).

The graded, waste-cloaked slopes of the higher levels are interpreted as
the result of prolonged denudation in an erosion cycle which persisted
through the greater part of the Tertiary period, and which was closed by
uplifts aggregating at least several thousands of feet. Above the level
of the mature slopes rise the ragged profiles and steep, naked
declivities of the snow-capped mountains which bear residual relations
to the softer forms at their bases. They are formed upon rock masses of
greater original elevation and of higher resistance to denudation.
Though they are dominating topographic features, they are much less
extensive and significant than the tame landscape which they surmount.

[Illustration: FIG. 121--Looking north from the hill near Anta in the
Anta basin north of Cuzco. Typical composition of slopes and intermont
basins in the Central Andes. Alluvial fill in the foreground; mature
slopes in the background; in the extreme background the snow-capped
crests of the Cordillera Vilcapampa.]

[Illustration: FIG. 122--Showing topographic conditions before the
formation of the deep canyons in the Maritime Cordillera. The view,
looking across a tributary canyon of the Antabamba river, shows in the
background the main canyon above Huadquirca. Compare with Fig. 60.]

Below the level of the mature slopes are topographic features of equal
prominence: gorges and canyons up to 7,000 feet deep. The deeply
intrenched streams are broken by waterfalls and almost continuous
rapids, the valley walls are so abrupt that one may, in places, roll
stones down a 4,000 foot incline to the river bed, and the tortuous
trail now follows a stream in the depths of a profound abyss, now scales
the walls of a labyrinthine canyon.

[Illustration: FIG. 123--Mature slopes between Ollantaytambo and
Urubamba.]

[Illustration: FIG. 124--Dissected mature slopes north of Anta in the
Anta basin north of Cuzco.]

[Illustration: FIG. 125--Mature upper and young lower slopes at the
outlet of the Cuzco basin.]

The most striking elements of scenery are not commonly the most
important in physiography. The oldest and most significant surface may
be at the top of the country, where it is not seen by the traveler or
where it cannot impress him, except in contrast to features of greater
height or color. The layman frequently seizes on a piece of bad-land
erosion or an outcrop of bright-colored sandstone or a cliff of
variegated clays or a snow-covered mountain as of most interest. All we
can see of a beautiful snow-clad peak is mere entertainment compared
with what subdued waste-cloaked hill-slopes may show. We do not wish to
imply that everywhere the tops of the Andes are meadows, that there are
no great scenic features in the Peruvian mountains, or that they are not
worth while. But we do wish to say that the bold features are far less
important in the interpretation of the landscape.

Amid all the variable forms of the Peruvian Cordillera certain strongly
developed types recur persistently. That their importance and relation
may be appreciated we shall at once name them categorically and
represent them in the form of a block diagram (Fig. 126). The principal
topographic types are as follows:

1. An extensive system of high-level, well-graded, mature slopes,
below which are:

2. Deep canyons with steep, and in places, cliffed sides and narrow
floors, and above which are:

3. Lofty residual mountains composed of resistant, highly deformed
rock, now sculptured into a maze of serrate ridges and sharp
commanding peaks.

4. Among the forms of high importance, yet causally unrelated to
the other closely associated types, are the volcanic cones and
plateaus of the western Cordillera.

5. At the valley heads are a full complement of glacial features,
such as cirques, hanging valleys, reversed slopes, terminal
moraines, and valley trains.

6. Finally there is in all the valley bottoms a deep alluvial fill
formed during the glacial period and now in process of dissection.

Though there are in many places special features either remotely related
or quite unrelated to the principal enumerated types, they belong to the
class of minor forms to which relatively small attention will be paid,
since they are in general of small extent and of purely local interest.

[Illustration: FIG. 126--Block diagram of the typical physiographic
features of the Peruvian Andes.]

The block diagram represents all of these features, though of necessity
somewhat more closely associated than they occur in nature. Reference to
the photographs, Figs. 121-124, will make it clear that the diagram is
somewhat ideal: on the other hand the photographs together include all
the features which the diagram displays. In descending from any of the
higher passes to the valley floor one passes in succession down a steep,
well-like cirque at a glaciated valley head, across a rocky terminal
moraine, then down a stair-like trail cut into the steep scarps which
everywhere mark the descent to the main valley floors, over one after
another of the confluent alluvial fans that together constitute a large
part of the valley fill, and finally down the steep sides of the inner
valley to the boulder-strewn bed of the ungraded river.

We shall now turn to each group of features for description and
explanation, selecting for first consideration the forms of widest
development and greatest significance--the high-level mature slopes
lying between the lofty mountains which rise above them and the deep,
steep-walled valleys sunk far below them. These are the great pasture
lands of the Cordillera; their higher portions constitute the typical
_puna_ of the Indian shepherds. In many sections it is possible to
pasture the vagrant flocks almost anywhere upon the graded slopes,
confident that the _ichu_, a tufted forage grass, will not fail and that
scattered brooks and springs will supply the necessary water. At
nightfall the flocks are driven down between the sheltering walls of a
canyon or in the lee of a cliff near the base of a mountain, or, failing
to reach either of these camps, the shepherd confines his charge within
the stone walls of an isolated corral.

In those places where the graded soil-covered slopes lie within the zone
of agriculture--below 14,000 feet--they are cultivated, and if the soil
be deep and fertile they are very intensively cultivated. Between Anta
and Urubamba, a day’s march north of Cuzco, the hill slopes are covered
with wheat and barley fields which extend right up to the summits (Fig.
134). In contrast are the uncultivated soil-less slopes of the mountains
and the bare valley walls of the deeply intrenched streams. The
distribution of the fields thus brings out strongly the principal
topographic relations. Where the softer slopes are at too high a level,
the climatic conditions are extreme and man is confined to the valley
floors and lower slopes where a laborious system of terracing is the
first requirement of agriculture.

The appearance of the country after the mature slopes had been formed is
brought out in Fig. 122. The camera is placed on the floor of a still
undissected, mature valley which shows in the foreground of the
photograph. In the middle distance is a valley whose great depth and
steepness are purposely hidden; beyond the valley are the smoothly
graded, catenary curves, and interlocking spurs of the mature upland. In
imagination one sees the valleys filled and the valley slopes confluent
on the former (now imaginary) valley floor which extends without
important change of expression to the border of the Cordillera. No
extensive cliffs occur on the restored surface, and none now occur on
large tracts of the still undissected upland. Since the mature slopes
represent a long period of weathering and erosion, their surfaces were
covered with a deep layer of soil. Where glaciation at the higher levels
and vigorous erosion along the canyons have taken place, the former soil
cover has been removed; elsewhere it is an important feature. Its
presence lends a marked softness and beauty to these lofty though
subdued landscapes.

The graded mountain slopes were not all developed (1) at the same
elevation, nor (2) upon rock of the same resistance to denudation, nor
(3) at the same distance from the major streams, nor (4) upon rock of
the same structure. It follows that they will not all display precisely
the same form. Upon the softer rocks at the lowest levels near the
largest streams the surface was worn down to extremely moderate slopes
with a local relief of not more than several hundred feet. Conversely,
there are quite unreduced portions whose irregularities have mountainous
proportions, and between these extremes are almost all possible
variations. Though the term _mature_ in a broad way expresses the stage
of development which the land had reached, _post mature_ should be
applied to those portions which suffered the maximum reduction and now
exhibit the softest profiles. At no place along the 73rd meridian was
denudation carried to the point of even local peneplanation. All of the
major and some of the minor divides bear residual elevations and even
approximately plane surfaces do not exist.

[Illustration: THE YALE PERUVIAN EXPEDITION OF 1911

HIRAM BINGHAM, DIRECTOR

COROPUNA QUADRANGLE

(_Cotahuasi_)]

Among the most important features of the mature slopes are (1) their
great areal extent--they are exhibited throughout the whole Central
Andes, (2) their persistent development upon rocks of whatever structure
or degree of hardness, and (3) their present great elevation in spite of
moderate grades indicative of their development at a much lower
altitude. Mature slopes of equivalent form are developed in widely
separated localities in the Central Andes: in every valley about
Cochabamba, Bolivia, at 10,000 feet (3,050 m.); at Crucero Alto in
southern Peru at 14,600 feet (4,450 m.); several hundred miles farther
north at Anta near Cuzco, 11,000 feet to 12,000 feet (3,600 to 3,940
m.), and Fig. 129 shows typical conditions in the Vilcabamba Valley
along the route of the Yale Peruvian Expedition of 1911. The
characteristic slopes so clearly represented in these four photographs
are the most persistent topographic elements in the physiography of the
Central Andes.

[Illustration: FIG. 127--Topographic profiles across typical valleys of
southern Peru. They are drawn to scale and the equality of gradient of
the gentler upper slopes is so close that almost any curve would serve
as a composite of the whole. These curves form the basis of the diagram,
Fig. 128, whereby the amount of elevation of the Andes in late geologic
time may be determined. The approximate locations of the profiles are as
follows: 1, Antabamba; 2, Chuquibambilla; 3, upland south of Antabamba;
4, Apurimac Canyon above Pasaje; 5, Abancay; 6, Arma (Cordillera
Vilcapampa); 7, divide above Huancarama; 8, Huascatay; 9, Huasentay,
farther downstream; 10, Rio Pampas. The upper valley in 8 is still
undissected; 7 is practically the same; 8a is at the level which 8 must
reach before its side slopes are as gentle as at the end of the
preceding interrupted cycle.]

The rock masses upon which the mature slopes were formed range from soft
to hard, from stratified shales, slates, sandstones, conglomerates, and
limestones to volcanics and intrusive granites. While these variations
impose corresponding differences of form, the graded quality of the
slopes is rarely absent. In some places the highly inclined strata are
shown thinly veiled with surface débris, yet so even as to appear
artificially graded. The rock in one place is hard granite, in another a
moderately hard series of lava flows, and again rather weak shales and
sandstones.

Proof of the rapid and great uplift of certain now lofty mountain ranges
in late geologic time is one of the largest contributions of
physiography to geologic history. Its validity now rests upon a large
body of diversified evidence. In 1907 I crossed the Cordillera Sillilica
of Bolivia and northern Chile and came upon clear evidences of recent
and great uplift. The conclusions presented at that time were tested in
the region studied in 1911, 500 miles farther north, with the result
that it is now possible to state more precisely the dates of origin of
certain prominent topographic forms, and to reconstruct the conditions
which existed before the last great uplift in which the Central Andes
were born. The relation to this general problem of the forms under
discussion will now be considered.

The gradients of the mature slopes, as we have already seen, are
distinctly moderate. In the Anta region, over an area several hundred
square miles in extent, they run from several degrees to 20° or 30°.
Ten-degree slopes are perhaps most common. If the now dissected slopes
be reconstructed on the basis of many clinometer readings, photographs,
and topographic maps, the result is a series of profiles as in Fig. 127.
If, further, the restored slopes be coördinated over an extensive area
the gradients of the resulting valley floors will run from 3° to 10°.
Finally, if these valley floors be extended westward to the Pacific and
eastward to the Amazon basin, they will be found about 5,000 feet above
sea level and 4,000 feet above the eastern plains. (For explanation of
method and data employed, see the accompanying figures 127-128). It is,
therefore, a justifiable conclusion that since the formation of the
slopes the Andes have been uplifted at least a mile, or, to put it in
another way, the Andes at the time of formation of the mature slopes
were at least a mile lower than they are at present.

[Illustration: FIG. 128--Composition of slopes and profiles in the
Peruvian Andes. By superimposing the cross profiles of typical valleys
as shown in Fig. 127 a restoration is possible of the longitudinal
profiles of the earlier cycle of erosion. The difference in elevation of
the two profiles gives less than the minimum amount of uplift that must
have occurred. Case A represents a valley in which recent cutting has
not yet reached the valley head. Below the point 1 the profile has been
steepened and lowered by erosion in the current cycle. Above point 1 the
profile is still in the stage it reached in the preceding cycle. In case
B the renewed erosion of the current cycle has reached to the valley
head. Case C represents conditions similar to those in the preceding
cases save that the stream is typical of those that lie nearest the
steep flexed or faulted margins of the Cordillera and discharge to the
low levels of the desert pampa on the west or the tropical plains on the
east.]

Further proof of recent and great uplift is afforded by the deeply
intrenched streams. After descending the long graded slopes one comes
upon the cliffed canyons with a feeling of consternation. The effect of
powerful erosion, incident upon uplift, is heightened by the ungraded
character of the river bed. Falls and rapids abound, the river profiles
suggest tumultuous descents, and much time will elapse before the river
beds have the regular and moderate gradients of the streams draining the
mature surface before uplift as shown in the profiles by the dotted
lines representing the restored valley floors of the older cycle. Since
the smooth-contoured landscape was formed great changes have taken
place. The streams have changed from completely graded to almost
completely ungraded profiles; in place of a subdued landscape we now
have upland slopes intersected by mile-deep canyons; the high-level
slopes could not have been formed under existing conditions, for they
are being dissected by the present streams.

[Illustration: THE YALE PERUVIAN EXPEDITION OF 1911

HIRAM BINGHAM, DIRECTOR

COTAHUASI QUADRANGLE

(_La Cumbre_)]

Since the slopes of the land in general undergo progressive changes in
the direction of flatter gradients during a given geographical cycle, it
follows that with the termination of one cycle and the beginning of
another, two sets of slopes will exist and that the gradients of the two
will be unlike. The result is a break in the descent of the slopes from
high to low levels to which the name “topographic unconformity” is now
applied. It will be a prominent feature of the landscape if the higher,
older, and flatter gradients have but little declivity, and the
gradients of the lower younger slopes are very steep. In those places
where the relief of the first cycle was still great at the time of
uplift, the erosion forms of the second cycle may not be differentiated
from those of the first, since both are marked by steep gradients. In
the Central Andes the change in gradient between the higher and lower
slopes is generally well marked. It occurs at variable heights above
the valley floors, though rarely more than 3,000 feet above them. In the
more central tracts, far from the main streams and their associated
canyons, dissection in the present erosion cycle has not yet been
initiated, the mature slopes are still intact, and a topographic
unconformity has not yet been developed. The higher slopes are faced
with rock and topped with slowly moving waste. Ascent of the spur end is
by steep zigzag trails; once the top is gained the trail runs along the
gentler slopes without special difficulties.

It is worth noting at this point that the surface of erosion still older
than the mature slopes herewith described appears not to have been
developed along the seventy-third meridian of Peru, or if developed at
one time, fragments of it no longer remain. The last well-developed
remnant is southwest of Cuzco, Fig. 130. I have elsewhere described the
character and geographic distribution of this oldest recognizable
surface of the Central Andes.[41] Southern Peru and Bolivia and northern
Chile display its features in what seems an unmistakable manner. The
best locality yet found is in the Desaguadero Valley between Ancoaqui
and Concordia. There one may see thousands of feet of strongly inclined
sediments of varying resistance beveled by a well-developed surface of
erosion whose preserval is owing to a moderate rainfall and to location
in an interior basin.[42]

The highest surface of a region, if formed during a prolonged period of
erosion, becomes a surface of reference in the determination of the
character and amount of later crustal deformations, having somewhat the
same functions as a key bed in stratigraphic geology. Indeed, concrete
physiographic facts may be the _only_ basis for arguments as to both
epeirogenic and orogenic movements. The following considerations may
show in condensed form the relative value of physiographic evidence:

1. If movements in the earth’s crust are predominantly _downward_,
sedimentation may be carried on continuously, and a clear geologic
record may be made.

2. Even if crustal movements are alternately downward and upward,
satisfactory conclusions may be drawn from both (a) the nature of the
buried surfaces of erosion, and (b) the alternating character of the
sediments.

3. If, however, the deformative processes effect steady or intermittent
uplifts, there may be no sediments, at least within the limits of the
positive crustal units, and a geologic record must be derived not from
sedimentary deposits but from topographic forms. We speak of the _lost
intervals_ represented by stratigraphic breaks or unconformities and
commonly emphasize our ignorance concerning them. The longest, and, from
the human standpoint, the most important, break in the sedimentary
record is that of the present wherever degradation is the predominant
physiographic process. Unlike the others the _lost interval_ of the
present is not lost, if we may so put it, but is in our possession, and
may be definitely described as a concrete thing. It is the physiography
of today.

Even where long-buried surfaces of erosion are exposed to view, as in
northern Wisconsin, where the Pre-Cambrian paleo-plain projects from
beneath the Paleozoic sediments, or, as in New Jersey and southeastern
Pennsylvania, where the surface developed on the crystalline rocks
became by depression the floor of the Triassic and by more recent uplift
and erosion has been exposed to view,--even in such cases the exposures
are of small extent and give us at best but meager records. In short,
many of the breaks in the geologic record are of such long duration as
to make imperative the use of physiographic principles and methods. The
great Appalachian System of eastern North America has been a land area
practically since the end of the Paleozoic. In the Central Andes the
“lost interval,” from the standpoint of the sedimentary, record, dates
from the close of the Cretaceous, except in a few local intermont basins
partially filled with Tertiary or Pleistocene deposits. Physiographic
interpretations, therefore, serve the double purpose of supplying a part
of the geologic record while at the same time forming a basis for the
scientific study of the surface distribution of living forms.

The geologic dates of origin of the principal topographic forms of the
Central Andes may be determined with a fair degree of accuracy. Geologic
studies in Peru and Bolivia have emphasized the wide distribution of the
Cretaceous formations. They consist principally of thick limestones
above and sandstones and conglomerates below, and thus represent
extensive marine submergence of the earth’s crust in the Cretaceous
where now there are very lofty mountains. The Cretaceous deposits are
everywhere strongly deformed or uplifted to a great height, and all have
been deeply eroded. They were involved, together with other and much
older sediments, in the erosion cycle which resulted in the development
of the widely extended series of mature slopes already described. From
low scattered island elevations projecting above sea level, as in the
Cretaceous period, the Andes were transformed by compression and uplift
to a rugged mountain belt subjected to deep and powerful erosion. The
products of erosion were in part swept into the adjacent seas, in part
accumulated on the floors of intermont basins, as in the great interior
basins of Titicaca and Poopó.

Since the early Tertiary strata are themselves deformed from once simple
and approximately horizontal structures and subjected to moderate
tilting and faulting, it follows that mountain-making movements again
affected the region during later Tertiary. They did not, however,
produce extreme effects. They did stimulate erosion and bring about a
reorganization of all the slopes with respect to the new levels.

This agrees closely with a second line of evidence which rests upon an
independent basis. The alluvial fill which lies upon all the canyon and
valley floors is of glacial origin, as shown by its interlocking
relations with morainal deposits at the valley heads. It is now in
process of dissection and since its deposition in the Pleistocene had
been eroded on the average about 200 feet. Clearly, to form a 3,000-foot
canyon in hard rock requires much more time than to deposit and again
partially to excavate an alluvial fill several hundred feet deep.
Moreover, the glacial material is coarse throughout, and was built up
rapidly and dissected rapidly. In most cases, furthermore, coarse
material at the bottom of the glacial series rests directly upon the
rock of a narrow and ungraded valley floor. From these and allied facts
it is concluded that there is no long time interval represented by the
transitions from degrading to aggrading processes and back again. The
early Pleistocene, therefore, seems quite too short a period in which to
produce the bold forms and effect the deep erosion which marks the
period between the close of the mature cycle and the beginnings of
deposition in the Pleistocene.

The alternative conclusion is that the greater part of the canyon
cutting was effected in the late Tertiary, and that it continued into
the early Pleistocene until further erosion was halted by changed
climatic conditions and the augmented delivery of land waste to all the
streams. The final development of the well-graded high-level slopes is,
therefore, closely confined to a small portion of the Tertiary. The
closest estimate which the facts support appears to be Miocene or early
Pliocene. It is clear, however, that only the culmination of the period
can be definitely assigned. Erosion was in full progress at the close of
the Cretaceous and by middle Tertiary had effected vast changes in the
landscape. The Tertiary strata are marked by coarse basal deposit and by
thin and very fine top deposits. Though their deformed condition
indicates a period of crustal disturbance, the Tertiary beds give no
indication of wholesale transformations. They indicate chiefly tilting
and moderate and normal faulting. The previously developed effects of
erosion were, therefore, not radically modified. The surface was thus in
large measure prepared by erosion in the early Tertiary for its final
condition of maturity reached during the early Pliocene.

It seems appropriate, in concluding this chapter, to summarize in its
main outlines the physiography of southern Peru, partly to condense the
extended discussion of the preceding paragraphs, and partly to supply a
background for the three chapters that follow. The outstanding features
are broad plateau areas separated by well-defined “Cordilleras.” The
plateau divisions are not everywhere of the same origin. Those southwest
of Cuzco (Fig. 130), and in the Anta Basin (Fig. 124), northwest of
Cuzco, are due to prolonged erosion and may be defined as peneplane
surfaces uplifted to a great height. They are now bordered on the one
hand by deep valleys and troughs and basins of erosion and deformation;
and, on the other hand, by residual elevations that owe their present
topography to glacial erosion superimposed upon the normal erosion of
the peneplane cycle. The residuals form true mountain chains like the
Cordillera Vilcanota and Cordillera Vilcapampa; the depressions due to
erosion or deformation or both are either basins like those of Anta and
Cuzco or valleys of the canyon type like the Urubamba canyon; the
plateaus are broad rolling surfaces, the punas of the Peruvian Andes.

There are two other types of plateaus. The one represents a mature stage
in the erosion cycle instead of an ultimate stage; the other is volcanic
in origin. The former is best developed about Antabamba (Figs. 122 and
123), where again deep canyons and residual ranges form the borders of
the plateau remnants. The latter is well developed above Cotahuasi and
in its simplest form is represented in Fig. 133. Its surface is the top
of a vast accumulation of lavas in places over a mile thick. While rough
in detail it is astonishingly smooth in a broad view (Fig. 29). Above it
rise two types of elevations: first, isolated volcanic cones of great
extent surrounded by huge lava flows of considerable relief; and second,
discontinuous lines of peaks where volcanic cones of less extent are
crowded closely together. The former type is displayed on the Coropuna
Quadrangle, the latter on the Cotahuasi and La Cumbre Quadrangles.

So high is the elevation of the lava plateau, so porous its soil, so dry
the climate, that a few through-flowing streams gather the drainage of a
vast territory and, as in the Grand Canyon country of our West, they
have at long intervals cut profound canyons. The Arma has cut a deep
gorge at Salamanca; the Cotahuasi runs in a canyon in places 7,000 feet
deep; the Majes heads at the edge of the volcanic field in a steep
amphitheatre of majestic proportions.

Finally, we have the plateaus of the coastal zone. These are plains with
surfaces several thousand feet in elevation separated by gorges several
thousand feet deep. The Pampa de Sihuas is an illustration. The
post-maturely dissected Coast Range separates it from the sea. The
pampas are in general an aggradational product formed in a past age
before uplift initiated the present canyon cycle of erosion. Other
plateaus of the coastal zone are erosion surfaces. The Tablazo de Ica
appears to be of this type. That at Arica, Chile, near the southern
boundary of Peru, is demonstrably of this type with a border on which
marine planation has in places given rise to a broad terrace
effect.[43]

CHAPTER XII

THE WESTERN ANDES: THE MARITIME CORDILLERA OR CORDILLERA OCCIDENTAL

The Western or Maritime Cordillera of Peru forms part of the great
volcanic field of South America which extends from Argentina to Ecuador.
On the walls of the Cotahuasi Canyon (Fig. 131), there are exposed over
one hundred separate lava flows piled 7,000 feet deep. They overflowed a
mountainous relief, completely burying a limestone range from 2,000 to
4,000 feet high. Finally, upon the surface of the lava plateau new
mountains were formed, a belt of volcanoes 5,000 feet (1,520 m.) high
and from 15,000 to 20,000 feet (4,570 to 6,100 m.) above the sea. There
were vast mud flows, great showers of lapilli, dust, and ashes, and with
these violent disturbances also came many changes in the drainage. Sixty
miles northeast of Cotahuasi the outlet of an unnamed deep valley was
blocked, a lake was formed, and several hundred feet of sediments were
deposited. They are now wasting rapidly, for they lie in the zone of
alternate freezing and thawing, a thousand feet and more below the
snowline. Some of their bad-land forms look like the solid bastions of
an ancient fortress, while others have the delicate beauty of a Japanese
temple.

Not all the striking effects of vulcanism belong to the remote geologic
past. A day’s journey northeast of Huaynacotas are a group of lakes only
recently hemmed in by flows from the small craters thereabouts. The
fires in some volcanic craters of the Peruvian Andes are still active,
and there is no assurance that devastating flows may not again inundate
the valleys. In the great Pacific zone or girdle of volcanoes the
earth’s crust is yet so unstable that earthquakes occur every year, and
at intervals of a few years they have destructive force. Cotahuasi was
greatly damaged in 1912; Abancay is shaken every few years; and the
violent earthquakes of Cuzco and Arequipa are historic.

On the eastern margin of the volcanic country the flows thin out and
terminate on the summit of a limestone (Cretaceous) plateau. On the
western margin they descend steeply to the narrow west-coast desert. The
greater part of the lava dips beneath the desert deposits; there are a
few intercalated flows in the deposits themselves, and the youngest
flows--limited in number--have extended down over the inner edge of the
desert.

The immediate coast of southern Peru is not volcanic. It is composed of
a very hard and ancient granite-gneiss which forms a narrow coastal
range (Fig. 171). It has been subjected to very long and continued
erosion and now exhibits mature erosion forms of great uniformity of
profile and declivity.

From the outcrops of older rocks beneath the lavas it is possible to
restore in a measure the pre-volcanic topography of the Maritime
Cordillera, In its present altitude it ranges from several thousand to
15,000 feet above sea level. The unburied topography has been smoothed
out; the buried topography is rough (Figs. 29 and 166). The contact
lines between lavas and buried surfaces in the deep Majes and Cotahuasi
valleys are in places excessively serrate. From this, it seems safe to
conclude that the period of vulcanism was so prolonged that great
changes in the unburied relief were effected by the agents of erosion.
Thus, while the dominant process of volcanic upbuilding smoothed the
former rough topography of the Maritime Cordillera, erosion likewise
measurably smoothed the present high extra-volcanic relief in the
central and eastern sections. The effect has been to develop a broad and
sufficiently smooth aspect to the summit topography of the entire Andes
to give them a plateau character. Afterward the whole mountain region
was uplifted about a mile above its former level so that at present it
is also continuously lofty.

The zone of most intense volcanic action does not coincide with the
highest part of the pre-volcanic topography. If the pre-volcanic relief
were even in a very general way like that which would be exhibited if
the lavas were now removed, we should have to say that the chief
volcanic outbursts took place on the western flank of an old and deeply
dissected limestone range.

[Illustration: FIG. 129--Composition of slopes at Puquiura, Vilcabamba
Valley, elevation 9,000 feet (2,740 m.). The second prominent spur
entering the valley on the left has a flattish top unrelated to the rock
structure. Like the spurs on the right its blunt end and flat top
indicate an earlier erosion cycle at a lower elevation.]

[Illustration: FIG. 130--Inclined Paleozoic strata truncated by an
undulating surface of erosion at 15,000 feet, southwest of Cuzco.]

[Illustration: FIG. 131--Terraced valley slopes at Huaynacotas,
Cotahuasi Valley, at 11,500 feet (3,500 m.). Solimana is in the
background. On the floor of the Cotahuasi Canyon fruit trees grow. At
Huaynacotas corn and potatoes are the chief products. The section is
composed almost entirely of lava. There are over a hundred major flows
aggregating 5,000 to 7,000 feet thick.]

The volume of the lavas is enormous. They are a mile and a half thick,
nearly a hundred miles wide, and of indefinite extent north and south.
Their addition to the Andes, therefore, _has greatly broadened the zone
of lofty mountains_. Their passes are from 2,000 to 3,000 feet higher
than the passes of the eastern Andes. They have a much smaller number of
valleys sufficiently deep to enjoy a mild climate. Their soil is far
more porous and dry. Their vegetation is more scanty. They more than
double the difficulties of transportation. And, finally, their all but
unpopulated loftier expanses are a great vacant barrier between farms in
the warm valleys of eastern Peru and the ports on the west coast.

The upbuilding process was not, of course, continuous. There were at
times intervals of quiet, and some of them were long enough to enable
streams to become established. Buried valleys may be observed in a
number of places on the canyon walls, where subsequently lava flows
displaced the streams and initiated new drainage systems. In these quiet
intervals the weathering agents attacked the rock surfaces and formed
soil. There were at least three or four such prolonged periods of
weathering and erosion wherein a land surface was exposed for many
thousands of years, stream systems organized, and a cultivable soil
formed. No evidence has been found, however, that man was there to
cultivate the soil.

The older valleys cut in the quiet period are mere pygmies beside the
giant canyons of today. The present is the time of dominant erosion. The
forces of vulcanism are at last relatively quiet. Recent flows have
occurred, but they are limited in extent and in effects. They alter only
the minor details of topography and drainage. Were it not for the oases
set in the now deep-cut canyon floors, the lava plateau of the Maritime
Cordillera would probably be the greatest single tract of unoccupied
volcanic country in the world.

The lava plateau has been dissected to a variable degree. Its high
eastern margin is almost in its original condition. Its western margin
is only a hundred miles from the sea, so that the streams have steep
gradients. In addition, it is lofty enough to have a moderate rainfall.
It is, therefore, deeply and generally dissected. Within the borders of
the plateau the degree of dissection depends chiefly upon position with
respect to the large streams. These were in turn located in an
accidental manner. The repeated upbuilding of the surface by the
extensive outflow of liquid rock obliterated all traces of the earlier
drainage. In the Cotahuasi Canyon the existing stream, working down
through a mile of lavas, at last uncovered and cut straight across a
mountain spur 2,000 feet high. Its course is at right angles to that
pursued by the stream that once drained the spur. It is noteworthy that
the Cotahuasi and adjacent streams take northerly courses and join
Atlantic rivers. The older drainage was directly west to the Pacific.
Thus, vulcanism not only broadened the Andes and increased their height,
but also moved the continental divide still nearer the west coast.

The glacial features of the western or Maritime Cordillera are of small
extent, partly because vulcanism has added a considerable amount of
material in post-glacial time, partly because the climate is so
exceedingly dry that the snowline lies near the top of the country. The
slopes of the volcanic cones are for the most part deeply recessed on
the southern or shady sides. Above 17,500 feet (5,330 m.) the process of
snow and ice excavation still continues, but the tracts that exceed this
elevation are confined to the loftiest peaks or their immediate
neighborhood. There is a distinct difference between the glacial forms
of the eastern or moister and the western or dryer flanks of this
Cordillera. Only peaks like Coropuna and Solimana near the western
border now bear or ever bore snowfields and glaciers. By contrast the
eastern aspect is heavily glaciated. On La Cumbre Quadrangle, there is a
huge glacial trough at 16,000 feet (4,876 m.), and this extends with
ramifications up into the snowfields that formerly included the highest
country. Prolonged glacial erosion produced a full set of topographic
forms characteristic of the work of Alpine glaciers. Thus, each of the
main mountain chains that make up the Andean system has, like the system
as a whole, a relatively more-dry and a relatively less-dry aspect. The
snowline is, therefore, canted from west to east on each chain as well
as on the system. However, this effect is combined with a solar effect
in an unequal way. In the driest places the solar factor is the more
efficient and the snowline is there canted from north to south.

CHAPTER XIII

THE EASTERN ANDES: THE CORDILLERA VILCAPAMPA

The culminating range of the eastern Andes is the so-called Cordillera
Vilcapampa. Its numerous, sharp, snow-covered peaks are visible in every
summit view from the central portion of the Andean system almost to the
western border of the Amazon basin. Though the range forms a water
parting nearly five hundred miles long, it is crossed in several places
by large streams that flow through deep canyons bordered by precipitous
cliffs. The Urubamba between Torontoy and Colpani is the finest
illustration. For height and ruggedness the Vilcapampa mountains are
among the most noteworthy in Peru. Furthermore, they display glacial
features on a scale unequaled elsewhere in South America north of the
ice fields of Patagonia.

GLACIERS AND GLACIAL FORMS

One of the most impressive sights in South America is a tropical forest
growing upon a glacial moraine. In many places in eastern Bolivia and
Peru the glaciers of the Ice Age were from 5 to 10 miles long--almost
the size of the Mer de Glace or the famous Rhone glacier. In the Juntas
Valley in eastern Bolivia the tree line is at 10,000 feet (3,050 m.),
but the terminal moraines lie several thousand feet lower. In eastern
Peru the glaciers in many places extended down nearly to the tree line
and in a few places well below it. In the Cordillera Vilcapampa vast
snowfields and glacier systems were spread out over a summit area as
broad as the Southern Appalachians. The snowfields have since shrunk to
the higher mountain recesses; the glaciers have retreated for the most
part to the valley heads or the cirque floors; and the lower limit of
perpetual snow has been raised to 15,500 feet.

[Illustration: FIG. 132--Recessed volcanoes in the right background and
eroded tuffs, ash beds, and lava flows on the left. Maritime Cordillera
above Cotahuasi.]

[Illustration: FIG. 133--The summit of the great lava plateau above
Cotahuasi on the trail to Antabamba. The lavas are a mile and a half in
thickness. The elevation is 16,000 feet. Hence the volcanoes in the
background, 17,000 feet above sea level, are mere hills on the surface
of the lofty plateau.]

[Illustration: FIG. 134--Southwestern aspect of the Cordillera
Vilcapampa between Anta and Urubamba from Lake Huaipo. Rugged summit
topography in the background, graded post-mature slopes in the middle
distance, and solution lake in limestone in the foreground.]

[Illustration: FIG. 135--Summit view, Cordillera Vilcapampa. There are
fifteen glaciers represented in this photograph. The camera stands on
the summit of a minor divide in the zone of nivation.]

These features are surprising because neither Whymper[44] nor Wolf[45]
mentions the former greater extent of the ice on the volcanoes of
Ecuador, only ten or twelve degrees farther north. Moreover, Reiss[46]
denies that the hypothesis of universal climatic change is supported by
the facts of a limited glaciation in the High Andes of Ecuador; and J.
W. Gregory[47] completely overlooks published proof of the existence of
former more extensive glaciers elsewhere in the Andes:

“... the absence not only of any traces of former more extensive
glaciation from the tropics, as in the Andes and Kilimandjaro, but also
from the Cape.” He says further: “In spite of the extensive glaciers now
in existence on the higher peaks of the Andes, there is practically no
evidence of their former greater extension.”(!)

Whymper spent most of his time in exploring recent volcanoes or those
recently in eruption, hence did not have the most favorable
opportunities for gathering significant data. Reiss was carried off his
feet by the attractiveness of the hypothesis[48] relating to the effect
of glacial denudation on the elevation of the snowline. Gregory appeared
not to have recognized the work of Hettner on the Cordillera of Bogotá
and of Sievers[49] and Acosta on the Sierra Nevada de Santa Marta in
northern Colombia.

The importance of the glacial features of the Cordillera Vilcapampa
developed on a great scale in very low latitudes in the southern
hemisphere is twofold: first, it bears on the still unsettled problem of
the universality of a colder climate in the Pleistocene, and, second, it
supplies additional data on the relative depression of the snowline in
glacial times in the tropics. Snow-clad mountains near the equator are
really quite rare. Mount Kenia rising from a great jungle on the
equator, Kilimandjaro with its two peaks, Kibo and Mawenzi, two hundred
miles farther south, and Ingomwimbi in the Ruwenzori group thirty miles
north of the equator, are the chief African examples. A few mountains
from the East Indies, such as Kinibalu in Borneo, latitude 6° north,
have been found glaciated, though now without a snow cover. In higher
latitudes evidences of an earlier extensive glaciation have been
gathered chiefly from South America, whose extension 13° north and 56°
south of the equator, combined with the great height of its dominating
Cordillera, give it unrivaled distinction in the study of mountain
glaciation in the tropics.

Furthermore, mountain summits in tropical lands are delicate climatic
registers. In this respect they compare favorably with the inclosed
basins of arid regions, where changes in climate are clearly recorded in
shoreline phenomena of a familiar kind. Lofty mountains in the tropics
are in a sense inverted basins, the lower snowline of the past is like
the higher shoreline of an interior basin; the terminal moraines and the
alluvial fans in front of them are like the alluvial fans above the
highest strandline; the present snow cover is restricted to mountain
summits of small areal extent, just as the present water bodies are
restricted to the lowest portions of the interior basin; and successive
retreatal stages are marked by terminal moraines in the one case as they
are marked in the other by flights of terraces and beach ridges.

I made only a rapid reconnaissance across the Cordillera Vilcapampa in
the winter season, and cannot pretend from my limited observations to
solve many of the problems of the field. The data are incorporated
chiefly in the chapter on Glacial Features. In this place it is proposed
to describe only the more prominent glacial features, leaving to later
expeditions the detailed descriptions upon which the solution of some of
the larger problems must depend.

At Choquetira three prominent stages in the retreat of the ice are
recorded. The lowermost stage is represented by the great fill of
morainic and outwash material at the junction of the Choquetira, and an
unnamed valley farther south at an elevation of 11,500 feet (3,500 m.).
A mile below Choquetira a second moraine appears, elevation 12,000 feet
(3,658 m.), and immediately above the village a third at 12,800 (3,900
m.). The lowermost moraine is well dissected, the second is ravined and
broken but topographically distinct, the third is sharp-crested and
regular. A fourth though minor stage is represented by the moraine at
the snout of the living glacier and still less important phases are
represented in some valleys--possibly the record of post-glacial changes
of climate. Each main moraine is marked by an important amount of
outwash, the first and third moraines being associated with the greatest
masses. The material in the moraines represents only a part of that
removed to form the successive steps in the valley profile. The
lowermost one has an enormous volume, since it is the oldest and was
built at a time when the valley was full of waste. It is fronted by a
deep fill, over the dissected edge of which one may descend 800 feet in
half an hour. It is chiefly alluvial in character, whereas the next
higher one is composed chiefly of bowlders and is fronted by a
pronounced bowlder train, which includes a remarkable perched bowlder of
huge size. Once the valley became cleaned out the ice would derive its
material chiefly by the slower process of plucking and abrasion, hence
would build much smaller moraines during later recessional stages, even
though the stages were of equivalent length.

[Illustration: FIG. 136--Glacial sculpture on the southwestern flank of
the Cordillera Vilcapampa. Flat-floored valleys and looped terminal
moraines below and glacial steps and hanging valleys are characteristic.
The present snowfields and glaciers are shown by dotted contours.]

There is a marked difference in the degree of dissection of the
moraines. The lowermost and oldest is so thoroughly dissected as to
exhibit but little of its original surface. The second has been greatly
modified, but still possesses a ridge-like quality and marks the
beginning of a noteworthy flattening of the valley gradient. The third
is as sharp-crested as a roof, and yet was built so long ago that the
flat valley floor behind it has been modified by the meandering stream.
From this point the glacier retreated up-valley several miles
(estimated) without leaving more than the thinnest veneer on the valley
floor. The retreat must, therefore, have been rapid and without even
temporary halts until the glacier reached a position near that occupied
today. Both the present ice tongues and snowfields and those of a past
age are emphasized by the presence of a patch of scrub and woodland that
extends on the north side of the valley from near the snowline down over
the glacial forms to the lower valley levels.

The retreatal stages sketched above would call for no special comment if
they were encountered in mountains in northern latitudes. They would be
recognized at once as evidence of successive periodic retreats of the
ice, due to successive changes in temperature. To understand their
importance when encountered in very low latitudes it is necessary to
turn aside for a moment and consider two rival hypotheses of glacial
retreat. First we have the hypothesis of periodic retreat, so generally
applied to terminal moraines and associated outwash in glaciated
mountain valleys. This implies also an advance of the ice from a higher
position, the whole taking place as a result of a climatic change from
warmer to colder and back again to warmer.

[Illustration: FIG. 137--Looking up a spurless flat-floored glacial
trough near the Chucuito pass in the Cordillera Vilcapampa from 14,200
feet (4,330 m.). Note the looped terminal and lateral moraines on the
steep valley wall on the left. A stone fence from wall to wall serves to
inclose the flock of the mountain shepherd.]

[Illustration: FIG. 138--Terminal moraine in the glaciated Choquetira
Valley below Choquetira. The people who live here have an abundance of
stones for building corrals and stone houses. The upper edge of the
timber belt (cold timber line) is visible beyond the houses. Elevation
12,100 feet (3,690 m.).]

But evidences of more extensive mountain glaciation in the past do not
in themselves prove a change in climate over the whole earth. In an
epoch of fixed climate a glacier system may so deeply and thoroughly
erode a mountain mass, that the former glaciers may either diminish in
size or disappear altogether. As the work of excavation proceeds, the
catchment basins are sunk to, and at last below, the snowline; broad
tributary spurs whose snows nourish the glaciers, may be reduced to
narrow or skeleton ridges with little snow to contribute to the valleys
on either hand; the glaciers retreat and at last disappear. There
would be evidences of glaciation all about the ruins of the former
loftier mountain, but there would be no living glaciers. And yet the
climate might remain the same throughout.

It is this “topographic” hypothesis that Reiss and Stübel accept for the
Ecuadorean volcanoes. Moreover, the volcanoes of Ecuador are practically
on the equator--a very critical situation when we wish to use the facts
they exhibit in the solution of such large problems as the
contemporaneous glaciation of the two hemispheres, or the periodic
advance and retreat of the ice over the whole earth. This is not the
place to scrutinize either their facts or their hypothesis, but I am
under obligations to state very emphatically that the glacial features
of the Cordillera Vilcapampa require the climatic and not the
topographic hypothesis. Let us see why.

The differences in degree of dissection and the flattening gradient
up-valley that we noted in a preceding paragraph leave no doubt that
each moraine of the bordering valleys in the Vilcapampa region,
represents a prolonged period of stability in the conditions of
topography as well as of temperature and precipitation. If change in
topographic conditions is invoked to explain retreat from one position
to the other there is left no explanation of the periodicity of retreat
which has just been established. If a period of cold is inaugurated and
glaciers advance to an ultimate position, they can retreat only through
change of climate effected either by general causes or by topographic
development to the point where the snowfields become restricted in size.
In the case of climatic change the ice changes are periodic. In the case
of retreat due to topographic change there should be a steady or
non-periodic falling back of the ice front as the catchment basins
decrease in elevation and the snow-gathering ridges tributary to them
are reduced in height.

Further, the matterhorns of the Cordillera Vilcapampa are not bare but
snow-covered, vigorous glaciers several miles in length and large
snowfields still survive and the divides are not arêtes but broad
ridges. In addition, the last two moraines, composed of very loose
material, are well preserved. They indicate clearly that the time since
their formation has witnessed no wholesale topographic change. If (1) no
important topographic changes have taken place, and (2) a vigorous
glacier lay for a long period back of a given moraine, and (3) _suddenly
retreated several miles and again became stable_, we are left without
confidence in the application of the topographic hypothesis to the
glacial features of the Vilcapampa region. Glacial retreat may be
suddenly begun in the case of a late stage of topographic development,
but it should be an orderly retreat marked by a large number of small
moraines, or at least a plentiful strewing of the valley floor with
débris.

[Illustration: FIG. 139--Glacial features on the eastern slopes of the
Cordillera Vilcapampa.]

The number of moraines in the various glaciated valleys of the
Cordillera Vilcapampa differ, owing to differences in elevation and to
the variable size of the catchment basins. All valleys, however, display
the same sudden change from moraine to moraine and the same
characteristics of gradient. In all of them the lowermost moraine is
always more deeply eroded than the higher moraines, in all of them
glacial erosion was sufficiently prolonged greatly to modify the valley
walls, scour out lake basins, or broad flat valley floors, develop
cirques, arêtes, and pinnacled ridges in limited number. In some,
glaciation was carried to the point where only skeleton divides
remained, in most places broad massive ridges or mountain knots persist.
In spite of all these differences successive moraines were formed,
separated by long stretches either thinly covered with till or exposing
bare rock.

In examining this group of features it is important to recognize the
essential fact that though the number of moraines varies from valley to
valley, the differences in character between the moraines at low and at
high elevations in a single valley are constant. It is also clear that
everywhere the ice retreated and advanced periodically, no matter with
what topographic features it was associated, whether those of maturity
or of youth in the glacial cycle. We, therefore, conclude that
topographic changes had no significant part to play in the glacial
variations in the Cordillera Vilcapampa.

The country west of the Cordillera Vilcapampa had been reduced to early
topographic maturity before the Ice Age, and then uplifted with only
moderate erosion of the masses of the interfluves. That on the east had
passed through the same sequence of events, but erosion had been carried
much farther. The reason for this is found in a strong climatic
contrast. The eastern is the windward aspect and receives much more rain
than the western. Therefore, it has more streams and more rapid
dissection. The result was that the eastern slopes were cut to pieces
rapidly after the last great regional uplift; the broad interfluves were
narrowed to ridges. The region eastward from the crest of the Cordillera
to the Pongo de Mainique looks very much like the western half of the
Cascade Mountains in Oregon--the summit tracts of moderate declivity are
almost all consumed.

The effect of these climatic and topographic contrasts is manifested in
strong contrasts in the position and character of the glacial forms on
the opposite slopes of the range. At Pampaconas on the east the
lowermost terminal moraine is at least a thousand feet below timber
line. Between Vilcabamba pueblo and Puquiura the terminal moraine lies
at 11,200 feet (3,414 m.). By contrast the largest Pleistocene glacier
on the western slope, nearly twelve miles long, and the largest along
the traverse, ended several miles below Choquetira at 11,500 feet (3,504
m.) elevation, or just at the timber line. Thus, the steeper descents of
the eastern side of the range appear to have carried short glaciers to
levels far lower than those attained by the glaciers of the western
slope.

It seems at first strange that the largest glaciers were west of the
divide between the Urubamba and the Apurimac, that is, on the relatively
dry side of the range. The reason lies in a striking combination of
topographic and climatic conditions. Snow is a mobile form of
precipitation that is shifted about by the wind like a sand dune in the
desert. It is not required, like water, to begin a downhill movement as
soon as it strikes the earth. Thus, it is a noteworthy fact that snow
drifting across the divides may ultimately cause the largest snowfields
to lie where the least snow actually falls. This is illustrated in the
Bighorns of Wyoming and others of our western ranges. It is, however,
not the wet snow near the snowline, but chiefly the dry snow of higher
altitudes that is affected. What is now the dry or leeward side of the
Cordillera appears in glacial times to have actually received more snow
than the wet windward side.

[Illustration: FIG. 140--Glacial sculpture in the heart of the
Cordillera Vilcapampa. In places the topography has so high a relief
that the glaciers seem almost to overhang the valleys. See Figs. 96 and
179 for photographs.]

The topography conspired to increase this contrast. In place of many
streams, direct descents, a dispersion of snow in many valleys, as on
the east, the western slopes had indirect descents, gentler valley
profiles, and that higher degree of concentration of drainage which
naturally goes with topographic maturity. For example, there is nothing
in the east to compare with the big spurless valley near the pass above
Arma. The side walls were so extensively trimmed that the valley was
turned into a trough. The floor was smoothed and deepened and all the
tributary glaciers were either left high up on the bordering slopes or
entered the main valley with very steep profiles; their lateral and
terminal moraines now hang in festoons on the steep side walls.
Moreover, the range crest is trimmed from the west so that the serrate
skyline is a feature rarely seen from eastern viewpoints. This may not
hold true for more than a small part of the Cordillera. It was probably
emphasized here less by the contrasts already noted than by the geologic
structure. The eastward-flowing glaciers descended over dip slopes on
highly inclined sandstones, as at Pampaconas. Those flowing westward
worked either in a jointed granite or on the outcropping _edges_ of the
sandstones, where the quarrying process known as glacial plucking
permitted the development of excessively steep slopes.

There are few glacial steps in the eastern valleys. The western valleys
have a marvelous display of this striking glacial feature. The
accompanying hachure maps show them so well that little description is
needed. They are from 50 to 200 feet high. Each one has a lake at its
foot into which the divided stream trickles over charming waterfalls.
All of them are clearly associated with a change in the volume of the
glacier that carved the valley. Wherever a tributary glacier entered, or
the side slopes increased notably in area, a step was formed. By retreat
some of them became divided, for the process once begun would push the
step far up valley after the manner of an extinguishing waterfall.

The retreat of the steps, the abrasion of the rock, and the sapping of
the cirques at the valley heads excavated the upper valleys so deeply
that they are nearly all, as W. D. Johnson has put it, “down at the
heel.” Thus, above Arma, one plunges suddenly from the smooth, grassy
glades of the strongly glaciated valley head down over the outer slopes
of the lowermost terminal moraine to the steep lower valley. Above the
moraine are fine pastures, in the steep valley below are thickets and
rocky defiles. There are long quiet reaches in the streams of the
glaciated valley heads besides pretty lakes and marshes. Below, the
stream is swift, almost torrential. Arma itself is built upon alluvial
deposits of glacial origin. A mile farther down the valley is
constricted and steep-walled--really a canyon.

Though the glaciers have retreated to the summit region, they are by no
means nearing extinction. The clear blue ice of the glacier descending
from Mt. Soiroccocha in the Arma Valley seems almost to hang over the
precipitous valley border. In curious contrast to its suggestion of cold
and storm is the patch of dark green woodland which extends right up to
its border. An earthquake might easily cause the glacier to invade the
woodland. Some of the glaciers between Choquetira and Arma rest on
terminal moraines whose distal faces are from 200 to 300 feet high. The
ice descending southeasterly from Panta Mt. is a good illustration.
Earlier positions of the ice front are marked by equally large moraines.
The one nearest that engaged by the living glacier confines a large lake
that discharges through a gap in the moraine and over a waterfall to the
marshy floor of the valley.

Retreat has gone so far, however, that there are only a few large
glacier systems. Most of the tributaries have withdrawn toward their
snowfields. In place of the twenty distinct glaciers now lying between
the pass and the terminal moraine below Choquetira, there was in glacial
times one great glacier with twenty minor tributaries. The cirques now
partly filled with damp snow must then have been overflowing with dry
snow above and ice below. Some of the glaciers were over a thousand feet
thick; a few were nearly two thousand feet thick, and the cirques that
fed them held snow and ice at least a half mile deep. Such a remarkably
complete set of glacial features only 700 miles from the equator is
striking evidence of the moist climate on the windward eastern part of
the great Andean Cordillera, of the universal change in climate in the
glacial period, and of the powerful dominating effects of ice erosion in
this region of unsurpassed Alpine relief.

THE VILCAPAMPA BATHOLITH AND ITS TOPOGRAPHIC EFFECTS

[Illustration: FIG. 141--Composite geologic section on the northeastern
border of the Cordillera Vilcapampa, in the vicinity of Pampaconas, to
show the deformative effects of the granite intrusion. There is a
limited amount of limestone near the border of the Cordillera. Both
limestone and sandstone are Carboniferous. See Appendix B. See also
Figs. 142 and 146. The section is about 15 miles long.]

The main axis of the Cordillera Vilcapampa consists of granite in the
form of a batholith between crystalline schists on the one hand
(southwest), and Carboniferous limestones and sandstones and Silurian
shales and slates on the other (northeast). It is not a domal uplift in
the region in which it was observed in 1911, but an axial intrusion, in
places restricted to a narrow belt not more than a score of miles
across. As we should expect from the variable nature of the invaded
material, the granite belt is not uniform in width nor in the character
of its marginal features. In places the intrusion has produced
strikingly little alteration of the country rock; in other localities
the granite has been injected into the original material in so intimate
a manner as almost completely to alter it, and to give rise to a very
broad zone of highly metamorphosed rock. Furthermore, branches were
developed so that here and there tributary belts of granite extend from
the main mass to a distance of many miles. Outlying batholiths occur
whose common petrographic character and similar manner of occurrence
leave little doubt that they are related abyssally to a common plutonic
mass.

The Vilcapampa batholith has two highly contrasted borders, whether we
consider the degree of metamorphism of the country rock, the definition
of the border, or the resulting topographic forms. On the northeastern
ridge at Colpani the contact is so sharp that the outstretched arms in
some places embrace typical granite on the one hand and almost
unaltered shales and slates on the other. Inclusions or xenoliths of
shale are common, however, ten and fifteen miles distant, though they
are prominent features in a belt only a few miles wide. The lack of more
intense contact effects is a little remarkable in view of the altered
character of the inclusions, all of which are crystalline in contrast to
the fissile shales from which they are chiefly derived. Inclusions
within a few inches of the border fall into a separate class, since they
show in general but trifling alteration and preserve their original
cleavage plains. It appears that the depth of the intrusion must have
been relatively slight or the intrusion sudden, or both shallow and
sudden, conditions which produce a narrow zone of metamorphosed material
and a sharp contact.

[Illustration: FIG. 142--The deformative effects of the Vilcapampa
intrusion on the northeastern border of the Cordillera. The deformed
strata are heavy-bedded sandstones and shales and the igneous rocks are
chiefly granites with bordering porphyries. Looking northwest near
Puquiura. For conditions near Pampaconas, looking in the opposite
direction, see Fig. 141. For conditions on the other side of the
Cordillera, see Fig. 146.]

The relation between shale and granite at Colpani is shown in Fig. 143.
Projections of granite extend several feet into the shale and slate and
generally end in blunt barbs or knobs. In a few places there is an
intimate mixture of irregular slivers and blocks of crystallized
sediments in a granitic groundmass, with sharp lines of demarcation
between igneous and included material. The contact is vertical for at
least several miles. It is probable that other localities on the contact
exhibit much greater modification and invasion of the weak shales and
slates, but at Colpani the phenomena are both simple and restricted in
development.

[Illustration: FIG. 143--Relation of granite intrusion to schist on the
northeastern border of the Vilcapampa batholith near the bridge of
Colpani, lower end of the granite Canyon of Torontoy. The sections are
from 15 to 25 feet high and represent conditions at different levels
along the well-defined contact.]

The highly mineralized character of the bordering sedimentary strata,
and the presence of numbers of complementary dikes, nearly identical in
character to those in the parent granite now exposed by erosion over a
broad belt roughly parallel to the contact, supplies a basis for the
inference that the granite may underlie the former at a slight depth, or
may have had far greater metamorphic effects upon its sedimentary roof
than the intruded granite has had upon its sedimentary rim.

The physiographic features of the contact belt are of special interest.
No available physiographic interpretation of the topography of a
batholith includes a discussion of those topographic and drainage
features that are related to the lithologic character of the intruded
rock, the manner of its intrusion, or the depth of erosion since
intrusion. Yet each one of these factors has a distinct topographic
effect. We shall, therefore, turn aside for a moment from the detailed
discussion of the Vilcapampa region to an examination of several
physiographic principles and then return to the main theme for
applications.

It is recognized that igneous intrusions are of many varieties and that
even batholithic invasions may take place in rather widely different
ways. Highly heated magmas deeply buried beneath the earth’s surface
produce maximum contact effects, those nearer the surface may force the
strata apart without extreme lithologic alterations of the displaced
beds, while through the stoping process a sedimentary cover may be
largely absorbed and the magmas may even break forth at the surface as
in ordinary vulcanism. If the sedimentary beds have great vertical
variation in resistance, in attitude, and in composition, there may be
afforded an opportunity for the display of quite different effects at
different levels along a given contact, so that a great variety of
physical conditions will be passed by the descending levels of erosion.
At one place erosion may have exposed only the summit of the batholith,
at another the associated dikes and sheets and ramifying branches may be
exposed as in the zone of fracture, at a third point the original zone
of flowage may be reached with characteristic marginal schistosity,
while at still greater depths there may be uncovered a highly
metamorphosed rim of resistant sedimentary rock.

The mere enumeration of these variable structural features is sufficient
to show how variable we should expect the associated land forms to be.
Were the forms of small extent, or had they but slight distinction upon
comparison with other erosional effects, they would be of little
concern. They are, on the contrary, very extensively developed; they
affect large numbers of lofty mountain ranges besides still larger areas
of old land masses subjected to extensive and deep erosion, thus laying
bare many batholiths long concealed by a thick sedimentary roof.

The differences between intruded and country rock dependent upon these
diversified conditions of occurrence are increased or diminished
according to the history of the region after batholithic invasion takes
place. Regional metamorphism may subsequently induce new structures or
minimize the effects of the old. Joint systems may be developed, the
planes widely spaced in one group of rocks giving rise to monolithic
masses very resistant to the agents of weathering, while those of an
adjacent group may be so closely spaced as greatly to hasten the rate of
denudation. There may be developed so great a degree of schistosity in
one rock as to give rise (with vigorous erosion) to a serrate
topography; on the other hand the forms developed on the rocks of a
batholith may be massive and coarse-textured.

To these diversifying conditions may be added many others involving a
large part of the field of dynamic geology. It will perhaps suffice to
mention two others: the stage of erosion and the special features
related to climate. If a given intrusion has been accompanied by an
important amount of uplift or marginal compression, vigorous erosion may
follow, whereupon a chance will be offered for the development of the
greatest contrast in the degree of boldness of topographic forms
developed upon rocks of unequal resistance. Ultimately these contrasts
will diminish in intensity, as in the case of all regional differences
of relief, with progress toward the end of the normal cycle of erosion.
If peneplanation ensue, only feeble topographic differences may mark
the line of contact which was once a prominent topographic feature. With
reference to the effects of climate it may be said simply that a granite
core of batholithic origin may extend above the snowline or above timber
line or into the timbered belt, whereas the invaded rock may occur
largely below these levels with obvious differences in both the rate and
the kind of erosion affecting the intruded mass.

[Illustration: FIG. 144--Cliffed canyon wall in the Urubamba Valley
between Huadquiña and Torontoy. There is a descent of nearly 2,000 feet
shown in the photograph and it is developed almost wholly along
successive joint planes.]

[Illustration: FIG. 145--Another aspect of the canyon wall of Fig. 144.
The almost sheer descents are in contrast with the cliff and platform
type of topography characteristic of the Grand Canyon of Colorado.]

If we apply the foregoing considerations to the Cordillera Vilcapampa,
we shall find some striking illustrations of the principles involved.
The invasion of the granite was accompanied by moderate absorption of
the displaced rock, and more especially by the marginal pushing aside of
the sedimentary rim. The immediate effect must have been to give both
intruded rock and country rock greater height and marked ruggedness.
There followed a period of regional compression and torsion, and the
development of widespread joint systems with strikingly regular
features. In the Silurian shales and slates these joints are closely
spaced; in the granites they are in many places twenty to thirty feet
apart. The shales, therefore, offer many more points of attack and have
weathered down into a smooth-contoured topography boldly overlooked
along the contact by walls and peaks of granite. _In some cases a canyon
wall a mile high is developed entirely on two or three joint planes
inclined at an angle no greater than 15°._ The effect in the granite is
to give a marked boldness of relief, nowhere more strikingly exhibited
than at Huadquiña, below Colpani, where the foot-hill slopes developed
on shales and slates suddenly become moderate. The river flows from a
steep and all but uninhabited canyon into a broad valley whose slopes
are dotted with the terraced _chacras_, or farms, of the mountain
Indians.

The Torontoy granite is also homogeneous while the shales and slates
together with their more arenaceous associates occur in alternating
belts, a diversity which increases the points of attack and the
complexity of the forms. Tending toward the same result is the greater
hardness of the granite. The tendency of the granite to develop bold
forms is accelerated in lofty valleys disposed about snow-clad peaks,
where glaciers of great size once existed, and where small glaciers
still linger. The plucking action of ice has an excellent chance for
expression, since the granite may be quarried cleanly without the
production of a large amount of spoil which would load the ice and
diminish the intensity of its plucking action.

As a whole the Central Andes passed through a cycle of erosion in late
Tertiary time which was interrupted by uplift after the general surface
had been reduced to a condition of topographic maturity. Upon the
granites mature slopes are not developed except under special conditions
(1) of elevation as in the small batholith above Chuquibambilla, and (2)
where the granite is itself bordered by resistant schists which have
upheld the surface over a broad transitional belt. Elsewhere the granite
is marked by exceedingly rugged forms: deep steep-walled canyons,
precipitous cirques, matterhorns, and bold and extended escarpments of
erosion. In the shale belt the trails run from valley to valley in every
direction without special difficulties, but in the granite they follow
the rivers closely or cross the axis of the range by carefully selected
routes which generally reach the limit of perpetual snow. Added interest
attaches to these bold topographic forms because of the ruins now found
along the canyon walls, as at Torontoy, or high up on the summit of a
precipitous spur, as at Machu Picchu near the bridge of San Miguel.

The Vilcapampa batholith is bordered on the southwest by a series of
ancient schists with which the granite sustains quite different
relations. No sharp dividing line is visible, the granite extending
along the planes of foliation for such long distances as in places to
appear almost interbedded with the schists. The relation is all the more
striking in view of the trifling intrusions effected in the case of the
seemingly much weaker shales on the opposite contact. Nor is the
metamorphism of the invaded rock limited to simple intrusion. For
several miles beyond the zone of intenser effects the schists have been
enriched with quartz to such an extent that their original darker color
has been changed to light gray or dull white. At a distance they may
even appear as homogeneous and light-colored as the granite. At distant
points the schists assume a darker hue and take on the characters of a
rather typical mica schist.

It is probable that the Vilcapampa intrusion is one of a family of
batholiths which further study may show to extend over a much larger
territory. The trail west of Abancay was followed quite closely and
accidentally crosses two small batholiths of peculiar interest. Their
limits were not closely followed out, but were accurately determined at
a number of points and the remaining portion of the contact inferred
from the topography. In the case of the larger area there may indeed be
a connection westward with a larger mass which probably constitutes the
ranges distant some five to ten miles from the line of traverse.

[Illustration: FIG. 146--Deformative effects on limestone strata of the
granite intrusion on the southwestern border of the Vilcapampa batholith
above Chuquibambilla. Fig. 147 is on the same border of the batholith
several miles farther northwest. The granite mass on the right is a
small outlier of the main batholith looking south. The limestone is
Cretaceous. See Appendix C for locations.]

These smaller intrusions are remarkable in that they appear to have been
attended by little alteration of either invading or invaded rock, though
the granites were observed to become distinctly more acid in the contact
zone. Space was made for them by displacing the sedimentary cover and by
a marked shortening of the sedimentary rim through such structures as
overthrust faults and folds. The contact is observable in a highly
metamorphosed belt about twenty feet wide, and for several hundred feet
more the granite has absorbed the limestone in small amounts with the
production of new minerals and the development of a distinctly lighter
color. The deformative effects of the batholithic invasion are shown in
their gross details in Figs. 141, 142, and 146; the finer details of
structure are represented in Fig. 147, which is drawn from a measured
outcrop above Chuquibambilla.

It will be seen that we have here more than a mere crinkling, such as
the mica schists of the Cordillera Vilcapampa display. The diversified
sedimentary series is folded and faulted on a large scale with broad
structural undulations visible for miles along the abrupt valley walls.
Here and there, however, the strata become weaker generally through the
thinning of the beds and the more rapid alternation of hard and soft
layers, and for short distances they have absorbed notable amounts of
the stresses induced by the igneous intrusions. In such places not only
the structure but the composition of the rock shows the effects of the
intrusion. Certain shales in the section are carbonaceous and in all
observed cases the organic matter has been transformed to anthracite, a
condition generally associated with a certain amount of minute mashing
and a cementation of both limestone and sandstone.

[Illustration: FIG. 147--Overthrust folds in detail on the southwestern
border of the Vilcapampa batholith near Chuquibambilla. The section is
fifteen feet high. Elevation, 13,100 feet (4,000 m.). For comparison
with the structural effects of the Vilcapampa intrusion on the northeast
see Fig. 142.]

The granite becomes notably darker on approach to the northeastern
contact near Colpani; the proportion of ferro-magnesian minerals in some
cases is so large as to give a distinctly black color in sharp contrast
to the nearly white granite typical of the central portion of the mass.
Large masses of shale foundered in the invading magma, and upon fusion
gave rise to huge black masses impregnated with quartz and in places
smeared or injected with granite magma. Everywhere the granite is marked
by numbers of black masses which appear at first sight to be
aggregations of dark minerals normal to the granite and due to
differentiation processes at the time of crystallization. It is,
however, noteworthy that these increase rapidly in number on approach to
the contact, until in the last half-mile they appear to grade into the
shale inclusions. It may, therefore, be doubted that they are
aggregations. From their universal distribution, their uniform
character, and their marked increase in numbers on approach to lateral
contacts, it may reasonably be inferred that they represent foundered
masses of country rock. Those distant from present contacts are in
almost all cases from a few inches to a foot in diameter, while on
approach to lateral contacts they are in places ten to twenty feet in
width, as if the smaller areas represented the last remnants of large
inclusions engulfed in the magma near the upper or roof contact. They
are so thoroughly injected with silica and also with typical granite
magma as to make their reference to the country rock less secure on
petrographical than on purely distributional grounds.

A parallel line of evidence relates to the distribution of complementary
dikes throughout the granite. In the main mass of the batholith the
dikes are rather evenly distributed as to kind with a slight
preponderance of the dark-colored group. Near the contact, however,
aplitic dikes cease altogether and great numbers of melanocratic dikes
appear. It may be inferred that we have in this pronounced condition
suggestions of strong influence upon the final processes of invasion and
cooling of the granite magma, on the part of the country rock detached
and absorbed by the invading mass. It might be supposed that the
indicated change in the character of the complementary dikes could be
ascribed to possible differentiation of the granite magma whereby a
darker facies would be developed toward the Colpani contact. It has,
however, been pointed out already that the darkening of the granite in
this direction is intimately related to a marked increase in the number
of inclusions, leaving little doubt that the thorough digestion of the
smaller masses of detached shales is responsible for the marked increase
in the number and variety of the ferro-magnesian and special contact
minerals.

Upon the southwestern border of the batholith the number of aplitic
dikes greatly increases. They form prominent features, not only of the
granite, but also of the schists, adding greatly to the strong contrast
between the schist of the border zone and that outside the zone of
metamorphism. In places in the border schists, these are so numerous
that one may count up to twenty in a single view, and they range in size
from a few inches to ten or fifteen feet. The greater fissility of the
schists as contrasted with the shales on the opposite or eastern margin
of the batholith caused them to be relatively much more passive in
relation to the granite magma. They were not so much torn off and
incorporated in the magma, as they were thoroughly injected and
metamorphosed. Added to this is the fact that they are petrographically
more closely allied to the granite than are the shales upon the
northeastern contact.

CHAPTER XIV

THE COASTAL TERRACES

Along the entire coast of Peru are upraised and dissected terraces of
marine origin. They extend from sea level to 1,500 feet above it, and
are best displayed north of Mollendo and in the desert south of Payta.
The following discussion relates to that portion of the coast between
Mollendo and Camaná.

At the time of the development of the coastal terraces the land was in a
state of temporary equilibrium, for the terraces were cut to a mature
stage as indicated by the following facts: (1) the terraces have great
width--from one to five and more miles; (2) their inner border is
straight, or, where curves exist, they are broad and regular; (3) the
terrace tops are planed off smoothly so that they now have an even
gradient and an almost total absence of rock stacks or unreduced spurs;
(4) the mature slopes of the Coast Range, strikingly uniform in gradient
and stage of development (Fig. 148), are perfectly organized with
respect to the inner edge of the terrace. They descend gradually to the
terrace margin, showing that they were graded with respect to sea level
when the sea stood at the inner edge of the highest terrace.

From the composition and even distribution of the thick-bedded Tertiary
deposits of the desert east of the Coast Range, it is concluded that the
precipitation of Tertiary time was greater than that of today (see p.
261). Therefore, if the present major streams reach the sea, it may also
be concluded that those of an earlier period reached the sea, provided
the topography indicates the perfect adjustment of streams to structure.
Lacustrine sediments are absent throughout the Tertiary section. Such
through-flowing streams, discharging on a stable coast, would also have
mature valleys as a consequence of long uninterrupted erosion at a fixed
level. The Majes river must have cut through the Coast Range at Camaná
then as now. Likewise the Vitor at Quilca must have cut straight across
the Coast Range. An examination of the surface leading down from the
Coast Range to the upper edge of these valleys fully confirms this
deduction. Flowing and well-graded slopes descend to the brink of the
inner valley in each case, where they give way to the gorge walls that
continue the descent to the valley floor.

Confirmatory evidence is found in the wide Majes Valley at Cantas and
Aplao. (See the Aplao Quadrangle for details.) Though the observer is
first impressed with the depth of the valley, its width is more
impressive still. It is also clear that two periods of erosion are
represented on its walls. Above Aplao the valley walls swing off to the
west in a great embayment quite inexplicable on structural grounds; in
fact the floor of the embayment is developed across the structure, which
is here more disordered than usual. The same is true below Cantas, as
seen from the trail, which drops over two scarps to get to the valley
floor. The upper, widely opened valley is correlated with the latter
part of the period in which were formed the mature terraces of the coast
and the mature slopes bordering the larger valleys where they cross the
Coast Range.

After its mature development the well-graded marine terrace was upraised
and dissected. The deepest and broadest incisions in it were made where
the largest streams crossed it. Shallower and narrower valleys were
formed where the smaller streams that headed in the Coast Range flowed
across it. Their depth and breadth was in general proportional to the
height of that part of the Coast Range in which their headwaters lay and
to the size of their catchment basins.

When the dissection of the terrace had progressed to the point where
about one-third of it had been destroyed, there came depression and the
deposition of Pliocene or early Pleistocene sands, gravels, and local
clay beds. Everywhere the valleys were partly or wholly filled and over
broad stretches, as in the vicinity of stream mouths and upon lower
portions of the terrace, extensive deposits were laid down. The largest
deposits lie several hours’ ride south of Camaná, where locally they
attain a thickness of several hundred feet. Their upper surface was well
graded and they show a prolonged period of deposition in which the
former coastal terrace was all but concealed.

[Illustration: FIG. 148--The Coast Range between Mollendo and Arequipa
at the end of June, 1911. There is practically no grass and only a few
dry shrubs. The fine network over the hill slopes is composed of
interlacing cattle tracks. The cattle roam over these hills after the
rains which come at long intervals. (See page 141 for description of the
rains and the transformations they effect. For example, in October,
1911, these hills were covered with grass.)]

[Illustration: FIG. 149--The great marine terrace at Mollendo. See Fig.
150 for profile.]

The uplift of the coast terrace and its subsequent dissection bring the
physical history down to the present. The uplift was not uniform; three
notches in the terrace show more faintly upon the granite-gneiss where
the buried rock terrace has been swept clean again, more strongly upon
the softer superimposed sands. They lie below the 700-foot contour and
are insignificant in appearance beside the slopes of the Coast Range or
the ragged bluff of the present coast.

The effect of the last uplift of the coast was to impel the Majes River
again to cut down its lower course nearly to sea level. The Pliocene
terrace deposits are here entirely removed over an area several leagues
wide. In their place an extensive delta and alluvial fan have been
formed. At first the river undoubtedly cut down to base level at its
mouth and deposited the cut material on the sea floor, now shoal, for a
considerable distance from shore. We should still find the river in that
position had other agents not intervened. But in the Pleistocene a great
quantity of waste was swept into the Majes Valley, whereupon aggradation
began; and in the middle and lower valley it has continued down to the
present.

[Illustration: FIG. 150--Profile of the coastal terraces at Mollendo. At
1, in a tributary gorge, fossiliferous clay occurs at 800 feet elevation
above the sea. At 2 is a characteristic change of profile marking a drop
from a higher to a lower terrace. On the extreme left is the highest
terrace, just under 1,500 feet (460 m.).]

[Illustration: FIGS. 151-154--These four diagrams represent the physical
history and the corresponding physiographic development of the coastal
region of Peru between Camaná and Mollendo. The sedimentary beds in the
background of the first diagram are hypothetical and are supposed to
correspond to the quartzites of the Majes Valley at Aplao.]

The effect has been not only the general aggradation of the valley
floor, but also the development of a combined delta and superimposed
alluvial fan at the valley mouth. The seaward extension of the delta has
been hastened by the gradation of the shore between the bounding
headlands, thus giving rise to marine marshes in which every particle of
contributed waste is firmly held. The plain of Camaná, therefore,
includes parts of each of the following: a delta, a superposed alluvial
fan, a salt-water marsh, a fresh-water marsh, a series of beaches, small
amounts of piedmont fringe at the foot of Pliocene deposits once trimmed
by the river and by waves, and extensive tracts of indefinite fill. (See
the Camaná Quadrangle for details.)

With the coastal conditions now before us it will be possible to attempt
a correlation between the erosion features and the deposits of the coast
and those of the interior. An understanding of the comparisons will be
facilitated by the use of diagrams, Figs. 151-154, and by a series of
concise summary statements. From the relations of the figure it appears
that:

1. The Tertiary deposits bordering the Majes Valley east of the Coast
Range were in process of deposition when the sea planed the coastal
terrace (Fig. 151).

2. A broad mature marine terrace without stacks or sharply alternating
spurs and reëntrants (though the rock is a very resistant granite) is
correlated with the mature grades of the Coast Range, with which they
are integrated and with the mature profiles of the main Cordillera.

3. Such a high degree of topographic organization requires the
dissection in the _late_ stages of the erosion cycle of at least the
inner or eastern border of the piedmont deposits of the desert, largely
accumulated during the _early_ stages of the cycle.

4. Since the graded slopes of the Coast Range on the one side descend to
a former shore whose elevation is now but 1,500 feet above sea level,
and since only ten to twenty miles inland on the other side of the
range, the same kind of slope extends beneath Tertiary deposits 4,000
feet above sea level, it appears that aggradation of the outer (or
western) part of the Tertiary deposits on the eastern border of the
Coast Range continued down to the end of the cycle of erosion, though

5. There must have been an outlet to the sea, since, as we have already
seen, the water supply of the Tertiary was greater than that of today
and the present streams reach the sea. Moreover, the mature upper slopes
and the steep lower slopes of the large valleys make a pronounced
topographic unconformity, showing two cycles of valley development.

6. Upon uplift of the coast and dissection of the marine terraces at the
foot of the Coast Range, the streams cut deep trenches on the floors of
their former valleys (Fig. 152) and removed (a) large portions of the
coast terrace, and (b) large portions of the Tertiary deposits east of
the Coast Range.

7. Depression of the coastal terrace and its partial burial meant the
drowning of the lower Majes Valley and its partial filling with marine
and later with terrestrial deposits. It also brought about the partial
filling by stream aggradation of the middle portion of the valley,
causing the valley fill to abut sharply against the steep valley walls.
(See Fig. 155.)

8. Uplift and dissection of both the terrace and its overlying sediments
would be accompanied by dissection of the former valley fill, provided
that the waste supply was not increased and that the uplift was regional
and approximately equal throughout--not a bowing up of the coast on the
one hand, or an excessive bowing up of the mountains on the other. But
the waste supply has not remained constant, and the uplift has been
greater in the Cordillera than on the coast. Let us proceed to the proof
of these two conclusions, since upon them depends the interpretation of
the later physical history of the coastal valleys.

[Illustration: FIG. 155--Steep walls in the Majes Valley below Cantas
and the abrupt termination against them of a deep alluvial fill.]

[Illustration: FIG. 156--Canyon of the Majes River through the Coast
Range north of Camaná. The rock is a granite-gneiss capped by rather
flat-lying sedimentaries.]

It is known that the Pleistocene was a time of augmented waste delivery.
At the head of the broadly opened Majes Valley there was deposited a
huge mass of extremely coarse waste several hundred feet deep and
several miles long. Forward from it, interstratified with its outer
margin, and continuing the same alluvial grade, is a still greater mass
of finer material which descends to lower levels. The fine material is
deposited on the floor of a valley cut into Tertiary strata, hence it
is younger than the Tertiary. It is now, and has been for some time
past, in process of dissection, hence it was not formed under present
conditions of climate and relief. It is confidently assigned to the
Pleistocene, since this is definitely known to have been a time of
greater precipitation and waste removal on the mountains, and deposition
on the plains and the floors of mountain valleys. Such a conclusion
appears, even on general grounds, to be but a shade less reliable than
if we were able to find in the upper Majes Valley, as in so many other
Andean valleys, similar alluvial deposits interlocked with glacial
moraines and valley trains.

In regard to the second consideration--the upbowing of the
Cordillera--it may be noted that the valley and slope profiles of the
main Cordillera shown on p. 191, when extended toward the margin of the
mountain belt, lie nearly a mile above the level of the sea on the west
and the Amazon plains on the east. The evidence of regional bowing thus
afforded is checked by the depths of the mountain valleys and the stream
profiles in them. The streams are now sunk from one to three thousand
feet below their former level. Even in the case of three thousand feet
of erosion the stream profiles are still ungraded, the streams
themselves are almost torrential, and from one thousand to three
thousand feet of vertical cutting must still be accomplished before the
profiles will be as gentle and regular as those of the preceding cycle
of erosion, in which were formed the mature slopes now lying high above
the valley floors.

Further evidence of bowing is afforded by the attitude of the Tertiary
strata themselves, more highly inclined in the case of the older
Tertiary, less highly inclined in the case of the younger Tertiary. It
is noteworthy that the gradient of the present valley floor is
distinctly less than that of the least highly inclined strata. This is
true even where aggradation is now just able to continue, as near the
nodal point of the valley, above Aplao, where cutting ceases and
aggradation begins. (See the Aplao Quadrangle for change of function on
the part of the stream a half mile above Cosos). Such a progressive
steepening of gradients in the direction of the oldest deposits, shows
very clearly a corresponding progression in the growth of the Andes at
intervals throughout the Tertiary.

Thus we have aggradation in the Tertiary at the foot of the growing
Andes; aggradation in the Pliocene or early Pleistocene on the floor of
a deep valley cut in earlier deposits; aggradation in the glacial epoch;
and aggradation now in progress. Basin deposits within the borders of
the Peruvian Andes are relatively rare. The profound erosion implied by
the development, first of a mature topography across this great
Cordillera, and second of many deep canyons, calls for deposition on an
equally great scale on the mountain borders. The deposits of the western
border are a mile thick, but they are confined to a narrow zone between
the Coast Range and the Cordillera. Whatever material is swept beyond
the immediate coast is deposited in deep ocean water, for the bottom
falls off rapidly. The deposits of the eastern border of the Andes are
carried far out over the Amazon lowland. Those of earlier geologic
periods were largely confined to the mountain border, where they are now
upturned to form the front range of the Andes. The Tertiary deposits of
the eastern border are less restricted, though they appear to have
gathered chiefly in a belt from fifty to one hundred miles wide.

The deposits of the western border were laid down by short streams
rising on a divide only 100 to 200 miles from the Pacific. Furthermore,
they drain the dry leeward slopes of the Andes. The deposits of the wet
eastern border were made by far larger streams that carry the waste of
nearly the whole Cordillera. Their shoaling effect upon the Amazon
depression must have been a large factor in its steady growth from an
inland sea to a river lowland.

CHAPTER XV

PHYSIOGRAPHIC AND GEOLOGIC DEVELOPMENT

GENERAL FEATURES

In the preceding chapter we employed geologic facts in the determination
of the age of the principal topographic forms. These facts require
further discussion in connection with their closest physiographic allies
if we wish to show how the topography of today originated. There are
many topographic details that have a fundamental relation to structure;
indeed, without a somewhat detailed knowledge of geology only the
broader and more general features of the landscape can be interpreted.
In this chapter we shall therefore refer not to the scenic features as
in a purely topographic description, but to the rock structure and the
fossils. A complete and technical geologic discussion is not desirable,
first, because it should be based upon much more detailed geologic field
work, and second because after all our main purpose is not to discuss
the geologic features _per se_, but the physiographic background which
the geologic facts afford. I make this preliminary observation partly to
indicate the point of view and partly to emphasize the necessity, in a
broad, geographic study, for the reconstruction of the landscapes of the
past.

The two dominating ranges of the Peruvian Andes, called the Maritime
Cordillera and the Cordillera Vilcapampa, are composed of igneous
rock--the one volcanic lava, the other intrusive granite. The chief rock
belts of the Andes of southern Peru are shown in Fig. 157. The Maritime
Cordillera is bordered on the west by Tertiary strata that rest
unconformably upon Palaeozoic quartzites. It is bordered on the east by
Cretaceous limestones that grade downward into sandstones, shales, and
basal conglomerates. At some places the Cretaceous deposits rest upon
old schists, at others upon Carboniferous limestones and related
strata, upon small granite intrusives and upon old and greatly altered
volcanic rock.

The Cordillera Vilcapampa has an axis of granitic rock which was thrust
upward through schists that now border it on the west and slates that
now border it on the east. The slate series forms a broad belt which
terminates near the eastern border of the Andes, where the mountains
break down abruptly to the river plains of the Amazon Basin. The
immediate border on the east is formed of vertical Carboniferous
limestones. The narrow foothill belt is composed of Tertiary sandstones
that grade into loose sands and conglomerates. The inclined Tertiary
strata were leveled by erosion and in part overlain by coarse and now
dissected river gravels, probably of Pleistocene age. Well east of the
main border are low ranges that have never been described. They could
not be reached by the present expedition on account of lack of time. On
the extreme western border of that portion of the Peruvian Andes herein
described, there is a second distinct border chain, the Coast Range. It
is composed of granite and once had considerable relief, but erosion has
reduced its former bold forms to gentle slopes and graded profiles.

The continued and extreme growth of the Andes in later geologic periods
has greatly favored structural and physiographic studies. Successive
uplifts have raised earlier deposits once buried on the mountain flanks
and erosion has opened canyons on whose walls and floors are the clearly
exposed records of the past. In addition there have been igneous
intrusions of great extent that have thrust aside and upturned the
invaded strata exposing still further the internal structures of the
mountains. From sections thus revealed it is possible to outline the
chief events in the history of the Peruvian Andes, though the outline is
still necessarily broad and general because based on rapid
reconnaissance. However, it shows clearly that the landscape of the
present represents but a temporary stage in the evolution of a great
mountain belt. At the dawn of geologic history there were chains of
mountains where the Andes now stand. They were swept away and even their
roots deeply submerged under invading seas. Repeated uplifts of the
earth’s crust reformed the ancient chains or created new ones out of the
rock waste derived from them. Each new set of forms, therefore, exhibits
some features transmitted from the past. Indeed, the landscape of today
is like the human race--inheriting much of its character from past
generations. For this reason the philosophical study of topographic
forms requires at least a broad knowledge of related geologic
structures.

[Illustration: FIG. 157--Outline sketch showing the principal rock belts
of Peru along the seventy-third meridian. They are: _1_, Pleistocene and
Recent gravels and sands, the former partly indurated and slightly
deformed, with the degree of deformation increasing toward the mountain
border (south). _2_, Tertiary sandstones, inclined from 15° to 30°
toward the north and unconformably overlain by Pleistocene gravels. _3_,
fossil-bearing Carboniferous limestones with vertical dip. _4_,
non-fossiliferous slates, shales, and slaty schists (Silurian) with
great variation in degree of induration and in type of structure. South
of the parallel of 13° is a belt of Carboniferous limestones and
sandstones bordering (_5_), the granite axis of the Cordillera
Vilcapampa. For its structural relations to the Cordillera see Figs. 141
and 142. _6_, old and greatly disturbed volcanic agglomerates, tuffs and
porphyries, and quartzitic schists and granite-gneiss. _7_, principally
Carboniferous limestones north of the axis of the Central Ranges and
Cretaceous limestones south of it. Local granite batholiths in the axis
of the Central Ranges. _8_, quartzites and slates predominating with
thin limestones locally. South of 8 is a belt of shale, sandstone, and
limestone with a basement quartzite appearing on the valley floors. _9_,
a portion of the great volcanic field of the Central Andes and
characteristically developed in the Western or Maritime Cordillera,
throughout northern Chile, western Bolivia, and Peru. At Cotahuasi (see
also Fig. 20) Cretaceous limestones appear beneath the lavas. _10_,
Tertiary sandstones of the coastal desert with a basement of old
volcanics and quartzites appearing on the valley walls. The valley floor
is aggraded with Pleistocene and Recent alluvium. _11_, granite-gneiss
of the Coast Range. _12_, late Tertiary or Pleistocene sands and gravels
deposited on broad coastal terraces. For rock structure and character
see the other figures in this chapter. For a brief designation of index
fossils and related forms see Appendix B. For the names of the drainage
lines and the locations of the principal towns see Figs. 20 and 204.]

SCHISTS AND SILURIAN SLATES[50]

The oldest series of rocks along the seventy-third meridian of Peru
extends eastward from the Vilcapampa batholith nearly to the border of
the Cordillera, Fig. 157. It consists of (1) a great mass of slates and
shales with remarkable uniformity of composition and structure over
great areas, and (2) older schists and siliceous members in restricted
belts. They are everywhere thoroughly jointed; near the batholith they
are also mineralized and altered from their original condition; in a few
places they have been intruded with dikes and other form of igneous
rock.

The slates and shales underlie known Carboniferous strata on their
eastern border and appear to be a physical continuation of the
fossiliferous slates of Bolivia; hence they are provisionally referred
to the Silurian, though they may possibly be Devonian. Certainly the
known Devonian exceeds in extent the known Silurian in the Central Andes
but its lithological character is generally quite unlike the character
of the slates here referred to the Silurian. The schists are of great
but unknown age. They are unconformably overlain by known Carboniferous
at Puquiura in the Vilcapampa Valley (Fig. 158), and near Chuquibambilla
on the opposite side of the Cordillera Vilcapampa. The deeply weathered
fissile mica schists east of Pasaje (see Appendix C for all locations)
are also unconformably overlain by conglomerate and sandstone of
Carboniferous age. While the schists vary considerably in lithological
appearance and also in structure, they are everywhere the lowest rocks
in the series and may with confidence be referred to the early
Palaeozoic, while some of them may date from the Proteriozoic.

[Illustration: FIG. 158--Geologic sketch map of the lower Urubamba
Valley. A single traverse was made along the valley, hence the
boundaries are not accurate in detail. They were sketched in along a few
lateral traverses and also inferred from the topography. The country
rock is schist and the granite intruded in it is an arm of the main
granite mass that constitutes the axis of the Cordillera Vilcapampa. The
structure and to some degree the extent of the sandstone on the left are
represented in Figs. 141 and 142.]

The Silurian beds are composed of shale, sandstone, shaly sandstone,
limestone, and slate with some slaty schist, among which the shales are
predominent and the limestones least important. Near their contact with
the granite the slate series is composed of alternating beds of
sandstone and shale arranged in beds from one to three feet thick. At
Santa Ana they become more fissile and slaty in character and in several
places are quarried and used for roofing. At Rosalina they consist of
almost uniform beds of shale so soft and so minutely and thoroughly
jointed as to weather easily. Under prolonged erosion they have,
therefore, given rise to a well-rounded and soft-featured landscape.
Farther down the Urubamba Valley they again take on the character of
alternating beds of sandstone and shale from a few feet to fifteen and
more feet thick. In places the metamorphism of the series has been
carried further--the shales have become slates and the sandstones have
been altered to extremely resistant quartzites. The result is again
clearly shown in the topography of the valley wall which becomes bold,
inclosing the river in narrow “pongos” or canyons filled with huge
bowlders and dangerous rapids. The hills become mountains, ledges
appear, and even the heavy forest cover fails to smooth out the natural
ruggedness of the landscape.

It is only upon their eastern border that the Silurian series includes
calcareous beds, and all of these lie within a few thousand yards of the
contact with the Carboniferous limestones and shales. At first they are
thin paper-like layers; nearer the top they are a few inches wide and
finally attain a thickness of ten or twelve feet. The available
limestone outcrops were rigorously examined for fossils but none were
found, although they are lavishly distributed throughout the younger
Carboniferous beds just above them. It is also remarkable that though
the Silurian age of these beds is reasonably inferred they are not
separated from the Carboniferous by an unconformity, at least we could
find none in this locality. The later beds disconformably overlie the
earlier beds, although the sharp differences in lithology and fossils
make it easy to locate the line of separation. The limestone beds of the
Silurian series are extremely compact and unfossiliferous. At least in
this region those of Carboniferous age are friable and the fossils
varied and abundant. The Silurian beds are everywhere strongly inclined
and throughout the eastern half or third of their outcrop in the
Urubamba Valley they are nearly vertical.

In view of the enormous thickness of the repeated layers of shale and
sandstone this series is of great interest. Added importance attaches to
their occurrence in a long belt from the eastern edge of the Bolivian
highlands northward through Peru and possibly farther. From the fact
that their disturbance has been on broad lines over wide areas with
extreme metamorphism, they are to be separated from the older
mica-schists and the crumpled chlorite schists of Puquiura and Pasaje.
Further reasons for this distinction lie in their lithologic difference
and, to a more important degree, in the strong unconformity between the
Carboniferous and the schists in contrast to the disconformable
relations shown between the Carboniferous and Silurian fifty miles away
at Pongo de Mainique. The mashing and crumpling that the schists have
experienced at Puquiura is so intense, that were they a part of the
Silurian series the latter should exhibit at least a slight unconformity
in relation to the Carboniferous limestones deposited upon them.

If our interpretation of the relation of the schists to the slates and
shales be correct, we should have a mountain-making period introduced in
pre-Silurian time, affecting the accumulated sediments and bringing
about their metamorphism and crumpling on a large scale. From the
mountains and uplands thus created on the schists, sediments were washed
into adjacent waters and accumulated as even-bedded and extensive sheets
of sands and muds (the present slates, shales, quartzites, etc.).
Nowhere do the sediments of the slate series show a conglomeratic phase;
they are remarkably well-sorted and consist of material disposed with
great regularity. Though they are coarsest at the bottom the lower beds
do not show cross-bedding, ripple marking, or other signs of
shallow-water conditions. Toward the upper part of the series these
features, especially the ripple-marking, make their appearance. During
the deposition of the last third of the series, and again just before
the deposition of the limestone, the beds took on a predominantly
arenaceous character associated with ripple marks and cross-bedding
characteristic of shallow-water deposits.

In the persistence of arenaceous sediments throughout the series and the
distribution of the ripple marks through the upper third of the beds, we
have a clear indication that the degree of shallowness was sufficient to
bring the bottom on which the sediments accumulated into the zone of
current action and possibly wave action. It is also worth considering
whether the currents involved were not of similar origin to those now a
part of the great counter-clockwise movements in the southern seas. If
so, their action would be peculiarly effective in the wide distribution
of the sediment derived from a land mass on the eastern edge of a
continental coast, since they would spread out the material to a greater
and greater degree as they flowed into more southerly latitudes. Among
geologic agents a broad ocean current of relatively uniform flow would
produce the most uniform effects throughout a geologic period, in which
many thousand feet of clastic sediments were being accumulated. A
powerful ocean current would also work on flats (in contrast to the
gradient required by near-shore processes), and at the same time be of
such deep and steady flow as to result in neither ripple marks nor
cross-bedding.

The increasing volume of shallow-water sediments of uniform character
near the end of the Silurian, indicates great crustal stability at a
level which brought about neither a marked gain nor loss of material to
the region. At any rate we have here no Devonian sediments, a
characteristic shared by almost all the great sedimentary formations of
Peru. At the beginning of the Carboniferous the water deepened, and
great heavy-bedded limestones appear with only thin shale partings
through a vertical distance of several hundreds of feet. The enormous
volume of Silurian sediments indicates the deep and prolonged erosion of
the land masses then existing, a conclusion further supported (1) by the
extensive development of the Silurian throughout Bolivia as well as
Peru, (2) by the entire absence of coarse material whether at the top or
bottom of the section, and (3) by the very limited extent of older rock
now exposed even after repeated and irregular uplift and deep
dissection. Indeed, from the latter very striking fact, it may be
reasonably argued that in a general way the relief of the country was
reduced to sea level at the close of the Silurian. Over the perfected
grades of that time there would then be afforded an opportunity for the
effective transportation of waste to the extreme limits of the land.

Further evidence of the great reduction of surface during the Silurian
and Devonian is supplied by the extensive development of the
Carboniferous strata. Their outcrops are now scattered across the higher
portions of the Andean Cordillera and are prevailingly calcareous in
their upper portions. Upon the eastern border of the Silurian they
indicate marine conditions from the opening of the period, but at Pasaje
in the Apurimac Valley they are marked by heavy beds of basal
conglomerate and sandstone, and an abundance of ripple marking and other
features associated with shallow-water and possibly near-shore
conditions.

CARBONIFEROUS

Carboniferous strata are distributed along the seventy-third meridian
and rival in extent the volcanic material that forms the western border
of the Andes. They range in character from basal conglomerates,
sandstones, and shales of limited development, to enormous beds of
extremely resistant blue limestone, in general well supplied with
fossils. On the eastern border of the Andes they are abruptly terminated
by a great fault, the continuation northward of the marginal fault
recognized in eastern Bolivia by Minchin[51] and farther north by the
writer.[52] Coarse red sandstones with conglomeratic phase abut sharply
and with moderate inclination against almost vertical sandstones and
limestones of Carboniferous age. The break between the vertical
limestones and the gently inclined sandstones is marked by a prominent
scarp nearly four thousand feet high (Fig. 159), and the limestone
itself forms a high ridge through which the Urubamba has cut a narrow
gateway, the celebrated Pongo de Mainique.

[Illustration: FIG. 159--Topographic and structural section at the
northeastern border of the Peruvian Andes. The slates are probably
Silurian, the fossiliferous limestones are known Carboniferous, and the
sandstones are Tertiary grading up to Pleistocene.]

At Pasaje, on the western side of the Apurimac, the Carboniferous again
appears resting upon the old schists described on p. 236. It is steeply
upturned, in places vertical, is highly conglomeratic, and in a belt a
half-mile wide it forms true badlands topography. It is succeeded by
evenly bedded sandstones of fine and coarse composition in alternate
beds, then follow shales and sandstones and finally the enormous beds of
limestone that characterize the series. The structure is on the whole
relatively simple in this region, the character and attitude of the beds
indicating their accumulation in a nearly horizontal position. Since the
basal conglomerate contains only pebbles and stones derived from the
subjacent schists and does not contain granites like those in the
Cordillera Vilcapampa batholith on the east it is concluded that the
batholithic invasion was accompanied by the compression and tilting of
the Carboniferous beds and that the batholith itself is
post-Carboniferous. From the ridge summits above Huascatay and in the
deep valleys thereabouts the Carboniferous strata may be seen to extend
far toward the west, and also to have great extent north and south.
Because of their dissected, bare, and, therefore, well-exposed condition
they present exceptional opportunities for the study of Carboniferous
geology in central Peru.

[Illustration: FIG. 160--The deformative effects of the granite
intrusion of the Cordillera Vilcapampa are here shown as transmitted
through ancient schists to the overlying conglomerates, sandstones, and
limestones of Carboniferous age, in the Apurimac Valley at Pasaje.]

Carboniferous strata again appear at Puquiura, Vilcapampa, and
Pampaconas. They are sharply upturned against the Vilcapampa batholith
and associated volcanic material, chiefly basalt, porphyry, and various
tuffs and related breccias. The Carboniferous beds are here more
arenaceous, consisting chiefly of alternating beds of sandstone and
shale. The lowermost beds, as at Pongo de Mainique, are dominantly
marine, fossiliferous limestone beds having a thickness estimated to be
over two miles.

From Huascatay westward and southward the Carboniferous is in part
displaced by secondary batholiths of granite, in part cut off or crowded
aside by igneous intrusions of later date, and in still larger part
buried under great masses of Tertiary volcanic material. Nevertheless,
it remains the dominating rock type over the whole stretch of country
from Huascatay to Huancarama. In the northwestern part of the Abancay
sheet its effect on the landscape may be observed in the knife-like
ridge extending from west to east just above Huambo. Above
Chuquibambilla it again outcrops, resting upon a thick resistant
quartzite of unknown age, Fig. 162. It is strongly developed about
Huadquirca and Antabamba and, still associated with a quartzite floor,
it finally disappears under the lavas of the great volcanic field on the
western border of the Andes. Figs. 141 and 142 show its relation to the
invading granite batholiths and Fig. 162 shows further structural
features as developed about Antabamba where the great volcanic field of
the Maritime Cordillera begins.

[Illustration: FIG. 161--Types of deformation north of Lambrama near
Sotospampa. A dark basaltic rock has invaded both granite-gneiss and
slate. Sills and dikes occur in great numbers. The topographic
depression in the profile is the Lambrama Valley. See the Lambrama
Quadrangle.]

Both the enormous thickness of the Carboniferous limestone series and
the absence of clastic members over great areas in the upper portion of
the series prove the widespread extent of the Carboniferous seas and
their former occurrence in large interlimestone tracts from which they
have since been eroded. At Puquiura they extend far over the schist, in
fact almost completely conceal it; at Pasaje they formerly covered the
mica-schists extensively, their erosion in both cases being conditioned
by the pronounced uplift and marginal deformation which accompanied the
development of the Vilcapampa batholith.

[Illustration: FIG. 162--Sketch sections at Antabamba to show (a)
deformed limestones on the upper edge of the geologic map, Fig. 163 A;
and (b) the structural relations of limestone and quartzite. See also
Fig. 163.]

The degree of deformation of the Carboniferous sediments varies between
simple uplift through moderate folding and complex disturbances
resulting in nearly vertical attitudes. The simplest structures are
represented at Pasaje, where the uplift of the intruded schists,
marginal to the Vilcapampa batholith, has produced an enormous
monoclinal fold exposing the entire section from basal conglomerates and
sandstones to the thickest limestone. Above Chuquibambilla the
limestones have been uplifted and very gently folded by the invasion of
granite associated with the main batholith and several satellitic
batholiths of limited extent. A higher degree of complexity is shown at
Pampaconas (Fig. 141), where the main monoclinal fold is traversed
almost at right angles by secondary folds of great amplitude. The
limestones are there carried to the limit of the winter snows almost at
the summit of the Cordillera. The crest of each secondary anticline
rises to form a group of conspicuous peaks and tabular ridges. Higher in
the section, as at Puquiura, the sandstones are thrown into a series of
huge anticlines and synclines, apparently by the marginal compression
brought about at the time of the intrusion of the granite core of the
range. At Pongo de Mainique the whole of the visible Carboniferous is
practically vertical, and is cut off by a great fault marking the abrupt
eastern border of the Cordillera.

[Illustration: FIG. 163--Geologic sketch section to show the relation of
the volcanic flows of Fig. 164 to the sandstones and quartzites
beneath.]

It is noteworthy that the farther east the Carboniferous extends the
more dominantly marine it becomes, though marine beds of great thickness
constitute a large part of the series in whatever location. From
Huascatay westward the limestones become more and more argillaceous, and
finally give way altogether to an enormous thickness of shales,
sandstones, and thin conglomerates. These were observed to extend with
strong inclination westward out of the region studied and into and under
the volcanoes crowning the western border of the Cordillera. Along the
line of traverse opportunity was not afforded for further study of this
aspect of the series, since our route led generally along the strike
rather than along the dip of the beds. It is interesting to note,
however, that these observations as to the increasing amounts of clastic
material in a westward direction were afterwards confirmed by Señor José
Bravo, the Director of the Bureau of Mines at Lima, who had found
Carboniferous land plants in shales at Pacasmayo, the only fossils of
their kind found in Peru. Formerly it had been supposed that non-marine
Carboniferous was not represented in Peru. From the varied nature of the
flora, the great thickness of the shales in which the specimens were
collected, and the fact that the dominantly marine Carboniferous
elsewhere in Peru is of great extent, it is concluded that the land upon
which the plants grew had a considerable area and probably extended far
west of the present coast line. Since its emergence it has passed
through several orogenic movements. These have resulted in the uplift of
the marine portion of the Carboniferous, while the terrestrial deposits
seem to have all but disappeared in the down-sunken blocks of the ocean
floor, west of the great fault developed along the margin of the
Cordillera. The following figures are graphic representations of this
hypothesis.

[Illustration: FIG. 164--Geologic sketch map and section, Antabamba
region. The Antabamba River has cut through almost the entire series of
bedded strata].

[Illustration: FIG. 165--The upper diagram (A) represents the
hypothetical distribution of land and sea during the Carboniferous
Period, as inferred from the present distribution and character of
Carboniferous limestones and slates. The lower diagram (B) represents
the present relief. The dotted line at the left of the two diagrams
connects identical points. The fragmentation of the former continental
border is believed to have left only a small portion of a former coastal
chain and to have been contemporaneous with the development of ocean
abysses near the present shore.]

The wide distribution of the Carboniferous sediments and especially the
limestones, together with the uniformity of the fossil faunas, makes it
certain that the sea extended entirely across the region now occupied
by the Andes. However, from the relation of the Carboniferous to the
basal schists, and the most conservative extension of the known
Carboniferous, it may be inferred that the Carboniferous sea did not
completely cover the entire area but was broken here and there by island
masses in the form of an elongated archipelago. The presence of land
plants in the Carboniferous of Pisco warrants the conclusion that a
second island mass, possibly an island chain parallel to the first,
extended along and west of the present shore.

CRETACEOUS

The Cretaceous formations are of very limited extent in the belt of
country under consideration, in spite of their generally wide
distribution in Peru. They are exposed distinctly only on the western
border of the Cordillera and in special relations. In the gorge of
Cotahuasi, over seven thousand feet deep, about two thousand feet of
Cretaceous limestones are exposed. The series includes only a very
resistant blue limestone and terminates abruptly along a well-marked and
highly irregular erosion surface covered by almost a mile of volcanic
material, chiefly lava flows. The character of the bottom of the section
is likewise unknown, since it lies apparently far below the present
level of erosion.

[Illustration: FIG. 166--Geologic sketch map and cross-section in the
Cotahuasi Canyon at Cotahuasi. With a slight gap this figure continues
Fig. 167 to the left. The section represents a spur of the main plateau
about 1,500 feet high in the center of the map.]

The Cretaceous limestones of the Cotahuasi Canyon are everywhere greatly
and irregularly disturbed. Typical conditions are represented in the
maps and sections, Figs. 166 and 167. They are penetrated and tilted by
igneous masses, apparently the feeders of the great lava sheets that
form the western summit of the Cordillera. From the restricted
development of the limestones along a western border zone it might be
inferred that they represent a very limited marine invasion. It is
certainly clear that great deformative movements were in progress from
at least late Palæozoic time since all the Palæozoic deposits are broken
abruptly down in this direction, and, except for such isolated
occurrences as the land Carboniferous at Pacasmayo, are not found
anywhere in the coastal region today. The Cretaceous is not only limited
within a relatively narrow shore zone, but also, like the Palæozoic, it
is broken down toward the west, not reappearing from beneath the
Tertiary cover of the desert region or upon the granite-gneisses that
form the foundation for all the known sedimentary strata of the
immediate coast.

[Illustration: FIG. 167--Geologic sketch map and cross-section in the
Cotahuasi Canyon at Taurisma, above Cotahuasi. The relations of
limestone and lava flows in the center of the map and on a spur top near
the canyon floor. Thousands of feet of lava extend upward from the flows
that cap the limestone.]

From these considerations I think we have a strong suggestion of the
geologic date assignable to the development of the great fault that is
the most strongly marked structural and physiographic feature of the
west coast of South America. Since the development of this fault is so
intimately related to the origin of the Pacific Ocean basin its study is
of special importance. The points of chief interest may be summarized as
follows:

(1) The character of the land Carboniferous implies a much greater
extent of the land than is now visible.

(2) The progressive coarsening of the Carboniferous deposits westward
and their land derivation, together with the great thickness of the
series, point to an elevated land mass in process of erosion west of
the series as a whole, that is west of the present coast.

(3) The restricted development of the Cretaceous seas upon the western
border of the Carboniferous, and the still more restricted development
of the Tertiary deposits between the mountains and the present coast,
point to increasing definition of the submarine scarp through the
Mesozoic and the Tertiary.

(4) The Tertiary deposits are all clearly derived from the present
mountains and have been washed seaward down slopes with geographic
relations approximately like those of the present.

(5) From the great width, deep dissection, and subsequent burial of the
Tertiary terraces of the coast, it is clear that the greater part of the
adjustment of the crust to which the bordering ocean basin is due was
accomplished at least by mid-Tertiary time.

[Illustration: FIG. 168--Composite structure section representing the
succession of rocks in the Urubamba Valley from Urubamba to Torontoy.]

Aside from the fossiliferous limestones of known Cretaceous age there
have been referred to the Cretaceous certain red sandstones and shales
marked, especially in the central portions of the Cordillera, by the
presence of large amounts of salt and gypsum. These beds were at first
considered Permian, but Steinmann has since found at Potosí related and
similar formations with Cretaceous fossils. In this connection it is
also necessary to add that the great red sandstone series forming the
eastern border of the Andes in Bolivia is of uncertain age and has
likewise been referred to the Cretaceous, though the matter of its age
has not yet been definitely determined. In 1913 I found it appearing in
northwestern Argentina in the Calchaquí Valley in a relation to the main
Andean mass, similar to that displayed farther north. It contains
fossils and its age was, therefore, readily determinable there.[53]

In the Peruvian field the red beds of questionable age were not examined
in sufficient detail to make possible a definite age determination. They
occur in a great and only moderately disturbed series in the Anta basin
north of Cuzco, but are there not fossiliferous. The northeastern side
of the hill back of Puqura (of the Anta basin: to be distinguished from
Puquiura in the Vilcabamba Valley) is composed largely of rocks of this
class. In a few places their calcareous members have been weathered out
in such a manner as to show karst topography. Where they occur on the
well-drained brow of a bluff the caves are used in place of houses by
Indian farmers. The large and strikingly beautiful Lake Huaipo, ten
miles north of Anta, and several smaller, neighboring lakes, appear to
have originated in solution depressions formed in these beds.

[Illustration: FIG. 169--The line of unconformity between the igneous
basement rocks (agglomerates at this point) and the quartzites and
sandstones of the Urubamba Valley, between the town of Urubamba and
Ollantaytambo.]

[Illustration: FIG. 170--The inclined lower and horizontal upper
sandstone on the southeastern wall of the Majes Valley at Hacienda
Cantas. The section is a half-mile high.]

The structural relation of the red sandstone series to the older rocks
is well displayed about half-way between Urubamba and Ollantaytambo in
the deep Urubamba Valley. The basal rocks are slaty schist and granite
succeeded by agglomerates and basalt porphyries upon whose eroded
surfaces (Fig. 169) are gray to yellow cross-bedded sandstones. Within a
few hundred feet of the unconformity gypsum deposits begin to appear and
increase in number to such an extent that the resulting soil is in
places rendered worthless. Copper-stained bands are also common near the
bottom of the series, but these are confined to the lower beds. Higher
up in the section, for example, just above the gorge between Urubamba
and Ollantaytambo, even-bedded sandstones occur whose most prominent
characteristic is the regular succession of coarse and fine sandstone
beds. Such alternations of character in sedimentary rocks are commonly
marked by alternating shales and sandstones, but in this locality shales
are practically absent. Toward the top of the section gypsum deposits
again appear first as beds and later, as in the case of the hill-slope
on the southern shore of Lake Huaipo, as veins and irregular masses of
gypsum. The top of the deformed Cretaceous (?) is eroded and again
covered unconformably by practically flat-lying Tertiary deposits.

TERTIARY

The Tertiary deposits of the region under discussion are limited to
three regions: (1) the extreme eastern border of the main Cordillera,
(2) intermontane basins, the largest and most important of which are (a)
the Cuzco basin and (b) the Titicaca-Poopó basin on the
Peruvian-Bolivian frontier, and (3) in the west-coast desert and in
places upon the huge terraces that form a striking feature of the
topography of the coast of Peru.

It has already been pointed out that the eastern border of the
Cordillera is marked by a fault of great but undetermined throw, whose
topographic importance may be estimated from the fact that even after
prolonged erosion it stands nearly four thousand feet high. Cross-bedded
and ripple-marked features and small lenses of conglomerate are common.
The beds now dip at an angle approximately 20° to 50° northward at the
base of the scarp, but have decreasing dip as they extend farther north
and east. It is noteworthy that the deposits become distinctly
conglomeratic as flatter dips are attained, and that there seems to have
been a steady accumulation of detrital material from the mountains for a
long period, since the deposits pass in unbroken succession from the
highly indurated and massive beds of the mountain base to loose
conglomerates that now weather down much like an ordinary gravel bank.
In a few places just below the mouth of the Ticumpinea, logs about six
inches in diameter were observed embeded in the deposits, but these
belong distinctly to the upper horizons.

The border deposits, though they vary in dip from nearly flat to 50°,
are everywhere somewhat inclined and now lie up to several hundred feet
above the level of the Urubamba River. Their upper surface is moderately
dissected, the degree of dissection being most pronounced where the dips
are steepest and the height greatest. In fact, the attitude of the
deposits and their progressive change in character point toward, if they
do not actually prove, the steady and progressive character of the beds
first deposited and their erosion and redeposition in beds now higher in
the series.

Upon the eroded upper surfaces of the inclined border deposits, gravel
beds have been laid which, from evidence discussed in a later paragraph,
are without doubt referable to the Pleistocene. These in turn are now
dissected. They do not extend to the highest summits of the deformed
beds but are confined, so far as observations have gone, to elevations
about one hundred feet above the river. From the evidence that the
overlying horizontal beds are Pleistocene, the thick, inclined beds are
referred to Tertiary age, though they are nowhere fossiliferous.

Observations along the Urubamba River were extended as far northward as
the mouth of the Timpia, one of the larger tributaries. Upon returning
from this point by land a wide view of the country was gained from the
four-thousand-foot ridge of vertical Carboniferous limestone, in which
it appeared that low and irregular strike ridges continue the features
of the Tertiary displayed along the mountain front far northward as well
as eastward, to a point where the higher ridges and low mountains of
older rock again appear--the last outliers of the Andean system in Peru.
Unfortunately time enough was not available for an extension of the trip
to these localities whose geologic characters still remain entirely
unknown. From the topographic aspects of the country, it is, however,
reasonably certain that the whole intervening depression between these
outlying ranges and the border of the main Cordillera, is filled with
inclined and now dissected and partly covered Tertiary strata. The
elevation of the upper surface does not, however, remain the same; it
appears to decrease steadily and the youngest Tertiary strata disappear
from view below the sediments of either the Pleistocene or the present
river gravels. In the more central parts of the depression occupied by
the Urubamba Valley, only knobs or ridges project here and there above
the general level.

_The Coastal Tertiary_

The Tertiary deposits of the Peruvian desert region southwest of the
Andes have many special features related to coastal deformation, changes
of climate, and great Andean uplifts. They lie between the west coast of
Peru at Camaná and the high, lava-covered country that forms the western
border of the Andes and in places are over a mile thick. They are
non-fossiliferous, cross-bedded, ripple-marked, and have abundant lenses
of conglomerate of all sizes. The beds rest upon an irregular floor
developed upon a varied mass of rocks. In some places the basement
consists of old strata, strongly deformed and eroded. In other places it
consists of a granite allied in character and probably in origin with
the old granite-gneiss of the Coast Range toward the west. Elsewhere the
rock is lava, evidently the earliest in the great series of volcanic
flows that form this portion of the Andes.

The deposits on the western border of the Andes are excellently exposed
in the Majes Valley, one of the most famous in Peru, though its fame
rests rather upon the excellence and abundance of its vineyards and
wines than its splendid geologic sections. Its head lies near the base
of the snow-capped peaks of Coropuna; its mouth is at Camaná on the
Pacific, a hundred miles north of Mollendo. It is both narrow and deep;
one may ride across its floor anywhere in a half hour. In places it is a
narrow canyon. Above Cantas it is sunk nearly a mile below the level of
the desert upland through which it flows. Along its borders are exposed
basal granites, old sedimentaries, and lavas; inter-bedded with it are
other lavas that lie near the base of the great volcanic series; through
it still project the old granites of the Coast Range; and upon it have
been accumulated additional volcanic rocks, wind-blown deposits, and,
finally, coarse wash formed during the glacial period. From both the
variety of the formations, the small amount of marginal dissection, and
the excellent exposures made possible by the deep erosion and desert
climate, the Majes Valley is one of the most profitable places in Peru
for physiographic and geologic study.

[Illustration: FIG. 171--Generalized sketch section to show the
structural relations of the Maritime Cordillera, the desert pampas, and
the Coast Range.]

The most complete succession of strata (Tertiary) occurs just below
Cantas on the trail to Jaguey (Fig. 171). Upon a floor of
granite-gneiss, and alternating beds of quartzite and shale belonging to
an older series, are deposited heavy beds of red sandstone with many
conglomerate lenses. The sandstone strata are measurably deformed and
their upper surfaces moderately dissected. Upon them have been deposited
unconformably a thicker series of deposits, conglomerates, sandstones,
and finer wind-blown material. The basal conglomerate is very
coarse--much like beach material in both structure and composition, and
similar to that along and south of the present coast at Camaná. Higher
in the section the material is prevailingly sandy and is deposited in
regular beds from a few inches to a few feet in thickness. Near the top
of the section are a few hundred feet of strata chiefly wind deposited.
Unconformably overlying the whole series and in sharp contrast to the
fine wind-blown stuff below it, is a third series of coarse deposits
about five hundred feet thick. The topmost material, that forming the
surface of the desert upland, consists of wind-blown sand now shifted by
the wind and gathered into sand dunes or irregular drifts, banks of
white earth, “tierra blanca,” and a pebble pavement a few inches thick.

If the main facts of the above section are now summarized they will
facilitate an understanding of other sections about to be described,
inasmuch as the summary will in a measure anticipate our conclusions
concerning the origin of the deposits and their subsequent history. The
sediments in the Majes Valley between Cantas and Jaguey consist of three
series separated by two unconformities. The lowermost series is evenly
bedded and rather uniform in composition and topographic expression,
standing forth in huge cliffs several hundred feet high on the eastern
side of the valley. This lower series is overlain by a second series,
which consists of coarse conglomerate grading into sand and ultimately
into very fine fluffy wind-deposited sands and silts. The lower series
is much more deformed than the upper, showing that the deforming
movements of later geologic times have been much less intense than the
earlier, as if there had been a fading out or weakening of the deforming
agents. Finally there is a third series several hundred feet thick which
forms the top of the section.

[Illustration: FIG. 172--Geologic relations of Coast Range, desert
deposits, and Maritime Cordillera at Moquegua, Peru. After G. I. Adams;
Bol. de Minas del Perú, Vol. 2, No. 4, 1906, p. 20.]

[Illustration: FIG. 173--Sketch section to show structural details on
the walls of the Majes Valley near Aplao, looking south.]

Three other sections may now be examined, one immediately below Cantas,
one just above, and one opposite Aplao. The section below Cantas is
shown in Fig. 173, and indicates a lower series of red sandstones
crossed by vertical faults and unconformably overlain by nearly
horizontal conglomerates, sandstones, etc., and the whole faulted again
with an inclined fault having a throw of nearly 25°. A white to gray
sandstone unconformably overlying the red sandstone is shown
interpolated between the lowermost and uppermost series, the only
example of its kind, however. No important differences in
lithographical character may be noted between these and the beds of the
preceding section.

Again just above Cantas on the east side of the valley is a clean
section exposing about two thousand feet of strata in a half mile of
distance. The foundation rocks are old quartzites and shales in
regularly alternating beds. Upon their uneven upper surfaces are several
thousand feet of red sandstones and conglomerates, which are both folded
and faulted with the underlying quartzites. Above the red sandstones is
a thick series of gray sandstones and silts which makes the top of the
section and unconformably overlies the earlier series.

A similar succession of strata was observed at Aplao, still farther up
the Majes Valley, Fig. 174. A greatly deformed and metamorphosed older
series is unconformably overlaid by a great thickness of younger strata.
The younger strata may be again divided into two series, a lower series
consisting chiefly of red sandstones and an upper consisting of gray to
yellow, and only locally red sands of finer texture and more uniform
composition. The two are separated by an erosion surface and only the
upper series is tilted regionally seaward with faint local deformation;
the lower series is both folded and faulted with overthrusts aggregating
several thousand feet of vertical and a half mile of horizontal
displacement.

[Illustration: FIG. 174--The structural relations of the strata on the
border of the Majes Valley at Aplao, looking west. Field sketch from
opposite side of valley. Height of section about 3,000 feet; length
about ten miles.]

The above sections all lie on the eastern side of the Majes Valley. From
the upper edge of the valley extensive views were gained of the strata
on the opposite side, and two sections, though they were not examined at
close range, are at least worth comparing with those already given. From
the narrows below Cantas the structure appears as in Figs. 175-176, and
shows a deforming movement succeeded by erosion in a lower series. The
upper series of sedimentary rock has suffered but slight deformation. A
still more highly deformed basal series occurs on the right of the
section, presumably the older quartzites. At Huancarqui, opposite Aplao,
an extensive view was gained of the western side of the valley, but the
lower Tertiary seems not to be represented here, as the upper undeformed
series rests unconformably upon a tilted series of quartzites and
slates. Farther up the Cantas valley (an hour’s ride above Aplao) the
Tertiary rests upon volcanic flows or older quartzites or the
granite-gneiss exposed here and there along the valley floor.

[Illustration: FIG. 175--Sketch section to show the structural details
of the strata on the south wall of the Majes Valley near Cantas. The
section is two miles long.]

[Illustration: FIG. 176--Composite geologic section to show the
structural relations of the rocks on the western border of the Maritime
Cordillera. The inclined strata at the right bottom represent older
rocks; in places igneous, in other places sedimentary.]

In no part of the sedimentaries in the Majes Valley were fossils found,
save in the now uplifted and dissected sands that overlie the upraised
terraces along the coast immediately south of Camaná and also back of
Mollendo. Like similar coastal deposits elsewhere along the Peruvian
littoral, the terrace sands are of Pliocene or early Pleistocene age.
The age of the deposits back of the Coast Range is clearly greater than
that of the coastal deposits, (1) since they involve two unconformities,
a mile or more of sediments, and now stand at least a thousand feet
above the highest Pliocene (or Pleistocene) in the Camaná Valley, and
(2) because the erosion history of the interior sediments may be
correlated with the physiographic history of the coastal terraces and
the correlation shows that uplift and dissection of the terraces and of
the interior deposits went hand in hand, and that the deposits on the
terraces may similarly be correlated with alluvial deposits in the
valley.

We shall now see what further ground there is for the determination of
the age of these sediments. Just below Chuquibamba, where they first
appear, the sediments rest upon a floor of volcanic and older rock
belonging to the great field now known from evidence in many localities
to have been formed in the early Tertiary, and here known to be
post-Cretaceous from the relations between Cretaceous limestones and
volcanics in the Cotahuasi Valley (see p. 247). Although volcanic flows
were noted interbedded with the desert deposits, these are few in
number, insignificant in volume, and belong to the top of the volcanic
series. The same may be said of the volcanic flows that locally overlie
the desert deposits. We have then definite proof that the sandstones,
conglomerates, and related formations of the Majes Valley and bordering
uplands are older than the Pliocene or early Pleistocene and younger
than the Cretaceous and the older Tertiary lavas. Hence it can scarcely
be doubted that they represent a considerable part of the Tertiary
period, especially in view of the long periods of accumulation which the
thick sediments represent, and the additional long periods represented
by the two well-marked unconformities between the three principal groups
of strata.

If we now trace the physical history of the region we have first of all
a deep depression between the granite range along the coast and the
western flank of the Andes. Here and there, as in the Vitor, the Majes,
and other valleys, there were gaps through the Coast Range. Nowhere did
the relief of the coastal chain exceed 5,000 feet. The depression had
been partly filled in early geologic (probably early Paleozoic) time by
sediments later deformed and metamorphosed so that they are now
quartzites and shales. The greater resistance of the granite of the
Coast Range resulted in superior relief, while the older deformed
sedimentaries were deeply eroded, with the result that by the beginning
of the Tertiary the basin quality of the depression was again
emphasized. All these facts are expressed graphically in Fig. 171. On
the western flanks of the granite range no corresponding sedimentary
deposits are found in this latitude. The sea thus appears to have stood
farther west of the Coast Range in Paleozoic times than at present.

[Illustration: FIG. 177--Composite structure section at Aplao.]

For the later history it is necessary to assemble the various Tertiary
sections described on the preceding pages. First of all we recognize
three quite distinct types of accumulations, for which we shall have to
postulate three sets of conditions and possibly three separate agents.
The first or lowermost consists of even-bedded deposits of red and gray
sandstones, the former color predominating. The material is in general
well-sorted save locally, where lenses and even thin beds of
conglomerate have been developed. There is, however, about the whole
series a uniformity and an orderliness in striking contrast to the
coarse, cross-bedded, and irregular material above the unconformity. On
their northeastern or inner margin the sandstones are notably coarser
and thicker, a natural result of proximity to the mountains, the source
of the material. The general absence of wind-blown deposits is marked;
these occur entirely along the eastern and northern portions of the
deposits and are recognized (1) by their peculiar cross-bedding, and (2)
by the fact that the cross-bedding is directed northeastward in a
direction contrary to the regional dip of the series, a condition
attributable to the strong sea breezes that prevail every afternoon in
this latitude.

The main body of the material is such as might be deposited on the wide
flood plains of piedmont streams during a period of prolonged erosion
on surrounding highlands that served as the feeding grounds of the
streams. The alternations in the character of the deposits, alternations
which, in a general view, give a banded appearance to the rock, are
produced by successions of beds of fine and coarse material, though all
of it is sandstone. Such successions are probably to be correlated with
seasonal changes in the volume and load of the depositing streams.

To gain an idea of the conditions of deposition we may take the
character of the sediments as described above, and from them draw
deductions as to the agents concerned and the manner of their action.

We may also apply to the area the conclusions drawn from the study of
similar deposits now in process of formation. We have between the coast
ranges of northern Chile and the western flanks of the Cordillera
Sillilica, probably the best example of piedmont accumulation in a dry
climate that the west coast of South America affords.

Along the inner edge of the Desert of Tarapacá, roughly between the
towns of Tarapacá and Quillagua, Chile, the piedmont gravels, sands,
silts, and muds extend for over a hundred miles, flanking the western
Andes and forming a transition belt between these mountains and the
interior basins of the coast desert. The silts and muds constitute the
outer fringe of the piedmont and are interrupted here and there where
sands are blown upon them from the higher portions of the piedmont, or
from the desert mountains and plains on the seaward side. Practically no
rain falls upon the greater part of the desert and the only water it
receives is that borne to it by the piedmont streams in the early
summer, from the rains and melted snows of the high plateau and
mountains to the eastward. These temporary streams spread upon the outer
edge of the piedmont a wide sheet of mud and silt which then dries and
becomes cracked, the curled and warped plates retaining their character
until the next wet season or until covered with wind-blown sand. The
wind-driven sand fills the cracks in the muds and is even drifted under
the edges of the upcurled plates, filling the spaces completely. Over
this combined fluvial and æolian deposit is spread the next layer of
mud, which frequently is less extensive than the earlier deposits, thus
giving abundant opportunity for the observation of the exact manner of
burial of the older sand-covered stratum.

Now while the alternations are as marked in Peru as in Chile, it is
noteworthy that the Tertiary material in Peru is not only coarse
throughout, even to the farthest limits of the piedmont, but also that
the alternating beds are thick. Moreover, there are only the most feeble
evidences of wind action in the lowermost Tertiary series. I was
prepared to find curled plates, wind-blown sands, and muds and silts,
but they are almost wholly absent. It is, therefore, concluded that the
dryness was far less extreme than it is today and that full streams of
great competency flowed vigorously down from the mountains and carried
their loads to the inner border of the Coast Range and in places to the
sea.

The fact that the finer material is _sandy_, not clayey or silty, that
it almost equals in thickness the coarser layers, and that its
distribution appears to be co-extensive with the coarser, warrants the
conclusion that it too was deposited by competent streams of a type far
different from the withering streams associated with piedmont deposits
in a thoroughly arid climate like that of today. Both in the second
Tertiary series and on the present surface are such clear examples of
deposits made in a drier climate as to leave little doubt that the
earliest of the Tertiary strata of the Majes Valley were deposited in a
time of far greater rainfall than the present. It is further concluded
that there was increasing dryness, as shown by hundreds of feet of
wind-blown sand near the top of the section. But the growing dryness was
interrupted by at least one period of greater precipitation. Since that
time there has been a return to the dry climate of a former epoch.

Uplift and erosion of the earliest of the Tertiary deposits of the Majes
Valley is indicated in two ways: (1) by the deformed character of the
beds, and (2) by the ensuing coarse deposits which were derived from the
invigorated streams. Without strong deformations it would not be
possible to assign the increased erosion so confidently to uplift; with
the coarse deposits that succeed the unconformity we have evidence of
accumulation under conditions of renewed uplift in the mountains and of
full streams competent to remove the increasing load.

It is in the character of the sediments toward the top of the Tertiary
that we have the clearest evidence of progressive desiccation of the
climate of the region. The amount of wind-blown material steadily
increases and the uppermost five hundred feet is composed predominantly,
and in places exclusively, of this material. The evidences of wind
action lie chiefly in the fine (in places fluffy) nature of the
deposits, their uniform character, and in the tangency of the layers
with respect to the surface on which they were deposited. There are
three diagnostic structural features of great importance: the very steep
dip of the fine laminae; the peculiar and harmonious blending of their
contacts; the manner in which the highly inclined laminae cut off and
succeed each other, whereby quite bewildering changes in the direction
of dip of the inclined beds are brought about on any exposed plane. Some
of these features require further discussion.

It is well known that the front of a sand dune generally consists of
sand deposited on a slope inclined at the angle of repose, say between
30° and 35°, and rolled into place up the long back slope of the dune by
the wind. It has not, however, been generally recognized that the angle
of repose may be exceeded (a) when there exists a strong back eddy or
(b) when the wind blows violently and for a short time in the opposite
direction. In either case sand is carried up the short steep slope of
the dune front and accumulated at an angle not infrequently running up
to 43° and 48° and locally, and under the most favorable circumstances,
in excess of 50°. The conditions under which these steep angles are
attained are undoubtedly not universal, but they can be found in some
parts of almost any desert in the world. They appear not to be present
where the sand grains are of uniform size throughout, since that leads
to rolling. They are found rather where there is a certain limited
variation in size that promotes packing. Packing and the development of
steep slopes are also facilitated in parts of the coastal desert of Peru
by a cloud canopy that hangs over the desert in the early morning, that
in the most favorable places moistens even the dune surfaces and that
has least penetration on the steep semi-protected dune fronts. Sand
later blown up the dune front or rolled down from the dune crest is
encouraged to remain near the cornice on an abnormally steep slope by
the attraction which the slightly moister sand has for the dry grains
blown against it. Since dunes travel and since their front layers,
formed on steep slopes, are cut off to the level of the surface in the
rear of the dune, it follows that the steepest dips in exposed sections
are almost always less than those in existing dunes. Exceptions to the
rule will be noted in filled hollows not re-excavated until deeply
covered by wind-blown material. These, re-exposed at the end of a long
period of wind accumulation, may exhibit even the maximum dips of the
dune cornices. Such will be conspicuously the case in sections in
aggraded desert deposits. On the border of the Majes Valley, from 400 to
500 feet of wind-accumulated deposits may be observed, representing a
long period of successive dune burials.

The peculiar blending of the contact lines of dune laminae, related to
the tangency commonly noted in dune accumulations, is apparently due to
the fact that the wind does not require a graded surface to work on, but
blows uphill as well as down. It is present on both the back-slope and
the front-slope deposits. Its finest expression appears to be in
districts where the dune material was accumulated by a violent wind
whose effects the less powerful winds could not destroy.

It is to the ability of the wind to transport material against, as well
as with, gravity, that we owe the third distinct quality of dune
material, the succession of flowing lines, in contrast to the succession
of now flat-lying now steeply inclined beds characteristic of
cross-bedded material deposited by water. One dune travels across the
face of the country only to be succeeded by another.[54] Even if wind
aggradation is in progress, the plain-like surface in the rear of a dune
may be excavated to the level of steeply inclined beds upon whose
truncated outcrop other inclined beds are laid, Fig. 178. The contrast
to these conditions in the case of aggradation by water is so clearly
and easily inferred that space will not be taken to point them out. It
is also true as a corollary to the above that the greater part of a body
of wind-drifted material will consist of cross-bedded layers, and not a
series of evenly divided and alternating flat-lying and cross-bedded
layers which result from deposition in active and variable currents of
water.

The caution must of course be observed that wind action and water action
may alternate in a desert region, as already described in Tarapacá in
northern Chile, so that the whole of a deposit may exhibit an
alternation of cross-bedded and flat-lying layers; but the former only
are due to wind action, the latter to water action.

Finally it may be noted that the sudden, frequent, and diversified dips
in the cross-bedding are peculiarly characteristic of wind action.
Although one sees in a given cross-section dips apparently directed only
toward the left or the right, excavation will supply a third dimension
from which the true dips may be either observed or calculated. These
show an almost infinite variety of directions of dip, even in restricted
areas, a condition due to the following causes:

(1) the curved fronts of sand dunes, which produce dips concentric with
respect to a point and ranging through 180° of arc; (2) the irregular
character of sand dunes in many places, a condition due in turn to (a)
the changeful character of the strong wind (often not the prevailing
wind) to which the formation of the dunes is due, and (b) the influence
of the local topography upon wind directions within short distances or
upon winds of different directions in which a slight change in wind
direction is followed by a large change in the local currents; (3) the
fact that all combinations are possible between the erosion levels of
the wind in successive generations of dunes blown across a given area,
hence _any_ condition at a given level in a dune may be combined with
_any other_ condition of a succeeding dune; (4) variations in the sizes
of successive dunes will lead to further contrasts not only in the
scale of the features but also in the direction and amount of the dips.

[Illustration: FIG. 178--Plan and cross-sections of superimposed sand
dunes of conventional outline. In the sections, dune _A_ is supposed to
have left only a small basal portion to be covered by dune _B_. In the
same way dune _C_ has advanced to cover both _A_ and _B_. The basal
portions that have remained are exaggerated vertically in order to
display the stratification. It is obviously not necessary that the dunes
should all be of the same size and shape and advancing in the same
direction in order to have the tangential relations here displayed. Nor
need the aggrading material be derived from true dunes. The results
would be the same in the case of sand _drifts_ with their associated
wind eddies. All bedded wind-blown deposits would have the same general
relations. No two successive deposits, no matter from what direction the
successive drifts or dunes travel, would exactly correspond in direction
and amount of dip.]

Finally, we may note that a section of dune deposits has a distinctive
feature not exhibited by water deposits. If the foreset beds of a
cross-bedded water deposit be exposed in a plane parallel to the strike
of the beds, the beds will appear to be horizontal. They could not then
be distinguished from the truly horizontal beds above and below them.
But the conditions of wind deposition we have just noted, and chiefly
the facts expressed by Fig. 178, make it impossible to select a position
in which both tangency and irregular dips are not well developed in a
wind deposit. I believe that we have in the foregoing facts and
inferences a means for the definite separation of these two classes of
deposits. Difficulties will arise only when there is a quick succession
of wind and water action in time, or where the wind produces powerful
and persistent effects without the actual formation of dunes.

The latest known deposits in the coastal region are found surmounting
the terrace tops along the coast between Camaná and Quilca, where they
form deposits several hundred feet thick in places. The age of these
deposits is determined by fossil evidence, and is of extraordinary
interest in the determination of the age of the great terraces upon
which they lie. They consist of alternating beds of coarse and fine
material, the coarser increasing in thickness and frequency toward the
bottom of the section. It is also near the bottom of the section that
fossils are now found; the higher members are locally saline and
throughout there is a marked inclination of the beds toward the present
shore. The deposits appear not to have been derived from the underlying
granite-gneiss. They are distributed most abundantly near the mouths of
the larger streams, as near the Vitor at Quilca, and the Majes at
Camaná. Elsewhere the terrace summit is swept clean of waste, except
where local clay deposits lie in the ravines, as back of Mollendo and
where “tierras blancas” have been accumulated by the wind.

These coastal deposits were laid down upon a dissected terrace up to
five miles in width. The degree of dissection is variable, and depends
upon the relation of the through-flowing streams to the Coast Range. The
Vitor and the Majes have cut down through the Coast Range, and locally
removed the terrace; smaller streams rising on the flanks of the Coast
Range either die out near the foot of the range or cross it in deep and
narrow valleys. The present drainage on the seaward slopes of the Coast
Range is entirely ineffective in reaching the sea, as was seen in 1911,
the wettest season known on the coast in years and one of the wettest
probably ever observed on this coast by man.

In consequence of their deposition on a terrace that ranges in elevation
from zero to 1,500 feet above sea level, the deposits of the coast are
very irregularly disposed. But in consequence of their great bulk they
have a rather smooth upper surface, gradation having been carried to the
point where the irregularities of the dissected terrace were smoothed
out. Their general uniformity is broken where streams cross them, or
where streams crossed them during the wetter Pleistocene. Their
elevation, several hundred feet above sea level, is responsible for the
deep dissection of their coastal margin, where great cliffs have been
cut.

PLEISTOCENE

The broad regional uplift of the Peruvian Andes in late Tertiary and in
Pleistocene times carried their summits above the level of perpetual
snow. It is still an open question whether or not uplift was
sufficiently great in the early Pleistocene to be influenced by the
first glaciations of that period. As yet, there are evidences of only
two glacial invasions, and both are considered late events on account of
the freshness of their deposits and the related topographic forms. The
coarse deposits--nearly 500 feet thick--that form the top of the desert
section described above clearly indicate a wetter climate than prevailed
during the deposition of the several hundred feet of wind-blown deposits
beneath them. But if our interpretation be correct these deposits are of
late Tertiary age, and their character and position are taken to
indicate climatic changes in the Tertiary. They may have been the mild
precursors of the greater climatic changes of glacial times. Certain it
is that they are quite unlike the mass of the Tertiary deposits. On the
other hand they are separated from the deposits of known glacial age by
a time interval of great length--an epoch in which was cut a benched
canyon nearly a mile deep and three miles wide. They must, therefore,
have been formed when the Andes were thousands of feet lower and unable
to nourish glaciers. It was only after the succeeding uplifts had raised
the mountain crests well above the frost line that the records of
oscillating climates were left in erratic deposits, troughed valleys,
cliffed cirques and pinnacled divides.

The glacial forms are chiefly at the top of the country; the glacial
deposits are chiefly in the deep valleys that were carved before the
colder climate set in. The rock waste ground up by the ice was only a
small part of that delivered to the streams in glacial times. Everywhere
the wetter climate resulted in the partial stripping of the residual
soil gathered upon the smooth mature slopes formed during the long
Tertiary cycle of erosion. This moving sheet of waste as well as the
rock fragments carried away from the glacier ends were strewn along the
valley floors, forming a deep alluvial fill. Thereby the canyon floors
were rendered habitable.

In the chapters on human geography we have already called attention to
the importance of the U-shaped valleys carved by the glaciers. Their
floors are broad and relatively smooth. Their walls restrain the live
stock. They are sheltered though lofty. But all the human benefits
conferred by ice action are insignificant beside those due to the
general shedding of waste from the cold upper surfaces to the warm
levels of the valley floors. The alluvium-filled valleys are the seats
of dense populations. In the lowest of them tropical and sub-tropical
products are raised, like sugar-cane and cotton, in a soil that once lay
on the smooth upper slopes of mountain spurs or that was ground fine on
the bed of an Alpine glacier.

[Illustration: FIG. 179--Snow fields on the summit of the Cordillera
Vilcapampa near Ollantaytambo. A huge glacier once lay in the steep
canyon in the background and descended to the notched terminal moraine
at the canyon mouth. In places the glacier was over a thousand feet
thick. From the terminal moraine an enormous alluvial fan extends
forward to the camera and to the opposite wall of the Urubamba Valley.
It is confluent with other fans of the same origin. See Fig. 180. In the
foreground are flowers, shrubs, and cacti. A few miles below Urubamba at
11,500 feet.]

[Illustration: FIG. 180--Urubamba Valley between Ollantaytambo and
Torontoy, showing (1) more moderate upper slopes and steeper lower
slopes of the two-cycle mountain spurs; (2) the extensive alluvial
deposits of the valley, consisting chiefly of confluent alluvial fans
heading in the glaciated mountains on the left. See Fig. 179.]

[Illustration: FIG. 181--Glacial features of the Central Ranges (see
Fig. 204). Huge lateral moraines built by ice streams tributary to the
main valley north of Chuquibambilla. That the tributaries persisted long
after the main valley became free of ice is shown by the descent of the
lateral moraines over the steep border of the main valley and down to
the floor of it.]

The Pleistocene deposits fall into three well-defined groups: (1)
glacial accumulations at the valley heads, (2) alluvial deposits in
the valleys, and (3) lacustrine deposits formed on the floors of
temporary lakes in inclosed basins. Among these the most variable in
form and composition are the true glacier-laid deposits at the valley
heads. The most extensive are the fluvial deposits accumulated as valley
fill throughout the entire Andean realm. Though important enough in some
respects the lacustrine deposits are of small extent and of rather local
significance. Practically none of them fall within the field of the
present expedition; hence we shall describe only the first two classes.

The most important glacial deposits were accumulated in the eastern part
of the Andes as a result of greater precipitation, a lower snowline, and
catchment basins of larger area. In the Cordillera Vilcapampa glaciers
once existed up to twelve and fifteen miles in length, and those several
miles long were numerous both here and throughout the higher portions of
the entire Cordillera, save in the belt of most intense volcanic action,
which coincides with the driest part of the Andes, where the glaciers
were either very short or wanting altogether.

Since vigorous glacial action results in general in the cleaning out of
the valley heads, no deposits of consequence occur in these locations.
Down valley, however, glacial deposits occur in the form of terminal
moraines of recession and ground moraines. The general nature of these
deposits is now so well known that detailed description seems quite
unnecessary except in the case of unusual features.

It is noteworthy that the moraines decrease in size up valley since each
valley had been largely cleaned out by ice action before the retreat of
the glacier began. Each lowermost terminal moraine is fronted by a great
mass of unsorted coarse bowldery material forming a fill in places
several hundred feet thick, as below Choquetira and in the Vilcapampa
Valley between Vilcabamba and Puquiura. This bowldery fill is quite
distinct from the long, gently inclined, and stratified valley train
below it, or the marked ridge-like moraine above it. It is in places a
good half mile in length. Its origin is believed to be due to an
overriding action beyond the last terminal moraine at a time when the
ice was well charged with débris, an overriding not marked by morainal
accumulations, chiefly because the ice did not maintain an extreme
position for a long period.

In the vicinity of the terminal moraines the alluvial valley fill is
often so coarse and so unorganized as to look like till in the cut banks
along the streams, though its alluvial origin is always shown by the
topographic form. This characteristic is of special geologic interest
since the form may be concealed through deposition or destroyed by
erosion, and no condition but the structure remain to indicate the
manner of origin of the deposit. In such an event it would not be
possible to distinguish between alluvium and till. The gravity of the
distinction appears when it is known that such apparently unsorted
alluvium may extend for several miles forward of a terminal moraine, in
the shape of a widespreading alluvial fan apparently formed under
conditions of extremely rapid aggradation. I suppose it would not be
doubted in general that a section of such stony, bowldery, unsorted
material two miles long would have other than a glacial origin, yet such
may be the case. Indeed, if, as in the Urubamba Valley, a future section
should run parallel to the valley across the heads of a great series of
fans of similar composition, topographic form, and origin, it would be
possible to see many miles of such material.

The depth of the alluvial valley fill due to tributary fan accumulation
depends upon both the amount of the material and the form of the valley.
Below Urubamba in the Urubamba Valley a fine series is displayed, as
shown in Fig. 180. The fans head in valleys extending up to snow-covered
summits upon whose flanks living glaciers are at work today. Their heads
are now crowned by terminal moraines and both moraines and alluvial fans
are in process of dissection. The height and extent of the moraines and
the alluvial fans are in rough proportion and in turn reflect the
height, elevation, and extent of the valley heads which served as fields
of nourishment for the Pleistocene glaciers. Where the fans were
deposited in narrow valleys the effect was to increase the thickness of
the deposits at the expense of their area, to dam the drainage lines or
displace them, and to so load the streams that they have not yet
cleared their beds after thousands of years of work under torrential
conditions.

Below Urubamba the alluvial fans entering the main valley from the east
have pushed the river against its western valley wall, so that the river
flows on one side against rock and on the other against a hundred feet
of stratified material. In places, as at the head of the narrows on the
valley trail to Ollantaytambo, a flood plain has been formed in front of
the scarp cut into the alluvium, while the edge of the dissected
alluvial fans has been sculptured into erosion forms resembling
bad-lands topography. On the western side of the valley the alluvial
fans are very small, since they are due to purely local accumulations of
waste from the edge of the plateau. Glaciation has here displaced the
river. Its effects will long be felt in the disproportionate erosion of
the western wall of the valley.

By far the most interesting of the deposits of glacial time are those
laid down on the valley floors in the form of an alluvial fill. Though
such deposits have greater thickness as a rule near the nourishing
moraines or bordering alluvial fans at the lower ends of the valleys,
they are everywhere important in amount, distinctive in topographic
form, and of amazingly wide extent. They reach far into and possibly
across the Amazon basin, they form a distinct though small piedmont
fringe along the eastern base of the Andes, and they are universal
throughout the Andean valleys. That a deposit of such volume--many times
greater than all the material accumulated in the form of high-level
alluvial fans or terminal moraines--should originate in a tropical land
in a region that suffered but limited Alpine glaciation vastly increases
its importance.

[Illustration: FIG. 182--Dissected alluvial fans on the border of the
Urubamba Valley near Hacienda Chinche. A Characteristic feature of the
valleys of the Peruvian Andes below the zone of glaciation but within
the limits of its aggraditional effects. Through alluviation the valleys
and basins of the Andean Cordillera, and vast areas of the great Amazon
plains east of it, felt the effects of the glacial conditions of a past
age.]

The fill is composed of both fine and coarse material laid down by water
in steep valley floors to a depth of many feet. It breaks the steep
slope of each valley, forming terraces with pronounced frontal scarps
facing the river. On the raw bluffs at the scarps made by the
encroaching stream good exposures are afforded. At Chinche in the
Urubamba Valley above Santa Ana, the material is both sand and clay with
an important amount of gravel laid down with steep valleyward
inclination and under torrential conditions; so that within a given bed
there may be an apparent absence of lamination. Almost identical
conditions are exhibited frequently along the railway to Cuzco in the
Vilcanota Valley. The material is mixed sand and gravel, here and there
running to a bowldery or stony mass where accessions have been received
from some source nearby. It is modified along its margin not only in
topographic form but also in composition by small tributary alluvial
fans, though these in general constitute but a small part of the total
mass. At Cotahuasi, Fig. 29, there is a remarkable fill at least four
hundred feet deep in many places where the river has exposed fine
sections. The depth of the fill is, however, not determined by the
height of the erosion bluffs cut into it, since the bed of the river is
made of the same material. The rock floor of the valley is probably at
least an additional hundred feet below the present level of the river.

[Illustration: FIG. 183--Two-cycle slopes and alluvial fill between
Iluichihua and Chuquibambilla. The steep slopes on the inner valley
border are in many places vertical and rock cliffs are everywhere
abundant. Mature slopes have their greatest development here between
13,500 and 15,000 feet (4,110 to 4,570 m.). Steepest mature slopes run
from 15° to 21°. Least steep are the almost level spur summits. The
depths of the valley fill must be at least 300, and may possibly be 500
feet. The break between valley fill and steep slopes is most pronounced
where the river runs along the valley wall or undercuts it; least
pronounced where alluvial fans spread out from the head of some ravine.
It is a bowldery, stony fill almost everywhere terraced and cultivated.]

Similar conditions are well displayed at Huadquiña, where a fine series
of terraces at the lower end of the Torontoy Canyon break the descent of
the environing slopes; also in the Urubamba Valley below Rosalina, and
again at the edge of the mountains at the Pongo de Mainique. It is
exhibited most impressively in the Majes Valley, where the bordering
slopes appear to be buried knee-deep in waste, and where from any
reasonable downward extension of rock walls of the valley there would
appear to be at least a half mile of it. It is doubtful and indeed
improbable that the entire fill of the Majes Valley is glacial, for
during the Pliocene or early Pleistocene there was a submergence which
gave opportunity for the partial filling of the valley with non-glacial
alluvium, upon which the glacial deposits were laid as upon a flat and
extensive floor that gives an exaggerated impression of their depth.
However, the head of the Majes Valley contains at least six hundred feet
and probably as much as eight hundred feet of alluvium now in process of
dissection, whose coarse texture and position indicates an origin under
glacial conditions. The fact argues for the great thickness of the
alluvial material of the lower valley, even granting a floor of Pliocene
or early Pleistocene sediments. The best sections are to be found just
below Chuquibamba and again about halfway between that city and Aplao,
whereas the best display of the still even-floored parts of the valley
are between Aplao and Cantas, where the braided river still deposits
coarse gravels upon its wide flood plain.

CHAPTER XVI

GLACIAL FEATURES

THE SNOWLINE

South America is classical ground in the study of tropical snowlines.
The African mountains that reach above the snowline in the equatorial
belt--Ruwenzori, Kibo, and Kenia--have only been studied recently
because they are remote from the sea and surrounded by bamboo jungle and
heavy tropical forest. On the other hand, many of the tropical mountains
of South America lie so near the west coast as to be visible from it and
have been studied for over a hundred years. From the days of Humboldt
(1800) and Boussingault (1825) down to the present, observations in the
Andes have been made by an increasing number of scientific travelers.
The result is a large body of data upon which comparative studies may
now be profitably undertaken.

Like scattered geographic observations of many other kinds, the earlier
studies on the snowline have increased in value with time, because the
snowline is a function of climatic elements that are subject to periodic
changes in intensity and cannot be understood by reference to a single
observation. Since the discovery of physical proofs of climatic changes
in short cycles, studies have been made to determine the direction and
rate of change of the snowline the world over, with some very striking
results.

It has been found[55] that the changes run in cycles of from thirty to
thirty-five years in length and that the northern and southern
hemispheres appear to be in opposite phase. For example, since 1885 the
snowline in the southern hemisphere has been decreasing in elevation in
nine out of twelve cases by the average amount of nine hundred feet.
With but a single exception, the snowline in the northern hemisphere
has been rising since 1890 with an average increase of five hundred feet
in sixteen cases. To be sure, we must recognize that the observations
upon which these conclusions rest have unequal value, due both to
personal factors and to differences in instrumental methods, but that in
spite of these tendencies toward inequality they should agree in
establishing a general rise of the snowline in the northern hemisphere
and an opposite effect in the southern is of the highest significance.

It must also be realized that snowline observations are altogether too
meager and scattered in view of the abundant opportunities for making
them, that they should be standardized, and that they must extend over a
much longer period before they attain their full value in problems in
climatic variations. Once the possible significance of snowline changes
is appreciated the number and accuracy of observations on the elevation
and local climatic relations of the snowline should rapidly increase.

In 1907 I made a number of observations on the height of the snowline in
the Bolivian and Chilean Andes between latitudes 17° and 20° south, and
in 1911 extended the work northward into the Peruvian Andes along the
seventy-third meridian. It is proposed here to assemble these
observations and, upon comparison with published data, to make a few
interpretations.

From Central Lagunas, Chile, I went northeastward via Pica and the
Huasco Basin to Llica, Bolivia, crossing the Sillilica Pass in May,
1907, at 15,750 feet (4,800 m.). Perpetual snow lay at an estimated
height of 2,000-2,500 feet above the pass or 18,000 feet (5,490 m.)
above the sea. Two weeks later the Huasco Basin, 14,050 feet (4,280 m.),
was covered a half-foot deep with snow and a continuous snow mantle
extended down to 13,000 feet. Light snows are reported from 12,000 feet,
but they remain a few hours only and are restricted to the height of
exceptionally severe winter seasons (June and early July). Three or four
distant snow-capped peaks were observed and estimates made of the
elevation of the snowline between the Cordillera Sillilica and Llica on
the eastern border of the Maritime Cordillera. All observations agreed
in giving an elevation much in excess of 17,000 feet. In general the
values run from 18,000 to 19,000 feet (5,490 to 5,790 m.). Though the
bases of these figures are estimates, it should be noted that a large
part of the trail lies between 14,000 and 16,000 feet, passing mountains
snow-free at least 2,000 to 3,000 feet higher, and that for general
comparisons they have a distinct value.

In the Eastern Cordillera of Bolivia, snow was observed on the summit of
the Tunari group of peaks northwest of Cochabamba. Steinmann, who
visited the region in 1904, but did not reach the summit of the Tunari
group of peaks, concludes that the limit of perpetual snow should be
placed above the highest point, 17,300 (5,270 m.); but in July and
August, 1907, I saw a rather extensive snow cover over at least the
upper 1,000 feet, and what appeared to be a very small glacier. Certain
it is that the Cochabamba Indians bring clear blue ice from the Tunari
to the principal hotels, just as ice is brought to Cliza from the peaks
above Arani. On these grounds I am inclined to place the snowline at
17,000 feet (5,180 m.) near the eastern border of the Eastern
Cordillera, latitude 17° S. At 13,000 feet, in July, 1907, snow occurred
in patches only on the pass called Abre de Malaga, northeast of Colomi,
13,000 feet, and fell thickly while we were descending the northern
slopes toward Corral, so that in the early morning it extended to the
cold timber line at 10,000 feet. In a few hours, however, it had
vanished from all but the higher and the shadier situations.

In the Vilcanota knot above the divide between the Titicaca and
Vilcanota hydrographic systems, the elevation of the snowline was
16,300+ feet (4,970 m.) in September, 1907. On the Cordillera Real of
Bolivia it is 17,000 to 17,500 feet on the northeast, but falls to
16,000 feet on the southwest above La Paz. In the first week of July,
1911, snow fell on the streets of Cuzco (11,000 feet) and remained for
over an hour. The heights north of San Geronimo (16,000 feet) miss the
limit of perpetual snow and are snow-covered only a few months each
year.

In taking observations on the snowline along the seventy-third meridian
I was fortunate enough to have a topographer the heights of whose
stations enabled me to correct the readings of my aneroid barometer
whenever these were taken off the line of traverse. Furthermore, the
greater height of the passes--15,000 to 17,600 feet--brought me more
frequently above the snowline than had been the case in Bolivia and
Chile. More detailed observations were made, therefore, not only upon
the elevation of the snowline from range to range, but also upon the
degree of canting of the snowline on a given range. Studies were also
made on the effect of the outline of the valleys upon the extent of the
glaciers, the influence on the position of the snowline of mass
elevation, precipitation, and cloudiness.

Snow first appears at 14,500 feet (4,320 m.) on the eastern flanks of
the Cordillera Vilcapampa, in 13° south latitude. East of this group of
ridges and peaks as far as the extreme eastern border of the mountain
belt, fifty miles distant, the elevations decrease rapidly to 10,000
feet and lower, with snow remaining on exceptionally high peaks from a
few hours to a few months. In the winter season snow falls now and then
as low as 11,500 feet, as in the valley below Vilcabamba pueblo in early
September, 1911, though it vanishes like mist with the appearance of the
sun or the warm up-valley winds from the forest. Storms gather daily
about the mountain summits and replenish the perpetual snow above 15,000
feet. In the first pass above Puquiura we encountered heavy snow banks
on the northeastern side a hundred feet below the pass (14,500 feet),
but on the southwestern or leeward side it is five hundred feet lower.
This distribution is explained by the lesser insolation on the
southwestern side, the immediate drifting of the clouds from the
windward to the leeward slopes, and to the mutual intensification of
cause and effect by topographic changes such as the extension of
collecting basins and the steeping of the slopes overlooking them with a
corresponding increase in the duration of shade.

It is well known that with increase of elevation and therefore of the
rarity of the air there is less absorption of the sun’s radiant energy,
and a corresponding increase in the degree of insolation. It follows,
therefore, that at high altitudes the contrasts between sun and shade
temperatures will increase. Frankland[56] has shown that the increase
may run as high as 500 per cent between 100 to 10,000 feet above the
sea. I have noted a fall of temperature of 15° F. in six minutes, due to
the obscuring of the sun by cloud at an elevation of 16,000 feet above
Huichihua in the Central Ranges of Peru. Since the sun shines
approximately half the time in the snow-covered portions of the
mountains and since the tropical Andes are of necessity snow-covered
only at lofty elevations, this contrast between shade and sun
temperatures is by far the most powerful factor influencing differences
in elevation of the snowline in Peru.

To the drifting of the fallen snow is commonly ascribed a large portion
of this contrast. I have yet to see any evidence of its action near the
snowline, though I have often observed it, especially under a high wind
in the early morning hours at considerable elevations above the
snowline, as at the summits of lofty peaks. It appears that the lower
ranges bearing but a limited amount of snow are not subject to drifting
because of the wetness of the snow, and the fact that it is compacted by
occasional rains and hail storms. Only the drier snow at higher
elevations and under stronger winds can be effectively dislodged.

The effect of unequal distribution of precipitation on the windward and
leeward slopes of a mountain range is in general to depress the snowline
on the windward slopes where the greater amount falls, but this may be
offset in high altitudes by temperature contrasts as in the westward
trending Cordillera Vilcapampa, where north and south slopes are in
opposition. If the Cordillera Vilcapampa ran north and south we should
have the windward and leeward slopes equally exposed to the sun and the
snowline would lie at a lower elevation on the eastern side. Among all
the ranges the slopes have decreasing precipitation to the leeward, that
is, westerly. The second and third passes, between Arma and Choquetira,
are snow-free (though their elevations equal those of the first pass)
because they are to leeward of the border range, hence receive less
precipitation. The depressive effect of increased precipitation on the
snowline is represented by A-B, Fig. 184; in an individual range the
effect of heavier precipitation may be offset by temperature contrasts
between shady and sunny slopes, as shown by the line a-b in the same
figure.

The degree of canting of the snowline on opposite slopes of the
Cordillera Vilcapampa varies between 5° and 12°, the higher value being
represented four hours southwest of Arma on the Choquetira trail,
looking northeast. A general view of the Cordillera looking east at this
point (Fig. 186), shows the appearance of the snowline as one looks
along the flanks of the range. In detail the snowline is further
complicated by topography and varying insolation, each spur having a
snow-clad and snow-free aspect as shown in the last figure. The degree
of difference on these minor slopes may even exceed the difference
between opposite aspects of the range in which they occur.

[Illustration: FIG. 184--To illustrate the canting of the snowline.
_A-B_ is the snowline depressed toward the north (right) in response to
heavier precipitation. The line _a-b_ represents a depression in the
opposite direction due to the different degree of insolation on the
northern (sunny) and southern (shady) slopes.]

To these diversifying influences must be added the effect of warm
up-valley winds that precede the regular afternoon snow squalls and that
melt the latest fall of snow to exceptionally high elevations on both
the valley floor and the spurs against which they impinge. The influence
of the warmer air current is notably confined to the heads of those
master valleys that run down the wind, as in the valley heading at the
first pass, Cordillera Vilcapampa, and at the heads of the many valleys
terminating at the passes of the Maritime Cordillera. Elsewhere the
winds are dissipated in complex systems of minor valleys and their
effect is too well distributed to be recognized.

It is clear from the conditions of the problem as outlined on preceding
pages that the amount of canting may be expressed in feet of difference
of the snowline on opposite sides of a range or in degrees. The former
method has, heretofore, been employed. It is proposed that this method
should be abolished and degrees substituted, on the following grounds:
Let _A_ and _B_, Fig. 190, represent two mountain masses of unequal area
and unequal elevation. Let the opposite ends of the snowlines of both
figures lie 1,000 feet apart as between the windward and leeward sides
of a broad cordillera (A), or as between the relatively sunnier and
relatively shadier slopes of individual mountains or narrow ranges in
high latitudes or high altitudes (B). With increasing elevation there is
increasing contrast between temperatures in sunshine and in shade, hence
a greater degree of canting (B). Tending toward a still greater degree
of contrast is the effect of the differences in the amounts of snowy
precipitation, which are always more marked on an isolated and lofty
mountain summit than upon a broad mountain mass (1) because in the
former there is a very restricted area where snow may accumulate, and
(2) because with increase of elevation there is a rapid and differential
decrease in both the rate of adiabatic cooling and the amount of water
vapor; hence the snow-producing forces are more quickly dissipated.

[Illustration: FIG. 185--Glacial features in the Peruvian Andes near
Arequipa. Sketched from a railway train, July, 1911. The horizontal
broken lines represent the lower limit of light snow during late June,
1911. There is a fine succession of moraines in U-shaped valleys in all
the mountains of the Arequipa region. _A_ represents a part of Chacchani
northwest of Arequipa; _B_ is looking south by east at the northwest end
of Chacchani near Pampa de Arrieros; _C_ also shows the northwest end of
Chacchani from a more distant point.]

[Illustration: FIG. 186--Canted snowline in the Cordillera Vilcapampa
between Arma and Choquetira. Looking east from 13,500 feet.]

[Illustration: FIG. 187--Glacial topography between Lambrama and
Antabamba in the Central Ranges. A recent fall of snow covers the
foreground. The glaciers are now almost extinct and their action is
confined to the deepening and steepening of the cirques at the valley
heads.]

[Illustration: FIG. 188--Asymmetrical peaks in the Central Ranges
between Antabamba and Lambrama. The snow-filled hollows in the
photograph face away from the sun--that is, south--and have retained
snow since the glacial epoch; while the northern slopes are snow-free.
There is no true glacial ice and the continued cirque recession is due
to nivation.]

[Illustration: FIG. 189--Glacial topography north of the divide on the
seventy-third meridian. Maritime Cordillera. Looking downstream at an
elevation of 16,500 feet (5,030 m.).]

Furthermore, the leeward side of a lofty mountain not only receives much
less snow proportionally than the leeward side of a lower mountain,
but also loses it faster on account of the smaller extent of surface
upon which it is disposed and the proportionally larger extent of
counteractive, snow-free surface about it. Among the volcanoes of
Ecuador are many that show differences of 500 feet in snowline elevation
on windward and leeward (east) slopes and some, as for example
Chimborazo, that exhibit differences of 1,000 feet. The latter figure
also expresses the differences in the broad Cordillera Vilcapampa and in
the Maritime Cordillera, though the _rate_ of canting as expressed in
degrees is much greater in the case of the western mountains.

[Illustration: FIG. 190--To illustrate the difference in the degree of
canting of the snowline on large and on small mountain masses.]

The advantages of the proposed method of indicating the degree of
canting of the snowline lie in the possibility thus afforded of
ultimately separating and expressing quantitatively the various factors
that affect the position of the line. In the Cordillera Vilcapampa, for
example, the dominant canting force is the difference between sun and
shade temperatures, while in the volcanoes of Ecuador, where
_symmetrical volcanoes, almost on the equator, have equal insolation on
all aspects_ and the temperature contrasts are reduced to a minimum--the
differences are owing chiefly to varying exposure to the winds. The
elusive factors in the comparison are related to the differences in area
and in elevation.

The value of arriving finally at close snowline analyses grows out of
(1) the possibility of snowline changes in short cycles and (2)
uncertainty of arriving by existing methods at the snowline of the
glacial period, whose importance is fundamental in refined physiographic
studies in glaciated regions with a complex topography. To show the
application of the latter point we shall now attempt to determine the
snowline of the glacial period in the belt of country along the route of
the Expedition.

In the group of peaks shown in Fig. 188 between Lambrama and Antabamba,
the elevation of the snowline varies from 16,000 to 17,000 feet
(4,880-5,180 m.), depending on the topography and the exposure. The
determination of the limit of perpetual snow was here, as elsewhere
along the seventy-third meridian, based upon evidences of nivation. It
will be observed in Fig. 191 that just under the snow banks to the left
of the center are streams of rock waste which head in the snow. Their
size is roughly proportional to the size of the snow banks, and,
furthermore, they are not found on snow-free slopes. From these facts it
is concluded that they represent the waste products of snow erosion or
nivation, just as the hollows in which the snow lies represent the
topographic products of nivation. On account of the seasonal and annual
variation in precipitation and temperature--hence in the elevation of
the snowline--it is often difficult to make a correct snowline
observation based upon depth and _apparent_ permanence. Different
observers report great changes in the snowline in short intervals,
changes not explained by instrumental variations, since they are
referred to topographic features. It appears to be impossible to rely
upon present records for small changes possibly related to minor
climatic cycles because of a lack of standardization of observations.

Nothing in the world seems simpler at first sight than an observation on
the elevation of the snowline. Yet it can be demonstrated that large
numbers of observers have merely noted the position of temporary snow.
It is strongly urged that evidences of nivation serve henceforth as
proof of permanent snow and that photographic records be kept for
comparison. In this way measurements of changes in the level of the
snowline may be accurately made and the snow cover used as a climatic
gauge.

Farther west in the Maritime Cordillera, the snowline rises to 18,000
feet on the northern slopes of the mountains and to 17,000 feet on the
southern slopes. The top of the pass above Cotahuasi, 17,600 feet (5,360
m.), was snow-free in October, 1911, but the snow extended 500 feet
lower on the southern slope. The degree of canting is extraordinary at
this point, single volcanoes only 1,500 to 2,000 feet above the general
level and with bases but a few miles in circumference exhibit a thousand
feet of difference in the snowline upon northern and southern aspects.
This is to be attributed no less to the extreme elevation of the snow
(and, therefore, stronger contrasts of shade and sun temperatures) than
to the extreme aridity of the region and the high daytime temperatures.
The aridity is a factor, since heavy snowfall means a lengthening of the
period of precipitation in which a cloud cover shuts out the sun and a
shortening of the period of insolation and melting.

Contrasts between shade and sun temperatures increase with altitude but
their effects also increase in _time_. Of two volcanoes of equal size
and both 20,000 feet above sea level, that one will show the greater
degree of canting that is longer exposed to the sun. The high daytime
temperature is a factor, since it tends to remove the thinnest snow,
which also falls in this case on the side receiving the greatest amount
of heat from the sun. The high daytime temperature is phenomenal in this
region, and is owing to the great extent of snow-free land at high
elevations and yet below the snowline, and to the general absence of
clouds and the thinness of vegetation.

On approach to the western coast the snowline descends again to 17,500
feet on Coropuna. There are three chief reasons for this condition.
First, the well-watered Majes Valley is deeply incised almost to the
foot of Coropuna, above Chuquibamba, and gives the daily strong sea
breeze easy access to the mountain. Second, the Coast Range is not only
low at the mouth of the Majes Valley, but also is cut squarely across by
the valley itself, so that heavy fogs and cloud sweep inland nightly and
at times completely cover both valley and desert for an hour after
sunrise. Although these yield no moisture to the desert or the valley
floor except such as is mechanically collected, yet they do increase the
precipitation upon the higher elevations at the valley head.

[Illustration: THE YALE PERUVIAN EXPEDITION OF 1911

HIRAM BINGHAM DIRECTOR

ANTABAMBA QUADRANGLE]

A third factor is the size of Coropuna itself. The mountain is not a
simple volcano but a composite cone with five main summits reaching well
above the snowline, the highest to an elevation of 21,703 feet (6,615
m.). It measures about 20 miles (32 km.) in circumference at the
snowline and 45 miles (72 km.) at its base (measuring at the foot of the
steeper portion), and stands upon a great tributary lava plateau from
15,000 to 17,000 feet above sea level. Compared with El Misti, at
Arequipa, its volume is three times as great, its height two thousand
feet more, and its access to ocean winds at least thirty per cent more
favorable. El Misti, 19,200 feet (5,855 m.) has snow down as far as
16,000 feet in the wet season and rarely to 14,000 feet, though by
sunset a fall of snow may almost disappear whose lower limit at sunrise
was 16,000 feet. Snow may accumulate several thousand feet below the
summit during the wet season, and in such quantities as to require
almost the whole of the ensuing dry season (March to December) for its
melting. Northward of El Misti is the massive and extended range,
Chachani, 20,000 feet (6,100 m.) high; on the opposite side is the
shorter range called Pichu-Pichu. Snow lies throughout the year on both
these ranges, but in exceptional seasons it nearly disappears from
Chachani and wholly disappears from Pichu-Pichu, so that the snowline
then rises to 20,000 feet. It is considered that the mean of a series of
years would give a value between 17,000 and 18,000 feet for the snowline
on all the great mountains of the Arequipa region.[57] This would,
however, include what is known to be temporary snow; the limit of
“perpetual” snow, or the true snowline, appears to lie about 19,000 feet
on Chachani and _above_ El Misti, say 19,500 feet. It is also above the
crest of Pichu-Pichu. The snowline, therefore, appears to rise a
thousand feet from Coropuna to El Misti, owing chiefly to the poorer
exposure of the latter to the sources of snowy precipitation.

It may also be noted that the effect of the easy access of the ocean
winds in the Coropuna region is also seen in the increasing amount of
vegetation which appears in the most favorable situations. Thus, along
the Salamanca trail only a few miles from the base of Coropuna are a few
square kilometers of _quenigo_ woodland generally found in the cloud
belt at high altitudes; for example, at 14,000 feet above Lambrama and
at 9,000 feet on the slope below Incahuasi, east of Pasaje. The greater
part of the growth is disposed over hill slopes and on low ridges and
valley walls. It is, therefore, clearly unrelated as a whole to the
greater amount of ground-water with which a part is associated, as along
the valley floors of the streams that head in the belt of perpetual
snow. The appearance of this growth is striking after days of travel
over the barren, clinkery lava plateau to eastward that has a less
favorable exposure. The _quenigo_ forest, so-called, is of the greatest
economic value in a land so desolate as the vast arid and semi-arid
mountain of western Peru. Every passing traveler lays in a stock of
fire-wood as he rests his beasts at noonday; and long journeys are made
to these curious woodlands from both Salamanca and Chuquibamba to gather
fuel for the people of the towns.

NIVATION

The process of nivation, or snow erosion, does not always produce
visible effects. It may be so feeble as to make no impression upon very
resistant rock where the snow-fall is light and the declivity low.
Ablation may in such a case account for almost the whole of the snow
removed. On strong and topographically varied slopes where the snow is
concentrated in headwater alcoves, there is a more pronounced downward
movement of the snow masses with more prominent effects both of erosion
beneath the snow and of accumulation at the border of the snow. In such
cases the limit of perpetual snow may be almost as definitely known as
the limit of a glacier. Like glaciers these more powerful snow masses
change their limits in response to regional changes in precipitation,
temperature, or both. It would at first sight appear impossible to
distinguish between these changes through the results of nivation. Yet
in at least a few cases it may be as readily determined as the past
limits of glaciers are inferred from the terminal moraines, still
intact, that cross the valley floors far below the present limits of the
ice.

In discussing the process of nivation it is necessary to assume a
sliding movement on the part of the snow, though it is a condition in
Matthes’ original problem in which the nivation idea was introduced that
the snow masses remain stationary. It is believed, however, that
Matthes’ valuable observations and conclusions really involve but half
the problem of nivation; or at the most but one of two phases of it. He
has adequately shown the manner in which that phase of nivation is
expressed which we find _at the border of the snow_. Of the action
_beneath_ the snow he says merely: “Owing to the frequent oscillations
of the edge and the successive exposure of the different parts of the
site to frost action, the area thus affected will have no well-defined
boundaries. The more accentuated slopes will pass insensibly into the
flatter ones, and the general tendency will be to give the drift site a
cross section of smoothly curved outline and ordinarily concave.”[58]

From observations on the effects of nivation in valleys, Matthes further
concludes that “on a grade of about 12 per cent ... névé must attain a
thickness of at least 125 feet in order that it may have motion,”[59]
though as a result of the different line of observations Hobbs
concludes[60] that a somewhat greater thickness is required.

[Illustration: FIG. 191--The “pocked” surface characteristically
developed in the zone of light nivation. Compare with Fig. 194, showing
the effects of heavy nivation.]

[Illustration: FIG. 192--Steep cirque walls and valleys head in the
Central Ranges between Lambrama and Chuquibambilla. The snow is here a
vigorous agent in transporting talus material and soil from all the
upper slopes down to the foot of the cirque wall.]

The snow cover in tropical mountains offers a number of solid advantages
in this connection. Its limits, especially on the Cordillera Vilcapampa,
on the eastern border of the Andes, are subject to _small seasonal
oscillations_ and the edge of the “perpetual” snow is easily determined.
Furthermore, it is known from the comparatively “fixed quality of
tropical climate,” as Humboldt put it, that the variations of the
snowline in a period of years do not exceed rather narrow limits. In
mid-latitudes on the contrary there is an extraordinary shifting of the
margin of the snow cover, and a correspondingly wide distribution of
the feeble effects of nivation.

[Illustration: FIG. 193--Panta Mountain and its glacier system. The
talus-covered mass in the center (B) is a terminal moraine topped by the
dirt-stained glacier that descends from the crest. The separate glaciers
were formerly united to form a huge ice tongue that truncated the
lateral spurs and flattened the valley floor. One of its former stages
is shown by the terminal moraine in the middle distance, breached by a
stream, and impounding a lake not visible from this point of view.]

[Illustration: FIG. 194--Recessed southern slopes of volcanoes whose
northern slopes are practically without glacial modifications. Summit of
the lava plateau, Maritime Cordillera, western Peru, between Antabamba
and Cotahuasi.]

Test cases are presented in Figs. 191, 192, and 193, Cordillera
Vilcapampa, for the determination of the fact of the movement of the
snow long before it has reached the thickness Matthes or Hobbs believes
necessary for a movement of translation to begin. Fig. 191 shows snow
masses occupying pockets on the slope of a ridge that was never covered
with ice. Past glacial action with its complicating effects is,
therefore, excluded and we have to deal with snow action pure and
simple. The pre-glacial surface with smoothly contoured slopes is
recessed in a noteworthy way from the ridge crest to the snowline of the
glacial period at least a thousand feet lower. The recesses of the
figure are peculiar in that not even the largest of them involve the
entire surface from top to bottom; they are of small size and are
scattered over the entire slope. This is believed to be due to the fact
that they represent the limits of variations of the snowline in short
cycles. Below them as far as the snowline of the glacial period are
larger recesses, some of which are terminated by masses of waste as
extensive as the neighboring moraines, but disposed in irregular
scallops along the borders of the ridges or mountain slopes in which the
recesses have been found.

The material accumulated at the lower limit of the snow cover of the
glacial period was derived from two sources: (1) from slopes and cliffs
overlooking the snow, (2) from beneath the snow by a process akin to ice
plucking and abrasion. The first process is well known and resembles the
shedding of waste upon a valley glacier or a névé field from the
bordering cliffs and slopes. Material derived in this manner in many
places rolls down a long incline of snow and comes to rest at the foot
of it as a fringe of talus. The snow is in this case but a substitute
for a normal mass of talus. The second process produces its most clearly
recognizable effects on slopes exceeding a declivity of 20°; and upon
30° and 40° slopes its action is as well-defined as true glacial action
which it imitates. It appears to operate in its simplest form as if
independent of the mass of the snow, small and large snow patches
showing essentially the same results. This is the reverse of Matthes’
conclusion, since he says that though the minimum thickness “must vary
inversely with the percentage of the grade,” “the influence of the grade
is inconsiderable,” and that the law of variation must depend upon
additional observation.[61]

Let us examine a number of details and the argument based upon them and
see if it is not possible to frame a satisfactory law of variation.

In Fig. 193 the chief conditions of the problem are set forth. Forward
from the right-hand peak are snow masses descending to the head of a
talus (_A_) whose outlines are clearly defined by freshly fallen snow.
At (_B_) is a glacier whose tributaries descend the middle and left
slopes of the picture after making a descent from slopes several
thousand feet higher and not visible in this view. The line beneath the
glacier marks the top of the moraine it has built up. Moraines farther
down valley show a former greater extent of the glacier. Clearly the
talus material at (_A_) was accumulated after the ice had retreated to
its present position. It will be readily seen from an inspection of the
photograph that the total amount of material at (_A_) is an appreciable
fraction of that in the moraine. The ratio appears to be about 1:8 or
1:10. I have estimated that the total area of snow-free surface about
the snowfields of the one is to that of the other as 2:3. The gradients
are roughly equivalent, but the volume of snow in the one case is but a
small fraction of that in the other. It will be seen that the snow
masses have recessed the mountain slopes at _A_ and formed deep hollows
and that the hollowing action appears to be most effective where the
snow is thickest.

Summarizing, we note first, that the roughly equivalent factors are
gradient and amount of snow-free surface; second, that the unequal
factors are (a) accumulated waste, (b) degree of recessing, and (c) the
degree of compacting of snow into ice and a corresponding difference in
the character of the glacial agent, and (d) the extent of the snow
cover. The direct and important relation of the first two unequal
factors to the third scarcely need be pointed out.

We have then an inequality in amount of accumulated material to be
explained by either an inequality in the extent of the snow and
therefore an inequality of snow action, or an inequality due to the
presence of ice in one valley and not in the other, or by both. It is at
once clear that if ice is absent above (_A_) and the mountain slopes are
recessed that snow action is responsible for it. It is also recognized
that whatever rate of denudation be assigned to the snow-free surfaces
this rate must be exceeded by the rate of snow action, else the
inequalities of slope would be decreased rather than increased. The
accumulated material at (_A_) is, therefore, partly but not chiefly due
to denudation of snow-free surfaces. It is due chiefly to _erosion_
beneath the snow. Nor can it be argued that the hollows now occupied by
snow were formed at some past time when ice not snow lay in them. They
are not ice-made hollows for they are on a steep spur above the limits
of ice action even in the glacial period. Any past action is, therefore,
represented here in _kind_ by present action, though there would be
differences in _degree_ because the heavier snows of the past were
displaced by the lighter snows of today.

While it appears that the case presents clear proof of degradation by
snow it is not so clear how these results were accomplished. Real
abrasion on a large scale as in bowlder-shod glaciers is ruled out,
since glacial striæ are wholly absent from nivated surfaces according to
both Matthes’ observations and my own. Yet all nivated surfaces have
very distinctive qualities, delicately organized slopes which show a
marked change from any original condition related to water-carving. In
the absence of striæ, the general absence of all but a thin coating of
waste _even in rock hollows_, and the accumulation of waste up to
bowlders in size at the lower edge of the nivated zone, I conclude that
compacted snow or névé of sufficient thickness and gradient may actually
pluck rock outcrops in the same manner though not at the rate which ice
exhibits. That the products of nivation may be bowlders as well as fine
mud would seem clearly to follow increase in effectiveness, due to
increase in amount of the accumulated snow; that bowlders are actually
transported by snow is also shown by their presence on the lower margins
of nivated tracts.

Our argument may be made clearer by reference to the observed action of
snow in a particular valley. Snow is shed from the higher, steeper
slopes to the lower slopes and eventually accumulates to a marked degree
on the bottoms of the depressions, whence it is avalanched down valley
over a series of irregular steps on the valley floor. An avalanche takes
place through the breaking of a section of snow just as an iceberg
breaks off the end of a tide-water glacier. Evidently there must be
pressure from behind which crowds the snow forward and precipitates it
to a lower level.

As a snow mass falls it not only becomes more consolidated, beginning at
the plane of impact, but also gives a shock to the mass upon which it
falls that either starts it in motion or accelerates its rate of motion.
The action must therefore be accompanied by a drag upon the floor and if
the rock be close-jointed and the blocks, defined by the joint planes,
small enough, they will be transported. Since snow is not so compact as
ice and permits included blocks easily to adjust themselves to new
resistances, we should expect the detached blocks included in the snow
to change their position constantly and to form irregular scratches, but
not parallel striæ of the sort confidently attributed to stone-shod ice.

It is to the plasticity of snow that we may look for an explanation of
the smooth-contoured appearance of the landscape in the foreground of
Fig. 135. The smoothly curved lines are best developed where the entire
surface was covered with snow, as in mid-elevations in the larger
snowfields. At higher elevations, where the relief is sharper, the snow
is shed from the steeper declivities and collected in the minor basins
and valley heads, where its action tends to smooth a floor of limited
area, while snow-free surfaces retain all their original irregularities
of form or are actually sharpened.

The degree of effectiveness of snow and névé action may be estimated
from the reversed slopes now marked by ponds or small marshy tracts
scattered throughout the former névé fields, and the many niched
hollows. They are developed above Pampaconas in an admirable manner,
though their most perfect and general development is in the summit belt
of the Cordillera Vilcapampa between Arma and Choquetira, Fig. 135. It
is notable in _all_ cases where nivation was associated with the work of
valley glaciers that the rounded nivated slopes break rather sharply
with the steep slopes that define an inner valley, whose form takes on
the flat floor and under-cut marginal walls normal to valley glaciation.

A classification of numerous observations in the Cordillera Vilcapampa
and in the Maritime Cordillera between Lambrama and Antabamba may now be
presented as the basis for a tentative expression of the law of
variation respecting snow motion. The statement of the law should be
prefaced by the remark that thorough checking is required under a wider
range of conditions before we accept the law as final. Near the lower
border of the snow where rain and hail and alternate freezing and
thawing take place, the snow is compacted even though but fifteen to
twenty feet thick, and appears to have a down-grade movement and to
exercise a slight drag upon its floor when the gradient does not fall
below 20°. Distinct evidences of nivation were observed on slopes with a
declivity of 5° near summit areas of past glacial action, where the snow
did not have an opportunity to be alternately frozen and thawed.

The _thickness_ of the former snow cover could, however, not be
accurately determined, but was estimated from the topographic
surroundings to have been at least several hundred feet. Upon a 40°
slope a snow mass 50 feet thick was observed to be breaking off at a
cliff-face along the entire cross-section as if impelled forward by
thrust, and to be carrying a small amount of waste--enough distinctly to
discolor the lowermost layers--which was shed upon the snowy masses
below. With increase in the degree of compactness of the snow at
successively lower elevations along a line of snow discharge, gradients
down to 25° were still observed to carry strongly crevassed, waste-laden
snow down to the melting border. It appeared from the clear evidences of
vigorous action--the accumulation of waste, the strong crevassing, the
stream-like character of the discharging snow, and the pronounced
topographic depression in which it lay--that much flatter gradients
would serve, possibly not more than 15°, for a snow mass 150 feet wide,
30 to 40 feet thick, and serving as the outlet for a set of tributary
slopes about a square mile in area and with declivities ranging from
small precipices to slopes of 30°.

We may say, therefore, that the factors affecting the rate of motion are
(1) thickness, (2) degree of compactness, (3) diurnal temperature
changes, and (4) gradient. Among these, diurnal temperature changes
operate indirectly by making the snow more compact and also by inducing
motion directly. At higher elevations above the snowline, temperature
changes play a decreasingly important part. The thickness required
varies inversely as the gradient, and upon a 20° slope is 20 feet for
wet and compact snow subjected to alternate freezing and thawing. For
dry snow masses above the zone of effective diurnal temperature changes,
an increasing gradient is required. With a gradient of 40°, less than 50
feet of snow will move _en masse_ if moderately compacted under its own
weight; if further compacted by impact of falling masses from above, the
required thickness may diminish to 40 feet and the required declivity to
15°. The gradient may decrease to 0° or actually be reversed and motion
still continue provided the compacting snow approach true névé or even
glacier ice as a limit.

From the sharp topographic break between the truly glaciated portions of
the valley in regions subjected to temporary glaciation, it is concluded
that the eroding power of the moving mass is suddenly increased at the
point where névé is finally transformed into true ice. This
transformation must be assumed to take place suddenly to account for so
sudden a change of function as the topographic break requires. Below the
point at which the transformation occurs the motion takes place under a
new set of conditions whose laws have already been formulated by
students of glaciology.

[Illustration: FIG. 195--Curve of snow motion. Based on many
observations of snow motion to show minimum thickness of snow required
to move on a given gradient. Figures on the left represent thickness of
snow in feet. The degrees represent the gradient of the surface. The
gradients have been run in sequence down to 0° for the sake of
completing the accompanying discussion. Obviously no glacially
unmodified valley in a region of mountainous relief would start with so
low a gradient, though glacial action would soon bring it into
existence. Between +5° and -5° the curve is based on the gradients of
nivated surfaces.]

The foregoing readings of gradient and depth of snow are typical of a
large number which were made in the Peruvian Andes and which have served
as the basis of Fig. 195. It will be observed that between 15° and 20°
there is a marked change of function and again between +5° and -5°
declivity, giving a double reversed curve. The meaning of the change
between 15° and 20° is inferred to be that, with gradients over 20°,
snow cannot wholly resist gravity in the presence of diurnal temperature
changes across the freezing point and occasional snow or hail storms.
With increase of thickness compacting appears to progress so rapidly as
to permit the transfer of thrust for short distances before absorption
of thrust takes place in the displaced snow. At 250 feet thorough
compacting appears to take place, enabling the snow to move out under
its own weight on even the faintest slopes; while, with a thickness
still greater, the resulting névé may actually be forced up slight
inclines whose declivity appears to approach 5° as a limit. I have
nowhere been able to find in truly nivated areas reversed curves
exceeding 5°, though it should be added that depressions whose leeward
slopes were reversed to 2° and 3° are fairly common. If the curve were
continued we should undoubtedly find it again turning to the left at the
point where the thickness of the snow results in the transformation of
snow to ice. From the sharp topographic break observed to occur in a
narrow belt between the névé and the ice, it is inferred that the
erosive power of the névé is to that of the ice as 2:4 or 1:5 _for equal
areas_; and that reversed slopes of a declivity of 10° to 15° may be
formed by glaciers is well known. Precisely what thickness of snow or
névé is necessary and what physical conditions effect its transformation
into ice are problems not included in the main theme of this chapter.

It is important that the proposed curve of snow motion under minimum
conditions be tested under a large variety of circumstances. It may
possibly be found that each climatic region requires its special
modifications. In tropical mountains the sudden alternations of freezing
and thawing may effect such a high degree of compactness in the snow
that lower minimum gradients are required than in the case of
mid-latitude mountains where the perpetual snow of the high and cold
situations is compacted through its own weight. Observations of the
character introduced here are still unattainable, however. It is hoped
that they will rapidly increase as their significance becomes apparent;
and that they have high significance the striking nature of the curve of
motion seems clearly to establish.

BERGSCHRUNDS AND CIRQUES

The facts brought out by the curve of snow-motion (Fig. 195) have an
immediate bearing on the development of cirques, whose precise mode of
origin and development have long been in doubt. Without reviewing the
arguments upon which the various hypotheses rest, we shall begin at once
with the strongest explanation--W. D. Johnson’s famous bergschrund
hypothesis. The critical condition of this hypothesis is the diurnal
migration across the freezing point of the air temperature at the bottom
of the schrund. Alternate freezing and thawing of the water in the
joints of the rock to which the schrund leads, exercise a quarrying
effect upon the rock and, since this effect is assumed to take place at
the foot of the cirque, the result is a steady retreat of the steep
cirque wall through basal sapping.

While Johnson’s hypothesis has gained wide acceptance and is by many
regarded as the final solution of the cirque problem it has several
weaknesses in its present form. In fact, I believe it is but one of two
factors of equal importance. In the first place, as A. C. Andrews[62]
has pointed out, it is extremely improbable that the bergschrund of
glacial times under the conditions of a greater volume of snow could
have penetrated to bedrock at the base of the cirque where the present
change of slope takes place. In the second place, the assumption is
untenable that the bergschrund in all cases reaches to or anywhere near
the foot of the cirque wall. A third condition outside the hypothesis
and contradictory to it is the absence of a bergschrund in snowfields at
many valleys heads where cirques are well developed!

Johnson himself called attention to the slender basis of observation
upon which his conclusions rest. In spite of his own caution with
respect to the use of his meager data, his hypothesis has been applied
in an entirely too confident manner to all kinds of cirques under all
kinds of conditions. Though Johnson descended an open bergschrund to a
rock floor upon which ice rested, his observations raise a number of
proper questions as to the application of these valuable data: How long
are bergschrunds open? How often are they open? Do they everywhere open
to the foot of the cirque wall? Are they present for even a part of the
year in all well-developed cirques? Let us suppose that it is possible
to find many cirques filled with snow, not ice, surrounded by truly
precipitous walls and with an absence of bergschrunds, how shall we
explain the topographic depressions excavated underneath the snow? If
cirque formation can be shown to take place without concentrated frost
action at the foot of the bergschrund, then is the bergschrund not a
secondary rather than a primary factor? And must we not further conclude
that when present it but hastens an action which is common to all
snow-covered recesses?

It is a pleasure to say that we may soon have a restatement of the
cirque problem from the father of the bergschrund idea. The argument in
this chapter was presented orally to him after he had remarked that he
was glad to know that some one was finding fault with his hypothesis.
“For,” he said, with admirable spirit, “I am about to make a most
violent attack upon the so-called Johnson hypothesis.” I wish to say
frankly that while he regards the following argument as a valid addition
to the problem, he does not think that it solves the problem. There are
many of us who will read his new explanation with the deepest interest.

[Illustration: FIG. 196--Relation of cirque wall to trough’s end at the
head of a glaciated valley. The ratio of the inner to the outer radius
is 1:4.]

[Illustration: FIG. 197--Mode of cirque formation. Taking the facts of
snow depth represented in the curve, Fig. 195, and transposing them over
a profile (the heavy line) which ranges from 0° declivity to 50°, we
find that the greatest excess of snow occurs roughly in the center. Here
ice will first form at the bottom of the snow in the advancing hemicycle
of glaciation, and here it will linger longest in the hemicycle of
retreat. Here also there will be the greatest mass of névé. All of these
factors are self-stimulating and will increase in time until the floor
of the cirque is flattened or depressed sufficiently to offset through
uphill ice-flow the augmented forces of erosion. The effects of
self-stimulation are shown by “snow increase”; the ice shoe at the
bottom of the cirque is expressed by “ice factor.” The form accompanying
both these terms is merely suggestive. The top of “excess snow” has a
gradient characteristic of the surface of snow fields. A preglacial
gradient of 0° is not permissible, but I have introduced it to complete
the discussion in the text and to illustrate the flat floor of a cirque.
A bergschrund is not required for any stage of this process, though the
process is hastened wherever bergschrunds exist.]

We shall begin with the familiar fact that many valleys, now without
perpetual snow, formerly contained glaciers from 500 to 1,000 feet thick
and that their snowfields were of wide extent and great depth. At the
head of a given valley where the snow is crowded into a small
cross-section it is compacted and suffers a reduction in its volume. At
first nine times the volume of ice, the gradually compacting névé
approaches the volume of ice as a limit. At the foot of the cirque wall
we may fairly assume in the absence of direct observations, a volume
reduction of one-half due to compacting. But this is offset in the case
of a well-developed cirque by volume increases due to the convergence of
the snow from the surrounding slopes, as shown in Fig. 196. Taking a
typical cirque from a point above Vilcabamba pueblo I find that the
radius of the trough’s end is to the radius of the upper wall of the
cirque as 1:4; and since the corresponding surfaces are to one another
as the squares of their similar dimensions we have 1:4 or 1:16 as the
ratio of their snow areas. If no compacting took place, then to
accommodate all the snow in the glacial trough would require an increase
in thickness in the ratio of 1:4. If the snow were compacted to half its
original volume then the ratio would be 1:2. Now, since the volume ratio
of ice to snow is 1:9 and the thickness of the ice down valley is, say
400 feet, the equivalent of loose snow at the foot of the cirque must be
more than 1:4 over 1:9 or more than two and one-quarter times thicker,
or 400 feet thick; and would give a pressure of (900 ÷ 10) × 62.5
pounds, or 5,625 pounds, or a little less than three tons per square
foot. Since a pressure of 2,500 pounds per square foot will convert snow
into ice at freezing temperature, it is clear that ice and not snow was
the state at the bottom of the mass in glacial times. Further, between
the surface of the snow and the surface of the bottom layer of the ice
there must have been every gradation between loose snow and firm ice,
with the result that a thickness much less than 900 feet must be
assumed. Precisely what thickness would be found at the foot of the
cirque wall is unknown. But granting a thickness of 400 feet of ice an
additional 300 feet for névé and snow would raise the total to 700 feet.

The application of the facts in the above paragraph is clearly seen when
we refer to Fig. 197. The curve of snow motion of Fig. 195 is applied to
an unglaciated mountain valley. Taking a normal snow surface and filling
the valley head it is seen that the excess of snow depth over the amount
required to give motion is a measure at various points in the valley
head and at different gradients of the erosive force of the snow. It is
strikingly concentrated on the 15°-20° gradient which is precisely where
the so-called process of basal sapping is most marked. If long continued
the process will lead to the developing of a typical cirque for it is a
process that is self-stimulating. The more the valley is changed in form
the more it tends to change still further in form because of deepening
snowfields until cliffed pinnacles and matterhorns result.

By further reference to the figure it is clear that a schrund 350 feet
deep could not exist on a cirque wall with a declivity of even 20°
without being closed by flow, unless we grant _more rapid flow_ below
the crevasse. In the case of a glacier flowing over a nearly flat bed
away from the cirque it is difficult to conceive of a rate of flow
greater than that of snow and névé on the steep lower portion of the
cirque wall, when movement on that gradient _begins_ with snow but 20
feet thick.

In contrast to this is the view that the schrund line should lie well up
the cirque wall where the snow is comparatively thin and where there is
an approach to the lower limits of movement. The schrund would appear to
open where the bottom material changes its form, i.e., where it first
has its motion accelerated by transformation into névé. In this view
the schrund opens not at the foot of the cirque wall but well above it
as in Fig. 198, in which _C_ represents snow from top to bottom; _B_,
névé; and _A_, ice. The required conditions are then (1) that the
steepening of the cirque wall from _x_ to _y_ should be effected by
sapping originated at _y_ through the agencies outlined by Johnson; (2)
that the steepening from _x_ to _y_ should be effected by sapping
originated at _x_ through the change of the agent from névé to ice with
a sudden change of function; (3) and that the essential unity of the
wall _x-y-z_ be maintained through the erosive power of the névé, which
would tend to offset the formation of a shelf along a horizontal plane
passed through _y_. The last-named process not only appears entirely
reasonable from the conditions of gradient and depth outlined on pp. 296
to 298, but also meets the actual field conditions in all the cases
examined in the Peruvian Andes. This brings up the second and third of
our main considerations, that the bergschrund does not always or even in
many cases reach the foot of the cirque wall, and that cirques exist in
many cases where bergschrunds are totally absent.

It is a striking fact that frost action at the bottom of the bergschrund
has been assumed to be the only effective sapping force, in spite of the
common observation that bergschrunds lie in general well toward the
upper limits of snowfields--so far, in fact, that their bottoms in
general occur several hundred feet above the cirque floors. Is the
cirque under these circumstances a result of the schrund or is the
schrund a result of the cirque? _In what class of cirques do schrunds
develop?_ If cirque development in its early stages is not marked by the
development of bergschrunds, then are bergschrunds an _essential_
feature of cirques in their later stages, however much the sapping
process may be hastened by schrund formation?

Our questions are answered at once by the indisputable facts that many
schrunds occur well toward the upper limit of snow, and that many
cirques exist whose snowfields are not at all broken by schrunds. It was
with great surprise that I first noted the bergschrunds of the Central
Andes, especially after becoming familiar with Johnson’s apparently
complete proof of their genetic relation to the cirques. But it was less
surprising to discover the position of the few observed--high up on the
cirque walls and always near the upper limit of the snowfields.

A third fact from regions once glaciated but now snow-free also combined
with the two preceding facts in weakening the wholesale application of
Johnson’s hypothesis. In many headwater basins the cirque whose wall at
a distance seemed a unit was really broken into two unequal portions; a
lower, much grooved and rounded portion and an upper unglaciated,
steep-walled portion. This condition was most puzzling in view of the
accepted explanation of cirque formation, and it was not until the two
first-named facts and the applications of the curves of snow motion were
noted that the meaning of the break on the cirque became clear.
Referring to Fig. 198 we see at once that the break occurs at _y_ and
means that under favorable topographic and geologic conditions sapping
at _y_ takes place faster than at _x_ and that the retreat of _y-z_ is
faster than _x-y_. It will be clear that when these conditions are
reversed or sapping at _x_ and at _y_ are equal a single wall will
result. On reference to the literature I find that Gilbert recently
noted this feature and called it the _schrundline_.[63] He believes that
it marks the base of the bergschrund _at a late stage in the excavation
of the cirque basin_. He notes further that the lower less-steep slope
is glacially scoured and that it forms “a sort of shoulder or terrace.”

[Illustration: FIG. 198--The development of cirques. See text, p. 209,
and Fig. 199.]

If all the structural and topographic conditions were known in a great
variety of gathering basins we should undoubtedly find in them, and not
in special forms of ice erosion, an explanation of the various forms
assumed by cirques. The limitations inherent in a high-altitude field
and a limited snow cover prevented me from solving the problem, but it
offered sufficient evidence at least to indicate the probable lines of
approach to a solution. For example it is noteworthy that in _all_ the
cases examined the schrundline was better developed the further glacial
erosion had advanced. So constantly did this generalization check up,
that if at a distance a short valley was observed to end in a cirque, I
knew at once and long before I came to the valley head that a shoulder
below the schrundline did not exist. At the time this observation was
made its significance was a mystery, but it represents a condition so
constant that it forms one of the striking features of the glacial forms
in the headwater region.

[Illustration: FIG. 199--Further stages in the development of cirques.
See p. 299 and Fig. 198.]

The meaning of this feature is represented in Fig. 199, in which three
successive stages in cirque development are shown. In _A_, as displayed
in small valleys or mountainside alcoves which were but temporarily
occupied by snow and ice, or as in all higher valleys during the earlier
stages of the advancing hemicycle of glaciation, snow collects, a short
glacier forms, and a bergschrund develops. As a result of the
concentrated frost action at the base of the bergschrund a rapid
deepening and steepening takes place at _a_. As long as the depth of
snow (or snow and névé) is slight the bergschrund may remain open. But
its existence at this particular point is endangered as the cirque
grows, since the increasing steepness of the slope results in more rapid
snow movement. Greater depth of snow goes hand in hand with increasing
steepness and thus favors the formation of névé and even ice at the
bottom of the moving mass and a constantly accelerated rate of motion.
At the same time the bergschrund should appear higher up for an
independent reason, namely, that it tends to form between a mass of
slight movement and one of greater movement, which change of function,
as already pointed out, would appear to be controlled by change from
snow to névé or ice on the part of the bottom material.

The first stages in the upward migration of the bergschrund will not
effect a marked change from the original profile, since the converging
slopes, the great thickness of névé and ice at this point, and the steep
gradient all favor powerful erosion. When, however, stage _C_ is
reached, and the bergschrund has retreated to _c″_, a broader terrace
results below the schrundline, the gradient is decreased, the ice and
névé (since they represent a constant discharge) are spread over a
greater area, hence are thinner, and we have the cirque taking on a
compound character with a lower, less steep and an upper, precipitous
section.

It is clear that a closely jointed and fragile rock might be quarried by
moving ice at _c′-c″_ and the cirque wall extended unbroken to _x_; it
is equally clear that a homogeneous, unjointed granite would offer no
opportunities for glacial plucking and would powerfully resist the much
slower process of abrasion. Thus Gilbert[64] observed the schrundline in
the granites of the Sierra Nevada, which are “in large part
structureless” and my own observations show the schrundline well
developed in the open-jointed granites of the Cordillera Vilcapampa and
wholly absent in the volcanoes of the Maritime Cordillera, where ashes
and cinders, the late products of volcanic action, form the easily
eroded walls of the steep cones. Somewhere between these extremes--lack
of a variety of observations prevents our saying where--the resistance
and the internal structure of the rock will just permit a cirque wall to
extend from _x_ to _c′ ″_ of Fig. 199.

A common feature of cirques that finds an explanation in the proposed
hypothesis is the notch that commonly occurs at some point where a
convergence of slopes above the main cirque wall concentrates snow
discharge. It is proposed to call this type the notched cirque. It is
highly significant that these notches are commonly marked by even
steeper descents at the point of discharge into the main cirque than the
remaining portion of the cirque wall, even when the discharge was from a
very small basin and in the form of snow or at the most névé. The excess
of discharge at a point on the basin rim ought to produce the form we
find there under the conditions of snow motion outlined in earlier
paragraphs. It is also noteworthy that it is at such a point of
concentrated discharge that crevasses no sooner open than they are
closed by the advancing snow masses. To my mind the whole action is
eminently representative of the action taking place elsewhere along the
cirque wall on a smaller scale.

What seems a good test of the explanation of cirques here proposed was
made in those localities in the Maritime Cordillera, where large
snowbanks but not glaciers affect the form of the catchment basins. A
typical case is shown in Fig. 201. As in many other cases we have here a
great lava plateau broken frequently by volcanic cones of variable
composition. Some are of lava, others consist of ashes, still others of
tuff and lava and ashes. At lower elevations on the east, as at 16,000
feet between Antabamba and Huancarama, evidences of long and powerful
glaciers are both numerous and convincing. But as we rise still higher
the glaciated topography is buried progressively deeper under the
varying products of volcanic action, until finally at the summit of the
lava fields all evidences of glaciation disappear in the greater part of
the country between Huancarama and the main divide. Nevertheless, the
summit forms are in many cases as significantly altered as if they had
been molded by ice. Precipitous cirque walls surround a snow-filled
amphitheater, and the process of deepening goes forward under one’s
eyes. No moraines block the basin outlets, no U-shaped valleys lead
forward from them. We have here to do with post-glacial action pure and
simple, the volcanoes having been formed since the close of the
Pleistocene.

Likewise in the pass on the main divide, the perpetual snow has begun
the recessing of the very recent volcanoes bordering the pass. The
products of snow action, muds and sands up to very coarse gravel,
glaciated in texture with an intermingling of blocks up to six inches in
diameter in the steeper places, are collected into considerable masses
at the snowline, where they form broad sheets of waste so boggy as to be
impassable except by carefully selected routes. No ice action whatever
is visible below the snowline and the snow itself, though wet and
compact, is not underlain by ice. Yet the process of hollowing goes
forward visibly and in time will produce serrate forms. In neither case
is there the faintest sign of a bergschrund; the gradients seem so well
adjusted to the thickness and rate of movement of the snow from point to
point that the marginal crack found in many snowfields is absent.

The absence of bergschrunds is also noteworthy in many localities where
formerly glaciation took place. This is notoriously the case in the
summit zone of the Cordillera Vilcapampa, where the accumulating snows
of the steep cirque walls tumble down hundreds of feet to gather into
prodigious snowbanks or to form névé fields or glaciers. From the
converging walls the snowfalls keep up an intermittent bombardment of
the lower central snow masses. It is safe to say that if by magic a
bergschrund could be opened on the instant, it would be closed almost
immediately by the impetus supplied by the falling snow masses. The
explanation appears to be that the thicker snow and névé concentrated at
the bottom of the cirque results in a corresponding concentration of
action and effect; and cirque development goes on without reference to a
bergschrund. The chief attraction of the bergschrund hypothesis lies in
the concentration of action at the foot of the cirque wall. But in the
thickening of the snow far beyond the minimum thickness required for
motion at the base of the cirque wall and its change of function with
transformation into névé, we need invoke no other agent. If a
bergschrund forms, its action may take place at the foot of the cirque
wall or high up on the wall, and yet _sapping at the foot of the wall_
continue.

[Illustration: THE YALE PERUVIAN EXPEDITION OF 1911

HIRAM BINGHAM DIRECTOR

LAMBRAMA QUADRANGLE]

From which we conclude (1) that where frost action occurs at the bottom
of a bergschrund opening to the foot of the cirque wall it aids in the
retreat of the wall; (2) that a sapping action takes place at this point
whether or not a bergschrund exists and that bergschrund action is not a
_necessary_ part of cirque formation; (3) that when a more or less
persistent bergschrund opens on the cirque wall above its foot it tends
to develop a schrundline with a marked terrace below it; (4) that
schrundlines are best developed in the mature stages of topographic
development in the glacial cycle; (5) that the varying rates of snow,
névé, and ice motion at a valley head are the _persistent_ features to
which we must look for topographic variations; (6) that the hypothesis
here proposed is applicable to all cases whether they involve the
presence of snow or névé or ice or any combination of these, and whether
bergschrunds are present or not; and (7) at the same time affords a
reasonable explanation for such variations in forms as the compound
cirque with its schrundline and terrace, the unbroken cirque wall, the
notched cirque, and the recessed, snow-covered mountain slopes
unaffected by ice.

ASYMMETRICAL CREST LINES AND ABNORMAL VALLEY PROFILES IN THE CENTRAL
ANDES

To prove that under similar conditions glacial erosion may be greater
than subaërial denudation quantitative terms must be sought. Only these
will carry conviction to the minds of many opponents of the theory that
ice is a vigorous agent of erosion. Gilbert first showed in the Sierra
Nevada that headwater glaciers eroded more rapidly than nonglacial
agents under comparable topographic and structural conditions.[65] Oddly
enough none of the supporters of opposing theories have replied to his
arguments; instead they have sought evidence from other regions to show
that ice cannot erode rock to an important degree. In this chapter
evidence from the Central Andes, obtained in 1907 and 1911, will be
given to show the correctness of Gilbert’s proposition.

The data will be more easily understood if Gilbert’s argument is first
outlined. On the lower slopes of the glaciated Sierra Nevada asymmetry
of form resulted from the presence of ice on one side of each ridge and
its absence on the other (Fig. 200). The glaciers of these lower ridges
were the feeblest in the entire region and were formed on slopes of
small extent; they were also short-lived, since they could have existed
only when glacial conditions had reached a maximum. Let the broken line
in the upper part of the figure represent the preglacial surface and
the solid line beneath it the present surface. It will not matter what
value we give the space between the two lines on the left to express
nonglacial erosion, since had there been no glaciers it would be the
same on both sides of the ridge. The feeble glacier occupying the
right-hand slope was able in a very brief period to erode a depression
far deeper than the normal agents of denudation were able to erode in a
much longer period, i.e., during all of interglacial and postglacial
time. Gilbert concludes: “The visible ice-made hollows, therefore,
represent the local excess of glacial over nonglacial conditions.”

[Illustration: FIG. 200--Diagrammatic cross-section of a ridge glaciated
on one side only; with hypothetical profile (broken line) of preglacial
surface.]

[Illustration: FIG. 201--Postglacial volcano recessed on shady southern
side by the process of nivation. Absolute elevation 18,000 feet (5,490
m.), latitude 14° S., Maritime Cordillera, Peru.]

In the Central Andes are many volcanic peaks and ridges formed since the
last glacial epoch and upon them a remarkable asymmetry has been
developed. Looking southward one may see a smoothly curved, snow-free,
northward-facing slope rising to a crest line which appears as regular
as the slope leading to it. Looking northward one may see by contrast
(Fig. 194) sharp ridges, whose lower crests are serrate, separated by
deeply recessed, snow-filled mountain hollows. Below this highly
dissected zone the slopes are smooth. The smooth slope represents the
work of water; the irregular slopes are the work of snow and ice. The
relation of the north and south slopes is diagrammatically shown in Fig.
201.

To demonstrate the erosive effects of snow and ice it must be shown: (1)
that the initial slopes of the volcanoes are of postglacial age; (2)
that the asymmetry is not structural; (3) that the snow-free slopes have
not had special protection, as through a more abundant plant cover, more
favorable soil texture, or otherwise.

Proof of the postglacial origin of the volcanoes studied in this
connection is afforded: (1) by the relation of the flows and the ash and
cinder beds about the bases of the cones to the glacial topography; (2)
by the complete absence of glacial phenomena below the present snowline.
Ascending a marginal valley (Fig. 202), one comes to its head, where two
tributaries, with hanging relations to the main valley, come down from a
maze of lesser valleys and irregular slopes. Glacial features of a
familiar sort are everywhere in evidence until we come to the valley
heads. Cirques, reversed grades, lakes, and striæ are on every hand. But
at altitudes above 17,200 feet, recent volcanic deposits have over large
areas entirely obscured the older glacial topography. The glacier which
occupied the valley of Fig. 202 was more than one-quarter of a mile
wide, the visible portion of its valley is now over six miles long, but
the extreme head of its left-hand tributary is so concealed by volcanic
material that the original length of the glacier cannot be determined.
It was at least ten miles long. From this point southward to the border
of the Maritime Cordillera no evidence of past glaciation was observed,
save at Solimana and Coropuna, where slight changes in the positions of
the glaciers have resulted in the development of terminal moraines a
little below the present limits of the ice.

From the wide distribution of glacial features along the northeastern
border of the Maritime Cordillera and the general absence of such
features in the higher country farther south, it is concluded that the
last stages of volcanic activity were completed in postglacial time. It
is equally certain, however, that the earlier and greater part of the
volcanic material was ejected before glaciation set in, as shown by the
great depth of the canyons (over 5,000 feet) cut into the lava flows, as
contrasted with the relatively slight filling of coarse material which
was accumulated on their floors in the glacial period and is now in
process of dissection. Physiographic studies throughout the Central
Andes demonstrate both the general distribution of this fill and its
glacial origin.

So recent are some of the smaller peaks set upon the lava plateau that
forms the greater part of the Maritime Cordillera, that the snows massed
on their shadier slopes have not yet effected any important topographic
changes. The symmetrical peaks of this class are in a few cases so very
recent that they are entirely uneroded. Lava flows and beds of tuff
appear to have originated but yesterday, and shallow lava-dammed lakes
retain their original shore relations. In a few places an older
topography, glacially modified, may still be seen showing through a
veneer of recent ash and cinder deposits, clear evidence that the
loftier parts of the lava plateau were glaciated before the last
volcanic eruption.

The asymmetry of the peaks and ridges in the Maritime Cordillera cannot
be ascribed to the manner of eruption, since the contrast in declivity
and form is persistently between northern and southern slopes. Strong
and persistent winds from a given direction undoubtedly influence the
form of volcanoes to at least a perceptible degree. In the case in hand
the ejectamenta are ashes, cinders, and the like, which are blown into
the air and have at least a small component of motion down the wind
during both their ascent and descent. The _prevailing_ winds of the high
plateaus are, however, easterly and the strongest winds are from the
west and blow daily, generally in the late afternoon. Both wind
directions are at right angles to the line of asymmetry, and we must,
therefore, rule out the winds as a factor in effecting the slope
contrasts which these mountains display.

It remains to be seen what influence a covering of vegetation on the
northern slopes might have in protecting them from erosion. The northern
slopes in this latitude (14° S.) receive a much greater quantity of heat
than the southern slopes. Above 18,000 feet (5,490 m.) snow occurs on
the shady southern slopes, but is at least a thousand feet higher on the
northern slopes. It is therefore absent from the northern side of all
but the highest peaks. Thus vegetation on the northern slopes is not
limited by snow. Bunch grass--the characteristic _ichu_ of the mountain
shepherds--scattered spears of smaller grasses, large ground mosses
called _yareta_, and lichens extend to the snowline. This vegetation,
however, is so scattered and thin above 17,500 feet (5,330 m.) that it
exercises no retarding influence on the run-off. Far more important is
the porous nature of the volcanic material, which allows the rainfall to
be absorbed rapidly and to appear in springs on the lower slopes, where
sheets of lava direct it to the surface.

The asymmetry of the north and south slopes is not, then, the result of
preglacial erosion, of structural conditions, or of special protection
of the northern slopes from erosion. It must be concluded, therefore,
that it is due to the only remaining factor--snow distribution. The
southern slopes are snow-clad, the northern are snow-free--in harmony
with the line of asymmetry. The distribution of the snow is due to the
contrasts between shade and sun temperatures, which find their best
expression in high altitudes and on single peaks of small extent.
Frankland’s observations with a black-bulb thermometer _in vacuo_ show
an increase in shade and sun temperatures contrasts of over 40° between
sea level and an elevation of 10,000 feet. Violle’s experiments show an
increase of 26 per cent in the intensity of solar radiation between 200
feet and 16,000 feet elevation. Many other observations up to 16,000
feet show a rapid increase in the difference between sun and shade
temperatures with increasing elevation. In the region herein described
where the snowline is between 18,000 and 19,000 feet (5,490 to 5,790 m.)
these contrasts are still further heightened, especially since the
semi-arid climate and the consequent long duration of sunshine and low
relative humidity afford the fullest play to the contrasting forces. The
coefficient of absorption of radiant energy by water vapor is 1,900
times that of air, hence the lower the humidity the more the radiant
energy expended upon the exposed surface and the greater the sun and
shade contrasts. The effect of these temperature contrasts is seen in a
canting of the snowline on individual volcanoes amounting to 1,500 feet
in extreme instances. The average may be placed at 1,000 feet.

The minimum conditions of snow motion and the bearing of the conclusions
upon the formation of cirques have been described in the chapters
immediately preceding. It is concluded that snow moves upon 20° slopes
if the snow is at least forty feet deep, and that through its motion
under more favorable conditions of greater depth and gradient and the
indirect effects of border melting there is developed a hollow occupied
by the snow. Actual ice is not considered to be a necessary condition of
either movement or erosion. We may at once accept the conclusion that
the invariable association of the cirques and steepened profiles with
snowfields proves that snow is the predominant modifying agent.

An argument for glacial erosion based on profiles and steep cirque walls
in a volcanic region has peculiar appropriateness in view of the
well-known symmetrical form of the typical volcano. Instead of varied
forms in a region of complex structure long eroded before the appearance
of the ice, we have here simple forms which immediately after their
development were occupied by snow. _Ever since their completion these
cones have been eroded by snow on one side and by water on the other._
If snow cannot move and if it protects the surface it covers, then this
surface should be uneroded. All such surfaces should stand higher than
the slopes on the opposite aspect eroded by water. But these assumptions
are contrary to fact. The slopes underneath the snow are deeply
recessed; so deeply eroded indeed, that they are bordered by steep
cliffs or cirque walls. The products of erosion also are to some extent
displayed about the border of the snow cover. In strong contrast the
snow-free slopes are so slightly modified that little of their original
symmetry is lost--only a few low hills and shallow valleys have been
formed.

The measure of the excess of snow erosion over water erosion is
therefore the difference between a northern or water-formed and a
southern or snow-formed profile, Fig. 200. This difference is also shown
in Fig. 201 and from it and the restored initial profiles we conclude
that the rate of water erosion is to that of nivation as 1:3. This ratio
has been derived from numerous observations on cones so recently formed
that the interfluves without question are still intact.

Thus far only those volcanoes have been considered which have been
modified by nivation. There are, however, many volcanoes which have been
eroded by ice as well as by snow and water. It will be seen at once that
where a great area of snow is tributary to a single valley, the snow
becomes compacted into névé and ice, and that it then erodes at a much
faster rate. Also a new force--plucking--is called into action when ice
is present, and this greatly accelerates the rate of erosion. While it
lies outside the limits of my subject to determine quantitatively the
ratio between water and ice action, it is worth pointing out that by
this method a ratio much in excess of 1:3 is determined, which even in
this rough form is of considerable interest in view of the arguments
based on the protecting influence of both ice and snow. I have, indeed,
avoided the question of ice erosion up to this point and limited myself
to those volcanoes which have been modified by nivation only, since the
result is more striking in view of the all but general absence of data
relating to this form of erosion.

[Illustration: FIG. 202--Graphic representation of amount of glacial
erosion during the glacial period. In the background are mature slopes
surmounted by recessed asymmetrical peaks. The river entrenched itself
below the mature slopes before it began to aggrade, and, when
aggradation set in, had cut its valley floor to a′-b′-c. By aggradation
the valley floor was raised to a-b while ice occupied the valley head.
By degradation the river has again barely lowered its channel to a′-b′,
the ice has disappeared, and the depression of the profile represents
the amount of glacial erosion.

a′-b′-c = preglacial profile.

a-b-d-c = present profile.

b′-d-c-b = total ice erosion in the glacial period.

a-b = surface of an alluvial valley fill due to
excessive erosion at valley head.

b-b′ = terminal moraine.

d-c = cirque wall.

e, e′ e″ = asymmetrical summits.]

[Illustration: FIG. 203--A composite sketch to represent general
conditions in the Peruvian Andes. In order to have the actual facts
represented the profiles of this figure were taken from the accompanying
topographic sheets. The main depression on the right and the
corresponding depression of the tributary profiles bear out most
strikingly the conclusions concerning the erosive power of the ice. At
_A_ and _B_ the spurs have been cut off to exhibit the profiles of
tributary valleys. At _2_ and _3_ were tributary glaciers of such size
that they entered the main valley at grade. Lesser tributaries had
floors elevated above those they joined and now have a hanging
character, as just above _2_. _D_ is a matterhorn; _C_ is deeply
recessed by cirques; _E_ represents a peak just below the limit of
glaciation. At _F_ are the undissected post-mature slopes of an earlier
cycle of erosion. _G_ lies on the steep lower slopes formed during the
canyon cycle of erosion. The down-cutting of the stream in the canyon
cycle was generally checked by glaciation and was superseded by
aggradation.]

If we now turn to the valley profiles of the glaciated portions of the
Peruvian Andes, we shall see the excess of ice over water erosion
expressed in a manner equally convincing. To a thoughtful person it is
one of the most remarkable features of any glaciated region that the
flattest profiles, the marshiest valley flats, and the most strongly
meandering stretches of the streams should occur near the heads of the
valleys. The mountain shepherds recognize this condition and drive
their flocks up from the warmer valley into the mountain recesses,
confident that both distance and elevation will be offset by the
extensive pastures of the finest _ichu_ grass. Indeed, to be near the
grazing grounds of sheep and llamas which are their principal means of
subsistence, the Indians have built their huts at the extraordinarily
lofty elevations of 16,000 to 17,000 feet.

An examination of a large number of these valleys and the plotting of
their gradients discloses the striking fact that the heads of the
valleys were deeply sunk into the mountains. It is thus possible by
restoring the preglacial profiles to measure with considerable certainty
the excess of ice over water erosion.

The results are graphically expressed in Fig. 202. It will be seen that
until glacial conditions intervened the stream was flowing on a rock
floor. During the whole of glacial time it was aggrading its rock floor
below _b′_ and forming a deep valley fill. A return to warmer and drier
conditions led to the dissection of the fill and this is now in
progress. The stream has not yet reached its preglacial profile, but it
has almost reached it. We may, therefore, say that the preglacial valley
profile below _b′_ fixes the position of the present profile just as
surely as if the stream had been magically halted in its work at the
beginning of the period of glaciation. There, _b′-d-c-b_ represents the
amount of ice erosion. To be sure the line _b-c_ is inference, but it is
reasonable inference and, whatever position is assigned to it, it cannot
be coincident with _b′-d_, nor can it be anywhere near it. The break in
the valley profile at _b′_ is always marked by a terminal moraine,
regardless of the character of the rock. This is not an accidental but a
causal association. It proves the power of the ice to erode. In glacial
times it eroded the quantity _b-c-d-b′_. This is not an excess of ice
over water erosion, but an absolute measure of ice erosion, since
_a′-b′_ has remained intact. The only possible error arises from the
position assigned _b-c_, and even if we lower it to _b-c′_ (for which we
have no warrant but extreme conservatism) we shall still have left
_b′-c′-d-b_ as a striking value for rock erosion (plucking and abrasion)
by a valley glacier.

A larger diagram, Fig. 203, represents in fuller detail the topographic
history of the Andes of southern Peru and the relative importance of
glaciation. The broad spurs with grass-covered tops that end in steep
scarps are in wonderful contrast to the serrate profiles and truncated
spurs that lie within the zone of past glaciation. In the one case we
have minute irregularities on a canyon wall of great dimensions; in the
other, more even walls that define a glacial trough with a flat floor.
Before glaciation on a larger scale had set in the right-hand section of
the diagram had a greater relief. It was a residual portion of the
mountain and therefore had greater height also. Glaciers formed upon it
in the Ice Age and glaciation intensified the contrast between it and
the left-hand section; not so much by intensifying the relief as by
diversifying the topographic forms.

[Illustration: FIG. 204--Topographic map of the Andes between Abancay
and the Pacific Coast at Camaná. Compiled from the seven accompanying
topographic sheets (see Contents, p. xi). Scale 1:1,000,000. Contour
interval 1,000 feet. Longitude west of Greenwich. The Central Ranges of
the Maritime Cordillera are not confined to the area covered by these
names. In the one case the term includes all the ranges between Lambrama
and Huichihua; in the other case, the peaks and ranges from 14° 30′ S.
to Mt. Coropuna.]

APPENDIX A

SURVEY METHODS EMPLOYED IN THE CONSTRUCTION OF THE SEVEN ACCOMPANYING
TOPOGRAPHIC SHEETS

BY KAI HENDRIKSEN, TOPOGRAPHER

The main part of the topographical outfit consisted of (1) a 4-inch
theodolite, Buff and Buff, the upper part detachable, (2) an 18 x 24
inch plane-table with Johnson tripod and micro-meteralidade. These
instruments were courteously loaned the expedition by the U. S. Coast
and Geodetic Survey and the U. S. Geological Survey respectively.

The method of survey planned was a combination of graphic triangulation
and traverse with the micro-meteralidade. All directions were plotted on
the plane-table which was oriented by backsight; distances were
determined by the micro-meteralidade or triangulation, or both combined;
and elevations were obtained by vertical angles. Finally, astronomical
observations, usually to the sun, were taken at intervals of about 60
miles for latitude and azimuth to check the triangulation. No
observations were made for differences in longitude because this would
probably not have given any reliable result, considering the time and
instruments at our disposal. Because the survey was to follow very
closely the seventy-third meridian west of Greenwich, directions and
distances, checked by latitude and azimuth observations, undoubtedly
afforded far better means of determining the longitude than time
observations. In other words, the time observations made in connection
with azimuth observations were not used for computing longitudinal
differences. Absolute longitude was taken from existing observations of
principal places.

Principal topographical points were located by from two to four
intersections from the triangulation and plane-table stations; and
elevations were determined by vertical angle measurements. Whenever
practicable, the contours were sketched in the field; the details of the
topography otherwise depend upon a great number of photographs taken by
Professor Bowman from critical stations or other points which it was
possible to locate on the maps.

CROSS-SECTION MAP FROM ABANCAY TO CAMANÁ AT THE PACIFIC OCEAN

Seven sheets. Scale, 1:125,000; contour interval, 200 feet. Datum is
mean sea level. Astronomical control: 5 latitude and 5 azimuth
observations as indicated on the accompanying topographic sheets.

On September 10th, returning from a reconnaissance survey of the
Pampaconas River, I joined Professor Bowman’s party, Dr. Erving acting
as my assistant. We crossed the Cordillera Vilcapampa and the Canyon of
the Apurimac and after a week’s rest at Abancay started the topographic
work near Hacienda San Gabriel south of Abancay. Working up the deep
valley of Lambrama, observations for latitude and azimuth were made
midway between Hacienda Matara and Caypi.

On October 4th we made our camp in newly fallen snow surrounded by
beautiful glacial scenery. The next day on the high plateau, we passed
sharp-crested glaciated peaks; a heavy thunder and hail storm broke out
while I occupied the station at the pass, the storm continuing all the
afternoon--a frequent occurrence. The camp was made 6 miles farther on,
and the next morning I returned to finish the latter station. I
succeeded in sketching the detailed topography just south of the pass,
but shortly after noon, a furious storm arose similar to the one the day
before, and made further topographic work impossible; to get connection
farther on I patiently kept my eye to the eye-piece for more than an
hour after the storm had started, and was fortunate to catch the station
ahead in a single glimpse. I had a similar experience some days later at
station 16,079, Antabamba Quadrangle, on the rim of the high-level puna,
the storm preventing all topographic work and barely allowing a single
moment in which to catch a dim sight of the signals ahead while I kept
my eye steadily at the telescope to be ready for a favorable break in
the heavy clouds and hail.

At Antabamba we got a new set of Indian carriers, who had orders to
accompany us to Cotahuasi, the next sub-prefectura. Raimondi’s map
indicates the distance between the two cities to be 35 miles, but
although nothing definite was stated, we found out in Antabamba that the
distance was considerably longer, and moreover that the entire route lay
at a high altitude.

From the second day out of Antabamba until Huaynacotas was in sight in
the Cotahuasi Canyon, a distance of 50 miles, the route lay at an
altitude of from 16,000 to 17,630 feet, taking in 5 successive camps at
an altitude from 15,500 to 17,000 feet; 12 successive stations had the
following altitudes:

16,379 feet
16,852 "
17,104 "
17,559 "
17,675 " --highest station occupied.
17,608 "
17,633 "
16,305 "
17,630 "
17,128 "
16,794 "
16,260 "

The occupation of these high stations necessitated a great deal of
climbing, doubly hard in this rarefied air, and often on volcanoes with
a surface consisting of bowlders and ash and in the face of violent
hailstorms that made extremely difficult the task of connecting up
observations at successive stations.

At Cotahuasi a new pack-train was organized, and on October 25th I
ventured to return alone to the high altitudes in order to continue the
topography at the station at 17,633 feet on the summit of the Maritime
Cordillera. Dr. Erving was obliged to leave on October 18th and
Professor Bowman left a week later in order to carry out his plans for a
physiographic study of the coast between Camaná and Mollendo. Philippi
Angulo, a native of Taurisma, a town above Cotahuasi, acted as majordomo
on this journey. Knowing the trail and the camp sites, I was able to
pick out the stations ahead myself, and made good progress, returning to
Cotahuasi on October 29th, three or four days earlier than planned. From
Cotahuasi to the coast I had the assistance of Mr. Watkins. The most
trying part of the last section of high altitude country was the great
Pampa Colorada, crowned by the snow-capped peaks of Solimana and
Coropuna, reaching heights of 20,730 and 21,703 feet respectively. The
passing of this pampa took seven days and we arrived at Chuquibamba on
November 9th. Two circumstances made the work on this stretch peculiarly
difficult--the scarcity of camping places and the high temperature in
the middle of the day, which heated the rarefied air to a degree that
made long-distance shots very strenuous work for the eyes. Although our
base signals were stone piles higher than a man, I was often forced to
keep my eye to the telescope for hours to catch a glimpse of the
signals; lack of time did not allow me to stop the telescope work in the
hottest part of the day.

The top of Coropuna was intersected from the four stations: 16,344,
15,545, 16,168, and 16,664 feet elevation, the intersections giving a
very small triangular error. The elevation of Mount Coropuna’s high peak
as computed from these 4 stations is:

21,696 feet
21,746 "
21,714 "
21,657 "
------
Mean elevation 21,703 feet above sea level.

The elevation of Coropuna as derived from these four stations has thus a
mean error of 18 feet (method of least squares) while the elevation of
each of the four stations as carried up from mean sea level through 25
stations--vertical angles being observed in both directions--has an
estimated mean error of 30 feet. The result of this is a mean error of
35 feet in Coropuna’s elevation above mean sea level.

The latitude is 15° 31′ 00″ S.; the longitude is 72° 42′ 40″ W. of
Greenwich, the checking of these two determinations giving a result
unexpectedly close.

On November 11th azimuth and latitude observations were taken at
Chuquibamba and two days later we arrived at Aplao in the bottom of the
splendid Majes Valley. In the northern part of this valley I was
prevented from doing any plane-table work in the afternoons of four
successive days. A strong gale set in each noon raising a regular
sandstorm, that made seeing almost impossible, and blowing with such a
velocity that it was impossible to set up the plane-table.

From Hacienda Cantas to Camaná we had to pass the western desert for a
distance of 45 miles. We were told that on the entire distance there was
only one camping place. This was at Jaguey de Majes, where there was a
brook with just enough water for the animals but no fodder. Thus we
faced the necessity of carrying water for ten men and fodder for 14
animals in excess of the usual cargo; and we were unable to foretell how
many days the topography over the hot desert would require.

Although plane-table work in the desert was impossible at all except in
the earliest and latest hours of the day, we made regular progress. We
camped three nights at Jaguey and arrived on the fourth day at Las
Lomas.

The next morning, on November 23rd, at an elevation of 2178 feet near
the crest of the Coast Range, we were repaid for two months of laborious
work by a glorious view of the Pacific Ocean and of the city of Camaná
with her olive gardens in the midst of the desert sand.

The next day I observed latitude and azimuth at Camaná and in the night
my companion and assistant Mr. Watkins and I returned across the desert
to the railroad at Vitor.

CONCLUSIONS

The planned methods were followed very closely. In two cases only the
plane-table had to be oriented by the magnetic needle, the backsights
not being obtainable because of the impossibility of locating the last
station, passing Indians having removed the signals.

In one case only the distance between two stations had to be determined
by graphic triangulation exclusively, the base signals having been
destroyed. Otherwise graphic triangulation was used as a check on
distances.

Vertical angles were always measured in both directions with the
exception of the above-mentioned cases.

Observations for azimuth were always taken to the sun before and after
noon. The direction used in the azimuth observation was also taken with
the prismatic compass. The mean of the magnetic declination thus found
is: East 8° 30′ plus.

Observations for latitude were taken to the sun by the method of
circum-meridian altitudes, except at the town of Vilcabamba where star
observations were taken.

As a matter of course, observations to the sun are not so exact as star
observations, especially in low latitudes where one can expect to
observe the near zenith. However, working in high altitudes for long
periods, moving camp every day and often arriving at camp 2 to 4 hours
after sunset, I found it essential to have undisturbed rest at night. It
was beyond my capacity to spend an hour or two of the night in finding
the meridian and in making the observation. Furthermore, the astronomic
observations were to check the topography mainly, the latter being the
most exact method with the outfit at hand.

The following table contains the comparisons between the latitude
stations as located on the map and by observation:

Map Observation
Camaná Quadrangle S 16° 37′ 34″ 16° 37′ 34″[66]
Coropuna, station 9,691S 15° 48′ 30″ (15° 51′ 44″)
Cotahuasi, " 12,588S 15° 11′ 40″ 15° 12′ 30″
La Cumbre, " 16,852S 14° 28′ 10″ 14° 29′ 46″
Lambrama, " 8,341S 13° 43′ 18″ 13° 43′ 14″

The other observations, with the exception of the one on the Coropuna
Quadrangle, check probably as well as can be expected with the small and
light outfit which we used, and under the exceptionally hard conditions
of work. The observation on the Coropuna Quadrangle just south of
Chuquibamba is, however, too much out. An explanation for this is that
the meridian zenith distance was 1° 23′ 12″ only (in this case the exact
formula was used in computing). Of course, an error or an accumulation
of errors might have been made in the distances taken by the
micrometer-alidade, but the first cause of error mentioned is the more
probable, and this is indicated also by the fact that the location on
the top of Mount Coropuna checks closely with the one determined in an
entirely independent way by the railroad engineers.

For the cross-section map from Abancay to Camaná, the following
statistics are desirable:

Micrometer traverse and graphic triangulation, with contours, field
scale 1:90,000.

Total time required, days 40.5
Average distance per days in miles 7.5
Average number of plane-table stations occupied per day 1.5
Average area per day in square miles 38.
Located points per square mile 0.25
Approximate elevations in excess of above, per square mile 0.25
Highest station occupied, feet above sea level 17,675.
Highest point located, feet above sea level 21,703.

APPENDIX B

FOSSIL DETERMINATIONS

A few fossil collections were gathered in order that age determinations
might be made. With the following identifications I have included a few
fossils (I and II) collected by W. R. Rumbold and put into my hands in
1907. The Silurian is from a Bolivian locality south of La Paz but in
the great belt of shales, slates, and schists which forms one of the
oldest sedimentary series in the Eastern Andes of Peru as well as
Bolivia. While no fossils were found in this series in Peru the rocks
are provisionally referred to the Silurian. Fossil-bearing Carboniferous
overlies them but no other indication of their age was obtained save
their general position in the belt of schists already mentioned. I am
indebted to Professor Charles Schuchert of Yale University for the
following determinations.

I. _Silurian_

San Roque Mine, southwest slope of Santa Vela Cruz, Canton Ichocu, Province
Inquisivi, Bolivia.

Sent by William R. Rumbold in 1907.

_Climacograptus?_
_Pholidops trombetana_ Clarke?
_Chonetes striatellus_ (Dalman).
_Atrypa marginalis_ (Dalman)?
_Cœlospira_ n. sp.
_Ctenodonta_, 2 or more species.
_Hyolithes._
_Klœdenia._
_Calymene?_
_Dalmanites_, a large species with a terminal tail spine.
_Acidaspis._

These fossils indicate unmistakably Silurian and probably Middle
Silurian. As all are from blue-black shales, brachiopods are the rarer
fossils, while bivalves and trilobites are the common forms. The faunal
aspect does not suggest relationship with that of Brazil as described by
J. M. Clarke and not at all with that of North America. I believe this
is the first time that Silurian fossils have been discovered in the high
Andes.

II. LOWER DEVONIAN

Near north end of Lake Titicaca.

_Leptocœlia flabellites_ (Conrad), very common.
_Atrypa reticularis_ (Linnæus)?

This is a part of the well-known and widely distributed Lower Devonian
fauna of the southern hemisphere.

III. _Upper Carboniferous_

All of the Upper Carboniferous lots of fossils represent the well-known
South American fauna first noted by d’Orbigny in 1842, and later added
to by Orville Derby. The time represented is the equivalent of the
Pennsylvanian of North America.

Huascatay between Pasaje and Huancarama.

Crinoidal limestone.
Trepostomata Bryozoa.
_Polypora._ Common.
_Streptorhynchus hallianus_ Derby. Common.
_Chonetes glaber_ Geinitz. Rare.
_Productus humboldti_ d’Orb. Rare.
" _cora_ d’Orb. Rare.
" _chandlessii_ Derby.
" sp. undet. Common.
" sp. undet. "
_Spirifer condor_ d’Orb. Common.
_Hustedia mormoni_ (Marcou). Rare.
_Seminula argentea_ (Shepard). "

Pampaconas, Pampaconas valley near Vilcabamba.

_Lophophyllum?_
_Rhombopora_, etc.
_Productus._
_Camarophoria._ Common.
_Spirifer condor_ d’Orb.
_Hustedia mormoni_ (Marcou).
_Euomphalus._ Large form.

Pongo de Mainique. Extreme eastern edge of Peruvian Cordillera.

_Lophophyllum._
_Productus chandlessii_ Derby.
" _cora_ d’Orb.
_Orthotetes correanus_ (Derby).
_Spirifer condor_ d’Orb.

River bowlders and stones of Urubamba river, just beyond eastern edge of
Cordillera at mouth of Ticumpinea river. (Detached and transported by stream
action from the Upper Carboniferous at Pongo de Mainique.)

Mostly Trepostomata Bryozoa.
Many _Productus_ spines.
_Productus cora_ d’Orb.
_Camarophoria_. Same as at Pampaconas.
_Productus_ sp. undet.

Cotahuasi A.

_Lophophyllum._
_Productus peruvianus_ d’Orb.
" sp. undet.
_Camarophoria._
_Pugnax_ near _utah_ (Marcou).
_Seminula argentea_ (Shepard)?

Cotahuasi B.

_Productus cora_ d’Orb.
" near _semireticulatus_ (Martin).

IV. _Comanchian or Lower Cretaceous_

Near Chuquibambilla.

_Pecten_ near _quadricostatus_ Sowerby.
Undet. bivalves and gastropods.
The echinid _Laganum? colombianum_ d’Orb. A clypeasterid.

This Lower Cretaceous locality is evidently of the same horizon as that
of Colombia illustrated by d’Orbigny in 1842 and described on pages
63-105.

APPENDIX C

KEY TO PLACE NAMES

Abancay, town, lat. 12° 35′, Figs. 20, 204.

Abra Tocate, pass, between Yavero and Urubamba valleys,
leaving latter at Rosalina, (Fig. 8).
_See also_ Fig. 55.

Anta, town, lat. 13° 30′, Fig. 20.

Antabamba, town, lat. 14° 20′, Figs. 20, 204.

Aplao, town, lat. 16°, Figs. 20, 204.

Apurimac, river, Fig. 20.

Arequipa, town, lat. 16° 30′, Fig. 66.

Arica, town, northern Chile, lat. 18° 30′.

Arma, river, tributary of Apurimac, lat. 13° 25′, (Fig. 20);
tributary of Ocoña, lat. 15° 30′, (Fig. 20).

Arma, village, lat. 13° 15′, Fig. 20.
_See also_ Fig. 140.

Auquibamba, hacienda, lat. 13° 40′, Fig. 204.

Callao, town, lat. 12°, Fig. 66.

Camaná, town, lat. 16° 40′, Figs. 20, 66, 204.

Camisea, river, tributary of Urubamba entering from right, lat. 11° 15′.

Camp 13, lat. 14° 30′.

Cantas, hacienda, lat. 16° 15′, Fig. 204.

Caraveli, town, lat. 16°, Fig. 66.

Catacaos, town, lat. 5° 30′, Fig. 66.

Caylloma, town and mines, lat. 15° 30′, Fig. 66.

Caypi, village, lat. 13° 45′.

Central Ranges, lat. 14°, Fig. 20.
_See also_ Fig. 157.

Cerro Azul, town, lat. 13°, Fig. 66.

Chachani, mt., overlooking Arequipa, lat. 16° 30′, (Fig. 66).

Chaupimayu, river, tributary of Urubamba entering at Sahuayaco, _q.v._

Chili, river, tributary of Vitor River, lat. 16° 30′, (Fig. 66).

Chinche, hacienda, Urubamba Valley above Santa Ana, lat. 13°, (Fig. 20).

Chira, river, lat. 5°, Fig. 66.

Choclococha, lake, lat. 13° 30′, Figs. 66, 68.

Choqquequirau, ruins, canyon of Apurimac above junction of Pachachaca
River, lat. 13° 25′, (Fig. 20).

Choquetira, village, lat. 13° 20′, Fig. 20.
_See also_ Fig. 136.

Chosica, village, lat. 12°, Fig. 66.

Chuquibamba, town, lat. 15° 50′, Figs. 20, 204.

Chuquibambilla, village, lat. 14°, Figs. 20, 204.

Chuquito, pass, Cordillera Vilcapampa between Arma and Vilcabamba
valleys, lat. 13° 10′, (Fig. 20).
_See also_ Fig. 139.

Coast Range, Figs. 66, 204.

Cochabamba, city, Bolivia, lat. 17° 20′, long. 66° 20′.

Colorada, pampa, lat. 15° 30′, Fig. 204.

Colpani, village, lower end of Canyon of Torontoy (Urubamba River),
lat. 13° 10′. _See_ Fig. 158.

Copacavana, village, Bolivia, lat. 16° 10′, long. 69° 10′.

Coribeni, river, lat. 12° 40′, Fig. 8.

Coropuna, mt., lat. 15° 30′, Figs. 20, 204.

Corralpata, village, Apurimac Valley near Incahuasi.

Cosos, village, lat. 16°, Fig. 204.

Cotabambas, town, Apurimac Valley, lat. 13° 45′, (Fig. 20).

Cotahuasi, town, lat. 15° 10′, Figs. 20, 204.

Cuzco, city, lat. 13° 30′, Fig. 20.

Echarati, hacienda, on the Urubamba River between Santa Ana and
Rosalina, lat. 12° 40′.
_See_ inset map, Fig. 8, _and also_ Fig. 54.

Huadquiña, hacienda, Urubamba River above junction with Vilcabamba,
lat. 13° 10′, (Fig. 20).
_See also_ Fig. 158.

Huadquirca, village, lat. 14° 15′, Figs. 20, 204.

Huaipo, lake, north of Anta, lat. 13° 25′, (Fig. 20).

Huambo, village, left bank Pachachaca River between Huancarama
and Pasaje, lat. 13° 35′, (Fig. 20).

Huancarama, town, lat. 13° 40′, Fig. 20.

Huancarqui, village, lat. 16° 5′, Fig. 204.

Huascatay, village, left bank of Apurimac above Pasaje,
lat. 13° 30′, (Fig. 20).

Huaynacotas, village, lat. 15° 10′, Fig. 204.

Huichihua, village, lat. 14° 10′, Fig. 204.

(Tablazo de) Ica, plateau, lat. 14°-15° 30′, Fig. 66.

Ica, town, lat. 14°, Figs. 66, 67.

Incahuasi, village, lat. 13° 20′, Fig. 20.

Iquique, town, northern Chile, lat. 20° 15′.

(Pampa de) Islay, south of Vitor River, (Fig. 66).

Jaguey, village, Pampa de Sihuas, _q.v._

La Joya, pampa, station on Mollendo-Puno R.R., 16° 40′, (Fig. 66).

Lambrama, village, lat. 12° 50′, Fig. 20.

Lima, city, lat. 12°, Fig. 66.

Machu Picchu, ruins, gorge of Torontoy, _q.v._, lat. 13° 10′.

Majes, river, Fig. 204.

Manugali, river, tributary of Urubamba entering from left
above Puviriari River, lat. 12° 20′, (Fig. 8).

Maritime Cordillera, Fig. 204.

Matara, village, lat. 14° 20′, Fig. 204.

(El) Misti, mt., lat. 16° 30′, Fig. 66.

Mollendo, town, lat. 17°, Fig. 66.

Moquegua, town, lat. 17°, Fig. 66.

Morococha, mines, lat. 11° 45′, Fig. 66.

Mulanquiato, settlement, lat. 12° 10′, Fig. 8.

Occobamba, river, uniting with Yanatili, _q.v._

Ocoña, river, lat. 15°-16° 30′, Figs. 20, 66.

Ollantaytambo, village. Urubamba River below Urubamba town,
lat. 13° 15′, (Fig. 20), _and see_ inset map, Fig. 8.

Pabellon, hacienda, Urubamba River above Rosalina, (Fig. 20).
_See also_ Fig. 55.

Pacasmayo, town, lat. 7° 30′, Fig. 66.

Pachatusca (Pachatusun), mt., overlooking Cuzco to northeast, lat. 13° 30′.

Pachitea, river, tributary of Ucayali entering from left, lat. 8° 50′.

Paita, town, lat. 5°, Fig. 66.

Pampacolea, village, south of Coropuna, _q.v._

Pampaconas, river, known in lower course as Cosireni,
tributary of Urubamba River, (Fig. 8).
Source in Cordillera Vilcapampa west of Vilcabamba.

Pampas, river, tributary of Apurimac entering from left, lat. 13° 20′.

Panta, mt., Cordillera Vilcapampa, northwest of Arma, lat. 13° 15′, (Fig. 20).
_See also_ Fig. 136.

Panticalla, pass, Urubamba Valley above Torontoy, lat. 13° 10′.

Pasaje, hacienda and ferry, lat. 13° 30′, Fig. 20.

Paucartambo (Yavero), river, _q.v._

Paucartambo, town, head of Paucartambo (Yavero) River,
lat. 13° 20′, long. 71° 40′. Inset map, Fig. 8.

Pichu-Pichu, mt., overlooking Arequipa, lat. 16°, (Fig. 66).

Pilcopata, river, tributary of Upper Madre de Dios
east of Paucartambo, lat. 13°.

Piñi-piñi, river, tributary of Upper Madre de Dios
east of Paucartambo, lat. 13°.

Pisco, town, lat. 14°, Fig. 66.

Piura, river, lat. 5°-6°, Fig. 66.

Piura, town, lat. 5° 30′, Fig. 66.

Pomareni, river, lat. 12°, Fig. 8.

Pongo de Mainique, rapids, lat. 12°, Fig. 8.

Pucamoco, hacienda, Urubamba River, between Santa Ana and Rosalina, (Fig. 20).

Puquiura, village, lat. 13° 5′, Fig. 20.
_See also_ Fig. 158. Distinguish Puqura in Anta basin near Cuzco.

Puqura, village, Anta basin, east of Anta, lat. 13° 30′, (Fig. 20).

Quilca, town, lat. 16° 40′, Fig. 66.

Quillagua, village, northern Chile, lat. 21° 30′, long. 69° 35′.

Rosalina, settlement, lat. 12° 35′, Fig. 8.
_See also_ Fig. 20.

Sahuayaco, hacienda, Urubamba Valley above Rosalina, (Fig. 20).
_See also_ Fig. 55.

Salamanca, town, lat. 15° 30′, Fig. 20.

Salaverry, town, lat. 8°, Fig. 66.

Salcantay, mt., lat. 13° 20′, Fig. 20.

San Miguel, bridge, canyon of Torontoy near Machu Picchu, lat. 13° 10′.

Santa Ana, hacienda, lat. 12° 50′, Fig. 20.

Santa Ana, river, name applied to the Urubamba in the
region about hacienda Santa Ana.

Santa Lucia, mines, lat. 16°, Fig. 66.

Santo Anato, hacienda, La Sama’s hut, 12° 35′, Fig. 8.

Sihuas, Pampa de, lat. 16° 30′, Fig. 204.

Sillilica, Cordillera, east of Iquique, northern Chile.

Sintulini, rapids of Urubamba River above junction of
Pomareni, lat. 12° 10′, (Fig. 8).

Sirialo, river, lat. 12° 40′, Fig. 8.

Soiroccocha, mt., Cordillera Vilcapampa north of Arma,
lat. 13° 15′, (Fig. 20).

Solimana, mt., lat. 15° 20′, Fig. 204.

Soray, mt., Cordillera Vilcapampa, southeast of Mt. Salcantay,
lat. 13° 20′, (Fig. 20).

Sotospampa, village, near Lambrama, lat. 13° 50′, (Fig. 204).

Sullana, town, Chira River, lat. 5°, (Fig. 66).

Taurisma, village, lat. 15° 10′, Fig. 204.

Ticumpinea, river, tributary of Urubamba entering from right
below Pongo de Mainique, lat. 11° 50′, (Fig. 8).

Timpia, river, tributary of Urubamba entering from right, lat. 11° 45′.

Tono, river, tributary of Upper Madre de Dios, east of Paucartambo, lat. 13°.

Torontoy, canyon of the Urubamba between the villages of Torontoy
and Colpani, lat. 13° 10′-13° 15′.

Torontoy, village at the head of the canyon of the same name, lat. 13° 15′.
_See_ inset map, Fig. 8.

Tumbez, town, lat. 4° 30′, Fig. 66.

Tunari, Cerro de, mt., northwest of Cochabamba, _q.v._

Urubamba, river, Fig. 20.

Urubamba, town, lat. 13° 20′, Fig. 20.

Vilcabamba, river, tributary of Urubamba River entering from
left above Santa Ana, lat. 13°, Fig. 8.
_See also_ Fig. 158.

Vilcabamba, village, lat. 13° 5′, Fig. 20.
_See also_ Fig. 158.

Vilcanota, Cordillera, southern Peru.

Vilcanota, river, name applied to Urubamba above lat. of
Cuzco, 13° 30′, (Fig. 20).

Vilcapampa, Cordillera, lat. 13° 20′, Fig. 20.

Vilque, town, southern Peru, lat. 15° 50′, long. 70° 30′.

Vitor, pampa, lat. 16° 30′, Fig. 66.

Vitor, river, Fig. 66.

Yanahuara, pass, between Urubamba and Yanatili valleys, lat. 13° 10′.

Yanatili, river, tributary of Urubamba entering from right
above Rosalina, (Fig. 20).
_See also_ Fig. 65.

Yavero (Paucartambo), river, tributary of Urubamba entering
from right, lat. 12° 10′, Fig. 8.

Yavero, settlement, at junction of Yavero and Urubamba
rivers, lat. 12° 10′, Fig. 8.

Yunguyo, town, southern Peru, lat. 16° 20′, long. 69° 10′.

Yuyato, river, lat. 12° 5′, Fig. 8.

INDEX

Abancay, 32, 62, 64, 78, 92, 93, 181, 189, 221, 243;
suppressing a revolution, 89-91;
temperature curve (diagr.), opp. p. 180

Abancay basin, 154

Abancay to Camaná cross-section map, work, observation and statistics, 315

Abra Tocate, 73, 80, 81;
topography and vegetation from (ill.), opp. p. 19

Abra de Malaga, 276

Acosta, 205

Adams, G. I., 255

Agriculture, 74-76, 152

Aguardiente, 74. _See_ Brandy

Alcohol, 5, 6

Alluvial fans, 60-63, 70, 270

Alluvial fill, 270-273;
view in Majes Valley (ill.), opp. p. 230

Alpacas, 5, 52

Alto de los Huesos (ill.), opp. p. 7

Amazon basin, Humboldt’s dream of conquest, 33-35;
Indian tribes, 36

Amazonia, 20, 26

Ancachs, 171

Andahuaylas, 89

Andrews, A, C., 295

Angulo, Philippi, 317

Anta, 187, 189, 190

Anta basin, 62, 108, 197;
geology, 250;
view looking north from hill near Anta (ill.), opp. p. 184

Antabamba, 52, 53, 95, 96, 99, 101, 189, 197, 243, 303, 316;
Governor, 95-99, 100-101;
Lieutenant Governor, 96-99, 101;
sketch section, 243

Antabamba Canyon, view across (ill.), opp. p. 106

Antabamba Quadrangle, 316, opp. p. 282 (topog. sheet)

Antabamba region, geologic sketch map and section, 245

Antabamba Valley, 96

“Antis,” 39

Aplao, 106, 115, 116, 181, 226, 231, 255, 256, 257, 273, 318;
composite structure section (diagr.), 259;
temperature curve (diagr.), 181

Aplao Quadrangle (topog. sheet), opp. p. 120

Appendix A, 315

Appendix B, 321

Appendix C, 324

Apurimac, 51, 57, 60, 94, 153, 154;
crossing at Pasaje (ills.), opp. p. 91;
regional diagram of canyoned country, 58

Apurimac Canyon, 189;
cloud belt (ill.), opp. p. 150

Arequipa, 52, 89, 92, 117, 120, 137, 284;
glacial features near (sketches), 280

Argentina, 93

Arica, 130, 132, 198

Arma, 67, 189, 212-214

Arrieros, Pampa de, 280

Asymmetrical peaks (ill.), opp. p. 281

Asymmetry, 305-313;
cross-section of ridge (diagr.), 306;
postglacial volcano (diagr.), 306

Auquibamba, 93

Avalanches, 290

Bailey, S. I., 284

Bandits, 95

Basins, 60, 154;
regional diagram, 61;
climatic cross-section (diagr.), 62

Batholith, Vilcapampa, 215-224

Belaunde brothers, 116

Bergschrunds, 294-305

Bingham, Hiram, ix, 104, 157

Block diagram of physiography of Andes, 186

Boatmen, Indian, 13

Bogotá, Cordillera of, 205

Bolivia, 93, 176, 190, 193, 195, 240, 241, 249, 322;
snowline, 275-277

Bolivian boundary, 68

Border valleys of the Eastern Andes, 68-87

Borneo, 206

Bowman, Isaiah, 8, 316

Brandy, 74, 75, 76, 82-83

Bravo, José, 245

Bumstead, A. H., ix

Cacao, 74, 83

Cacti, 150;
arboreal (ill.), opp. p. 90

Calchaquí Valley, 250

Callao, 118;
cloudiness (with diagr.), 133;
temperature (with diagr.), 126-129;
wind roses (diagrs.), 128

Camaná, 21, 112, 115, 116, 117, 118, 140-141, 147, 181,
225, 226, 227, 266, 318;
coastal Tertiary, 253, 254;
plain of, 229;
temperature curve (diagr.), 181

Camaná Quadrangle (topog. sheet), opp. p. 114

Camaná Valley, 257

Camaná-Vitor region, 117

Camino del Peñon, 110

Camisea, 36

Camp 13, 100, 180, 181;
temperature curve (diagr.), 180

Campas, 37

Canals for bringing water, 59, 60, 155;
projected, Maritime Cordillera (diagr.), 118

Cantas, 115, 116, 226, 253, 257, 273, 318

Canyon walls (ills.), opp. p. 218

Canyoned country, regional diagram, 58;
valley climates (diagr.), 59

Canyons, 60, 72, 73, 197, 219;
Majes River (ill.), opp. p. 230;
topographic conditions before formation of deep
canyons in Maritime Cordillera (ill.), opp. p. 184

Caraveli, climate data, 134-136;
wind roses (diagrs.), 136

Carboniferous fossils, 323

Carboniferous strata, 241-247;
hypothetical distribution of land and sea (diagr.), 246

Cashibos, 37

Catacaos, 119

Cattle tracks (ill.), opp. p. 226

Caucho, 29

Caylloma, 164, 165

Caypi, 316

Central Ranges, asymmetrical peaks (ill.), opp. p. 281;
glacial features with lateral moraines (ill.), opp. p. 269;
glacial topography between Lambrama and Antabamba (ill.), opp. p. 280;
steep cirque walls (ill.), opp. p. 286

Cerro Azul, 118

Cerro de Tunari, 176

Chachani, 280, 284

Chanchamayo, 77

Character. _See_ Human character

Chaupimayu Valley, 77

_Chicha_, 86

Chile, 130, 132, 193, 260

Chili River, 120

Chili Valley, opp. p. 7 (ill.), 117

Chimborazo, 281

Chinche, 271, 272

Chira River, depth diagram, 119, 120

Chirumbia, 12

Choclococha, Lake, 120

Chonta Campas, 37

Choqquequirau, 154

Choquetira, 66, 67, 211;
bowldery fill below, 269;
glacial features, 206-207

Choquetira Valley, moraine, (ill.), opp. p. 208

Chosica, 136, 137;
cloudiness (diagr.), 138

_Chuño_, 57

Chuntaguirus, 41

Chuquibamba, 54, 72, 107, 110, 111, 112, 115, 116, 273, 317-319;
sediments, 258

Chuquibambilla, 53, 189, 220, 221, 222, 236, 243;
alluvial fill (diagr.), 272;
Carboniferous, 244;
fossils, 323

Chuquito pass, crossing (ill.), opp. p. 7;
glacial trough (ill.), opp. p. 205

Cirque walls, steep (ill.), opp. p. 286

Cirques, 294-305;
development (diagr.), 300;
development, further stages (diagr.), 301;
mode of formation (diagr.), 297

Clarke, J. M., 321

Clearing in forest (ill.), opp. p. 25

Climate, coast, 125-147;
eastern border, 147-153;
Inter-Andean valleys, 153-155;
_see also_ Meteorological records

Climatic belts, 121-122;
map, 123

Climatology, 121-156

Cliza, 276

Cloud-banners, 16

Cloud belt, 143, opp, p. 150 (ill.)

Cloudiness, 132;
Callao (with diagr.), 133;
desert station near Caraveli (diagrs.), 137;
Machu Picchu, 160;
Santa Lucia (diagr.), 169

Clouds, Inter-Andean Valley, 155;
Santa Ana (ill.), opp. p. 180;
Santa Lucia, 168;
types on eastern border of Andes (diagrs.), 148;
_see also_ Fog

Coast Range, 111, 113, 114, 116, 118, 225-232;
climate, 122-147;
direction, 267;
diagram to show progressive lowering of saturation
temperature in a desert, 127;
geology, 258;
view between Mollendo and Arequipa in June (ill.), opp. p. 226;
wet and dry seasons (diagrs.), 132

Coastal belt, map of irrigated and irrigable land, 113

Coastal desert, 110-120;
regional diagram of physical relations, 112;
_see also_ Deserts

Coastal planter, 6

Coastal region, topographic and climatic provinces (diagr.), 125

Coastal terraces, 225-232

Coca, 74, 77, 82-83

Coca seed beds (ill.), opp. p. 74

Cochabamba, 93;
temperature (diagrs. of ranges), insert opp. p. 178;
weather data, 176-178

Cochabamba Indians, 276

Colombia, 205

Colorada, Pampa de, 114, 317

Colpani, 72, 215, 216, 222, 223;
from ice to sugar cane (ill.), opp. p. 3

Comanchian fossils, 323

Cómas, 155

Compañia Gomera de Mainique, 29, 31, 32

Concession plan, 29

Conibos, 44

_Contador_, 84-85

Copacavana, 176

Cordilleras, 4, 6, 20, 197

Coribeni, 15

Corn, 57, 59, 62

Coropuna, 109, 110, 112, 202, 253, 317, 319;
elevation, 317;
glaciation, 307;
snowline, 283-285

Coropuna expedition, 104

Coropuna Quadrangle, 197, opp. p. 188 (topog. sheet), 319

Corralpata, 51, 59

Cosos, 231

Cotabambas, 78

Cotahuasi, 4, 5, 52, 54, 60, 97, 101, 103, 104, 180, 197, 199, 316, 317;
alluvial fill, 272;
fossils, 322;
geologic sketch maps and cross-section, 247;
rug weaver (ill.), opp. p. 68;
snowline above, 282-283;
temperature curve (diagr.), 180;
view (ill.), opp. p. 57

Cotahuasi Canyon, 247, 248, 316

Cotahuasi Quadrangle (topog. sheet), opp. p. 192

Cotahuasi Valley, geology, 258

Cotton, 76, 116, 117

Crest lines, asymmetrical, 305-313

Cretaceous formations, 247-251

Cretaceous fossils, 323

Crucero Alto, 188

Cuzco, 8, 10, 21, 52, 62, 63, 92, 102, 107, 193, 197;
railroad to Santa Ana, 69-70;
snow, 276;
view (ill.), opp. p. 66

Cuzco basin, 61, 62, 154, 251;
slopes at outlet (diagr.), 185

Deformations. _See_ Intrusions

Derby, Orville, 322

Desaguadero Valley, 193

Deserts, cloudiness (diagrs.), 137;
rain, 138-140;
sea-breeze in, 132;
tropical forest, 36-37;
wind roses (diagrs.), 136

Diagrams. _See_ Regional diagrams

Dikes, 223

Drunkenness, 103, 105-106, 108

Dry valleys, 114-115

Dunes, 114, 254;
Majes Valley, 262-267;
movement, 132;
superimposed (diagrs.), 265

Duque, Señor, 78

Eastern Andes, 204-224;
regional diagram, 22

Eastern border, climate, 147-153

Eastern valley planter, 3

Eastern valleys, 68-87;
climate cross-section (diagr.), 79

Echarati, 10, 77, 78, 80, 82;
plantation scene (ill.), opp. p. 75

Ecuador volcanoes, 281

Epiphyte (ill.), opp. p. 78

Erdis, E. C., 158

Erosion, 192-195, 210, 211, 305;
_see also_ Glacial erosion; Nivation

Erving, Dr. W. G., 13, 101, 316, 317

_Faena_ Indians, 75, 83-87

Feasts and fairs, 175-176

Ferries, 147

Fig tree (ill.), opp. p. 75

Floods, 151

Fog, 132, 139, 143;
conditions along coast from Camaná to Mollendo, 144-145;
_see also_ Clouds

Forest dweller, 1

Forest Indians. _See_ Machigangas

Forests, clearing (ill.), opp. p. 25;
dense ground cover, trees, epiphytes, and parasites (ill.), opp. p. 155;
moss-draped trees (ill.), opp. p. 24;
mountain, 148-153;
mule trail (ill.), opp. p. 18;
tropical, near Pabellon (ill.), opp. p. 150;
tropical vegetation (ill.), opp. p. 18;
type at Sahuayaco (ill.), opp. p. 90

Fossils, 245, 321;
list of, by geologic periods and localities, 321

Frankland, 278, 309

Frost line, 56-57

Garua, 132

Geographical basis of revolutions and of human character, 88-109

Geologic dates, 195-196;
Majes Valley, 258, 261;
west coast fault, 248-249

Geologic development. _See_ Physiographic and geologic development

Gilbert, G. K., 300, 302, 305

Glacial deposits, 268

Glacial erosion, Central Andes, 305-313;
composite sketch of general conditions, 312;
graphic representation of amount during glacial period, 311

Glacial features, 274-313;
Arequipa (sketches), 280;
Central Ranges; lateral moraines (ill.), opp. p. 269;
eastern slopes of Cordillera Vilcapampa (map), 210

Glacial retreat, 208-214

Glacial sculpture, heart of the Cordillera Vilcapampa (map), 212;
southwestern flank of Cordillera Vilcapampa (map), 207

Glacial topography between Lambrama and Antabamba (ill.), opp. p. 280;
Maritime Cordillera, north of divide on 73d meridian (ill.), opp. p. 281

Glacial trough, view near Chuquito pass (ill.), opp. p. 208

Glaciation, 64, 271;
Sierra Nevada, 305;
Vilcapampa, 204-214;
Western Andes, 202

Glaciers, Panta Mountain (ill.), opp. p. 287;
view (ill.), opp. p. 205

Gomara, 34

Gonzales, Señor, 78

Government, bad, 95

Gran Pajonal, 37

Granite, 215-224;
_see also_ Intrusions

Grass (ill.), opp. p. 154

Gregory, J. W., 205

_Hacendado_, 55, 60

_Haciendas_, 78, 83, 86

Hann, J., 126, 176, 278

Hendriksen, Kai, 98, 315

Hettner, 205

Hevea, 29

Highest habitations in the world, 52, 96;
regional diagram of, 50;
stone hut (ill.), opp. p. 48

Highland shepherd, 4

Highlands, 46

Hobbs, W. H., 286, 287

Horses, 66, opp. p. 91 (ill.)

Huadquiña, 70, 71, 72, 75, 82, 86, 219;
hacienda (ill.), opp. p. 73;
terraces, 272

Huadquirca, 243

Huaipo, Lake, 250, 251

Huallaga basin, 153

Huambo, 243

Huancarama, 64, 87, 189, 243, 303;
view (ill.), opp. p. 106

Huancarqui, 257

Huari, 176

Huascatay, 189, 242, 243;
Carboniferous, 244;
fossils, 322

Huasco basin, 275

Huaynacotas, 103, 316;
terraced valley slope (ill.), opp. p. 56;
terraced valley slopes (ill.), opp. p. 199

Huichihua, 278; alluvial fill (diagr.), 272;
(ill.), opp. p. 67

Human character, geographic basis, 88-109

Humboldt, 33-35, 286

Humboldt Current, 126, 143

Huts, 103;
highest in Peru (ill.), opp. p. 48;
shepherds’, 47, 48, 52, 55

Ica Valley, 120;
irrigated and irrigable land (diagr.), 118

Ice erosion. _See_ Glacial erosion

Incahuasi, 51, 155, 285

Incas, 39, 44, 46, 62, 63, 68, 77, 109, 175

Incharate, 78

Indian boatmen, 13

Indians, as laborers, 26-28, 31-32;
basin type, 63-64;
forest, _see_ Machigangas;
life and tastes, 107-108;
mountain, 46-67, 101-102;
plateau, 40-41, 44-45, 100, 106-109;
troops, 90, 91;
wrongs, 14, 102

Ingomwimbi, 206

Instruments, surveying, 315

Inter-Andean valleys, climate, 153-155

Intermont basin. _See_ Basins

Intrusions, deformations north of Lambrama (diagr.), 243;
deformative effects on limestone strata near Chuquibambilla (diagr.), 221;
lower Urubamba Valley (geologic sketch map), 237;
overthrust folds in detail near Chuquibambilla (diagr.), 222;
principles, 217-219

Intrusions, Vilcapampa, deformative effects near Puquiura (diagr.), 216;
relation of granite to schist near Colpani (with diagr.), 216

Iquique, wind roses (diagrs.), 131

Irrigation, 72, 76, 80, 82;
coastal belt (map), 113;
coastal desert, 119-120;
Ica Valley (diagr.), 118

Islay, Pampa de, 114

Italians, 18, 81

Jaguey, 254, 255, 318

Jesuits, 68

Johnson, W. D., 213, 295, 296, 299, 300

Kenia, Mt., 206, 274

Kerbey, Major, 8, 10

Kibo, 206, 274

Kilimandjaro, 205, 206

Kinibalu, 206

Krüger, Herr, 157

Labor, 26-28, 31-32, 42-43, 74-75, 83-84

La Cumbre Quadrangle, 197, 202, opp. p. 202 (topog. sheet)

La Joya, 132, 133;
cloudiness (diagr.), 134;
temperature curves (diagr.), 134;
wind roses (diagrs.), 135

Lambrama, 90, 92, 285, 316;
camp near (ill.), opp. p. 6

Lambrama Quadrangle (topog. sheet), opp. p. 304

Lambrama Valley, deformation types (diagr.), 243

Land and sea, Carboniferous hypothetical distribution
compared with present (diagr.), 246

Landscape, 183-198

Lanius, P. B., 13

La Paz, 93, 109, 276, 321

La Sama, 12, 13, 40

Las Lomas, 318

Lava flows, 199

Lava plateau, 197, 199, 307-308;
regional diagram of physical conditions, 55;
summit above Cotahuasi (ill.), opp, p. 204

Lavas, volume, 201

Lima, 92, 93, 118, 137, 138;
cloud, 132, 143;
temperature, 126

Limestone, sketch to show deformed, 243

Little, J. P., 135, 157

Llica, 275

Lower Cretaceous fossils, 323

Lower Devonian fossils, 321

Machigangas, 10, 11, 12, 14, 18, 19, 31, 36-45, 81;
ornaments and fabrics (ill.), opp. p. 27;
trading with (ill.), opp. p. 26

Machu Picchu, 72, 220;
weather data (with diagr.), 158-160

Madeira-Mamoré railroad, 33

Madre de Dios, 1, 2, 33

Majes River, 147, 225, 227, 266, 267;
Canyon (ill.), opp. p. 230

Majes Valley, 106, 111, 116, 117, 120, 226, 227, 229-231, 318;
alluvial fill, 273;
date of formation, 258, 261;
desert coast (ill.), opp. p. 110;
dunes, 262-267;
erosion and uplift, 261;
lower and upper sandstones (ill.), opp. p. 250;
sediments, 255;
snowline, 283;
steep walls and alluvial fill (ill.), opp. p. 230;
structural details near Aplao (sketch section), 255;
structural details on south wall near Cantas (sketch section), 257;
structural relations at Aplao (field sketch), 256;
Tertiary deposits, 253-254;
wind, 130;
view below Cantas (ill.), opp. p. 110;
view down canyon (ill.), opp. p. 144

Malaria, 14, 38

Marañon, 41, 59

Marcoy, 79

Marine terrace at Mollendo (ill.), opp. p. 226

Maritime Cordillera, 52, 199-203, 233;
asymmetry of ridges, 308-309;
glacial features, 307;
glacial topography north of divide on 73d meridian (ill.), opp. p. 281;
pre-volcanic topography, 200;
post-glacial volcano, asymmetrical (diagr.), 306;
regional diagrams, 50, 52;
test of explanation of cirques, 303;
volcanoes, tuffs, lava flows (ill.), opp. p. 204;
western border rocks (geologic section), 257;
_see also_ Lava plateau

Matara, 99, 316

Matthes, F. E., 286, 287, 289

Mature slopes, 185-193; between Ollantaytambo and Urubamba
(ill.), opp. p. 185;
dissected, north of Anta (ill.), opp. p. 185

Mawenzi, 206

Meanders, 16, 17

Médanos, 114

Mendoza, Padre, 11

Mer de Glace, 203

Meteorological records, 157-181

Mexican revolutions, 93

Middendorf, 143

Miller, General, 41, 78, 147

Minchin, 241

Misti, El, opp. p. 7 (ill.), 284

Molina, Christoval de, 175

Mollendo, 93, 105, 117;
cloud belt, 143;
cloudiness (diagr.), 134;
coastal terraces, 225;
humidity, 133;
marine terrace (ill.), opp. p. 226;
profile of coastal terraces (diagr.), 227;
temperature curves (diagr.), 134;
wind roses (diagrs.), 129

Mollendo-Arequipa railroad, 117

Mollendo rubber, 32

Montaña, 148, 149, 153

Moquegua, 117;
geologic relations (diagr.), 255

Moraines, 207, 210-211;
Choquetira Valley (ill.), opp. p. 208;
view (ill.), opp. p. 208

Morales, Señor, 11

Morococha, temperature (diagrs. of ranges), insert opp. p. 172;
weather data (with diagrs.), 171-176

Morococha Mining Co., 157, 171

Morro de Arica, 132

Moss, large ground. _See Yareta_

Moss-draped trees (ill.), opp. p. 24

Mountain-side trail (ill.), opp. p. 78

Mountains, tropical, as climate registers, 206

Mulanquiato, 10, 18, 19

Mule trail (ill.), opp. p. 18

Mules, 23, 24, 94, opp. p. 91 (ill.)

Névé, 286-305

Niño, El, 137-138

Nivation, 285-294;
“pocked” surface (ill.), opp. p. 286

Northeastern border, topographic and structural section (diagr.), 241

Occobamba Valley, 79

Ocean currents of adjacent waters, 121-122 (map), 123

Ollantaytambo, 70, 73, 75, 250, 271;
terraced valley floor (ill.), opp. p. 56

d’Orbigny, 322

Oruro, 93

Pabellon, 80, 82, opp. p. 150

Pacasmayo, Carboniferous land plants, 245

Pachitea, 37, 38

Pacific Ocean basin, 248

Paleozoic strata (ill.), opp. p. 198

_Palma carmona_, 29

Palmer, H. S., 250

Paltaybamba, opp. p. 74

Pampacolca, 109

Pampaconas, 69, 211, 213, 215;
rounded slopes near Vilcabamba (ill.), opp. p. 72;
Carboniferous, 244;
fossils, 322;
snow action, 291

Pampaconas River, 316

Pampas, 114, 198;
climate data, 134-136

Pampas, river, 189

Panta, mt., 214;
view, with glacier system (ill.), opp. p. 287

Pará rubber, 32

Pasaje, 51, 57, 59, 60, 236, 238, 240, 241, 243;
Carboniferous, 244;
crossing the Apurimac (ills.), opp. p. 91

Paschinger, 274

Pastures, 141, 187;
Alpine (ill.), opp. p. 58

Paucartambo, 42, 77

Paucartambo River. _See_ Yavero River

Payta, 225

Penck, A., 205

Peonage, 25, 27, 28

Pereira, Señor, 10, 18

Perene, 155

Physiographic and geologic development, 233-273

Physiographic evidence, value, 193-195

Physiographic principles, 217

Physiography, 183-186;
Southern Peru, summary, 197-198

Pichu-Pichu, 284

Piedmont accumulations, 260

Pilcopata, 36

Piñi-piñi, 36

Pisco, 130;
Carboniferous land plants, 247

Piura, 119

Piura River, depth diagram, 119, 120

Piura Valley, 48

Place names, key to, 324

Plantations, 86;
_see also_ Haciendas

Planter, coastal, 6

Planters, valley, 3, 75, 76

Plateau Indians, 40-41, 44-45, 100, 106-109

Plateaus, 196-197

Pleistocene deposits, 267-273

Pomareni, 19

Pongo de Mainique, 8, 9, 11, 15-20, 40, 71, 179, 239, 241, 242, 273;
canoe in rapid above (ill.), opp. p. 11;
Carboniferous, 244;
dugout in rapids below (ill.), opp. p. 2;
fossils, 322;
temperature curve (diagr.), 178;
upper entrance (ill.), opp. p. 10;
vegetation, clearing, and rubber station (ill.), opp. p. 2

Poopó, 195

Potato field (ill.), opp p. 67

Potatoes, 57, 59, 62

Potosí, 249

Precipitation. _See_ Rain

Profiles, composition of slopes and profiles (diagr.), 191

Pucamoco, 78

Pucapacures, 42

Puerto Mainique, 29, 30

Punas, 6, 197

Puquiura, 67, 87, 211, 216, 236, 238, 239, 243, 277;
Carboniferous, 244;
composition of slopes (ill.), opp. p. 198

Puqura, 250

Quebradas, 145, 155

Quechuas, 44, 45, 77, 83

_Quenigo_, 285

Quilca, 105, 117, 226, 266

Quillabamba, opp. p. 74

Quillagua, 260

Railroads, 74, 75, 76, 93, 101-102, 149;
Bolivia, 93;
Cuzco to Santa Ana, 69-70

Raimondi, 77, 78, 109, 110, 135, 155, 170, 316

Rain, 115, 119, 120, 122, 124-125;
coast region seasonal variation, 131-137;
eastern border of Andes, belts (diagrs.), 148;
effect of heavy, 138-140;
effect of sea-breeze, 131-132;
heaviest, 147-148;
Morococha (with diagrs.), 173-176;
periodic variations, 137;
Santa Lucia (with diagrs.), 164-166;
unequal distribution in western Peru, 145-147

Regional diagrams, 50;
index map, 23;
note on, 51

Regions of Peru, 1, 7

Reiss, 205, 208

Revolutions, geographic basis, 88-109

Rhone glacier, 205

Rice, 76

Robledo, L. M., 9, 30, opp. p. 78

Rock belts, outline sketch along 73d meridian, 235

Rocks, Maritime Cordillera, pampas and Coast Range structural
relations (sketch section), 254;
Maritime Cordillera, western border (geologic section), 257;
Moquegua, structural relations (diagr.), 255;
Urubamba Valley, succession (diagr.), 249

Rosalina, 8, 9, 10, 11, 37, 42, 71, 73, 80, 82, 153, 237

Rubber, 18;
price, 32, 33

Rubber forests, 22-35

Rubber gatherers, Italian, 18, 81

Rubber plant (ill.), opp. p. 75

Rubber trees, 152

Rueda, José, 78

Rug weaver (ill.), opp. p. 68

Rumbold, W. R., 321

Russell, I. C., 205

Ruwenzori, 206, 274

Sacramento, Pampa del, 37

Sahuayaco, 77, 78, 80, 83, 179;
forests (ills.), opp. p. 90;
temperature curve (diagr.), 178

Salamanca, 54, 56, 105, 106, 180, 181;
forest, 285;
temperature curve (diagr.), 180;
terraced hill slopes (ill.), opp. p. 58;
view (ill.), opp. p. 107

Salaverry, 119

Salcantay, 64, 72, opp. p. 3 (ill.)

San Geronimo, 276

Sand. _See_ Dunes

“Sandy matico” (ill.), opp. p. 90

San Gabriel, Hacienda, 316

Santa Ana, 69, 72, 78, 79, 80, 82, 93, 153, 179, 237;
clouds (ill.), opp. p. 180;
temperature curve (diagr.), 178

Santa Ana Valley, 10, 82

Santa Lucia, temperature ranges (diagrs.), insert opp. p. 162;
unusual weather conditions, 169-170;
weather data (with diagrs.), 161-171

Santo Anato, 40, 42, 82, 179;
temperature curve (diagr.), 178

Schists and Silurian slates, 236-241

Schrund. _See_ Bergschrunds

Schrundline, 300-305

Schuchert, Chas., 321

Sea and land. _See_ Land and sea

Sea-breeze, 129-132

Shepherd, highland, 4

Shepherds, country of, 46-67

Shirineiri, 36, 38

Sierra Nevada, 305

Sierra Nevada de Santa Marta, 205

Sievers, W., 143, 176, 205, 263

Sihuas, Pampa de, 114, 198

Sillilica, Cordillera, 190, 260

Sillilica Pass, 275

Silurian fossils, 321

Silurian slates, 236-241

Sintulini rapids, 19

Sirialo, 8, 15

Slave raiders, 14

Slavery, 24, 25

Slopes, composition at Puquiura (ill.), opp. p. 198;
composition of slopes and profiles (diagr.), 191;
smooth grassy (ill.), opp. p. 79;
_see also_ Mature slopes

Smallpox, 14, 38

Snow, 212;
drifting, 278;
fields on summit of Cordillera Vilcapampa (ill.), opp. p. 268

Snow erosion. _See_ Nivation

Snow motion, curve of (diagr.), 293;
law of variation, 291

Snowline, 52, 53, 66, 122, 148, 203, 205-206, 274-285;
canting (with diagr.), 279;
determination, 282;
difference in degree of canting (diagr.), 281;
glacial period, 282;
view of canted, Cordillera Vilcapampa (ill.), opp. p. 280

Snowstorm, 170

Soiroccocha, 64, 72, 214;
view (ill.), opp. p. 154

Solimana, 4, 202, 317;
glaciation, 307

Soray, 64

Sotospampa, 243

South Pacific Ocean, 125

Spanish Conquest, 62, 63, 77

Spruce (botanist), 153

Steinmann, 249, 276

Streams, Coast Range, 145-147;
physiography, 192;
_see also_ Water

Structure. _See_ Rocks

Stübel, 209

Sucre, 93

Sugar, 73, 74, 75, 76, 82-83, 92

Sullana, 119

Survey methods employed in topographic sheets, 315

Tablazo de Ica, 198

Tarai. _See_ Urubamba Valley

Tarapacá, Desert of, 260

Tarapoto, 153

Taurisma, 317;
geologic sketch map and cross-section, 248

Taylor, Capt. A., 126, 128

Temperature, Abancay curve (diagr.), opp. p. 180;
Callao (with diagr.), 126-129;
Cochabamba, 176-178;
Cochabamba (diagrs. of ranges), insert opp. p. 178;
curves at various points along 73d meridian, 178-181;
La Joya curves (diagr.), 134;
Mollendo curves (diagr.), 134;
Morococha, 171-173;
Morococha (diagrs. of ranges), insert opp. p. 172;
progressive lowering of saturation, in a desert (diagr.), 127;
Santa Lucia, 161-164;
Santa Lucia (diagrs. of ranges), insert opp. p. 162

Tempests, 169-170

Terraces, coastal, 225-232;
physical history and physiographic development (with diagrs.), 228-230;
profile at Mollendo (diagr.), 227

Terraces, hill slopes (ill.), opp. p. 58

Terraces, marine (ill.), opp. p. 226

Terraces, valley (ills.), opp. p. 56, opp. p. 57, opp. p. 66;
Huaynacotas (ill.), opp. p. 199

_Terral_, 130

Tertiary deposits, 249, 251-267;
coastal, 253

Ticumpinea, 36, 38, 251

Tierra blanca, 254, 266

Timber line, 69, 71, 79, 148

Timpia, 36, 38, 252;
canoe at mouth (ill.), opp. p. 19

Titicaca, 161, 176, 195, 321

Titicaca basin, 107

Titicaca-Poopó basin, 251

Tocate. _See_ Abra Tocate

_Tola_ bush (ill.), opp. p. 6

Tono, 36

Topographic and climatic cross-section (diagr.), opp. p. 144

Topographic and structural section of northeastern border
of Andes (diagr.), 241

Topographic map of the Andes between Abancay and the Pacific
Coast at Camaná, insert opp. p. 312

Topographic profiles across typical valleys (diagrs.), 189

Topographic regions, 121-122;
map, 123

Topographic sheets, survey method employed, 315;
list of, with page references, xi

Topographical outfit, 315

Torontoy, 10, 70, 71, 72, 82, 158, 220

Torontoy Canyon, 272, opp. p. 3 (ill.);
cliff (ill.), opp. p. 10

Trail (mountain-side) (ill.), opp. p. 78

Transportation, 73-74, 93, 152;
rains and, 142

Trees, 150;
_see also_ Forests

_Tucapelle_ (ship), 117

Tucker, H. L., ix

Tumbez, 119

Tunari peaks, 276

Ucayali, 42, 44

Uplift, recent, 190

Upper Carboniferous fossils, 322

Urubamba, 1, 41, 42, 62, 187;
village, 70, 73

Urubamba River, 72;
fossils, 322;
physiographic observations, 252-253;
rapids and canyons, 8-21;
shelter hut (ill.), opp. p. 11

Urubamba Valley, 72, 153, 238;
alluvial fans, 270;
alluvial fill, 272-273;
below Paltaybamba (ill.), opp. p. 74;
canyon walls (ill.), opp. p. 218;
dissected alluvial fans (sketch), 271;
floor from Tarai (ill.), opp. p. 70;
from ice to sugar cane (ill.), opp. p. 3;
geologic sketch map of the lower, 237;
line of unconformity of geologic structure (ill.), opp. p. 250;
rocks, 250;
rocks, succession (diagr.), 249;
sketch map, 9;
slopes and alluvial deposits between Ollantaytambo and Torontoy
(ill.), opp. p. 269;
temperature curves (diagrs.), 178-179;
terraced valley slopes and floor (ill.), opp. p. 66;
vegetation, distribution (ill.), opp. p. 79;
view below Santa Ana (ill.), opp. p. 155;
wheat and bread, 71

Valdivia, Señor, 161

Vallenar, 49

Valley climates in canyoned region (diagr.), 59

Valley planters. _See_ Planters

Valley profiles, abnormal, 305-313

Valleys, eastern;
_see_ Border valleys of the Eastern Andes;
_see also_ Dry valleys, Inter-Andean valleys;
topographic profiles across, typical in Southern Peru (diagrs.), 189

Vegetation, 141;
belts (map), 123;
distribution in Urubamba Valley (ill.), opp. p. 79;
shrubbery, mixed with grass (ill.), opp. p. 154;
Tocate pass (ill.), opp. p. 19;
_see also_ Forests

Vicuña, 54

Vilcabamba, 66;
rounded slopes (ill.), opp. p. 72

Vilcabamba pueblo, 211, 277, 296

Vilcabamba Valley, 189

Vilcanota knot, 276

Vilcanota Valley, alluvial fill, 272

Vilcapampa, Cordillera, 15, 16, 22, 51, 53, 64, 66, 67, 197, 204-224, 233;
batholith and topographic effects, 215-224;
canted snowline (ill.), opp. p. 280;
climatic barrier, 73;
composite geologic section (diagr.), 215;
glacial features, 204-214;
glaciers, 304;
highest pass, crossing (ill.), opp. p. 7;
regional diagram, 65;
regional diagram of the eastern aspect, 68;
schrundline, 302;
snow movement, 287-289;
snow fields on summit (ill.), opp. p. 268;
snow peaks (ill.), opp. p. 72;
snowline, 277, 279;
southwestern aspect (ill.), opp. p. 205;
summit view (ill.), opp. p. 205

Vilcapampa Province, 77

Vilcapampa Valley, bowldery fill, 269

Vilque, 176

Violle, 309

_Virazon_, 130

Vitor, Pampa de, 114, 318

Vitor River, 92, 117, 226, 266, 267

Volcanic country, 199

Volcanic flows, geologic sketch, 244

Volcanoes, glacial erosion, 311;
post-glacial, 306-307;
recessed southern slopes (ill.), opp. p. 287;
snowline, 281;
typical form, 310;
views (ills.), opp. p. 204

Von Boeck, 176

Vulcanism, 199;
_see also_ Volcanoes

Ward, R. De C., 126, 143

Water, 59, 60, 116, 139;
projected canal from Atlantic to Pacific slope of the
Maritime Cordillera (diagr.), 118;
streams of coastal desert, intermittent and perennial,
diagrams of depth, 119

Water skippers, 17

Watkins, Mr., 317, 318

Weather. _See_ Meteorological records

Western Andes, 199-203

Whymper, 205

Wind belts, 122;
map, 123

Wind roses, Callao (diagrs.), 128;
Caraveli (diagrs.), 136;
Iquique (diagrs.), 131;
La Joya (diagrs.), 135;
Machu Picchu (diagrs.), 159;
Mollendo (diagrs.), 129;
Santa Lucia (diagrs.), 167;
summer and winter of 1911-1913 (diagrs.), 130

Winds, 114, 116;
directions at Machu Picchu, 158-159;
geologic action, 262-267;
prevailing, 125;
Santa Lucia (with diagrs.), 166-168;
trade, 122, 124;
sea-breeze, 129-132

Wine, 116, 117

Wolf, 205

Yanahuara pass, 170

Yanatili, 41, 42, 44;
slopes at junction with Urubamba River (ill.), opp. p. 79

_Yareta_ (ill.), opp. p. 6

Yavero, 30, 31, 36, 38, 42, 179;
temperature curve (diagr.), 178

Yavero (Paucartambo) River, rubber station (ill.), opp. p. 24

Yuca, growing (ill.), opp. p. 75

Yunguyo, 176

Yuyato, 36, 38

* * * * *

FOOTNOTES:

[1] For all locations mentioned see maps accompanying the text or
Appendix C.

[2] The Cashibos of the Pachitea are the tribe for whom the Piros
besought Herndon to produce “some great and infectious disease” which
could be carried up the river and let loose amongst them (Herndon,
Exploration of the Valley of the Amazon, Washington. 1854, Vol. 1, p.
196). This would-be artfulness suggests itself as something of a match
against the cunning of the Cashibos whom rumor reports to imitate the
sounds of the forest animals with such skill as to betray into their
hands the hunters of other tribes (see von Tschudi, Travels in Peru
During the Years 1838-1842, translated from the German by Thomasina
Ross, New York, 1849, p. 404).

[3] The early chronicles contain several references to Antisuyu and the
Antis. Garcilaso de la Vega’s description of the Inca conquests in
Antisuyu are well known (Royal Commentaries of the Yncas, Book 4,
Chapters 16 and 17, Hakluyt Soc. Publs., 1st Ser., No. 41, 1869 and Book
7, Chapters 13 and 14, No. 45, 1871). Salcamayhua who also chronicles
these conquests relates a legend concerning the tribute payers of the
eastern valleys. On one occasion, he says, three hundred Antis came
laden with gold from Opatari. Their arrival at Cuzco was coincident with
a killing frost that ruined all the crops of the basin whence the three
hundred fortunates were ordered with their gold to the top of the high
hill of Pachatucsa (Pachatusun) and there buried with it (An Account of
the Antiquities of Peru, Hakluyt Soc. Publs., 1st Ser., No. 48, 1873).

[4] Notice of a Journey to the Northward and also to the Northeastward
of Cuzco. Royal Geog. Soc. Journ., Vol. 6, 1836, pp. 174-186.

[5] Walle states (Le Pérou Economique, Paris, 1907, p. 297) that the
Conibos, a tribe of the Ucayali, make annual _correrias_ or raids during
the months of July, August, and September, that is during the season of
low water. Over seven hundred canoes are said to participate and the
captives secured are sold to rubber exploiters, who, indeed, frequently
aid in the organization of the raids.

[6] Distances are not taken from the map but from the trail.

[7] Compare with Raimondi’s description of Quiches on the left bank of
the Marañon at an elevation of 9,885 feet (3,013 m.): “the few small
springs scarcely suffice for the little patches of alfalfa and other
sowings have to depend on the precarious rains.... Every drop of water
is carefully guarded and from each spring a series of well-like basins
descending in staircase fashion make the most of the scant supply.” (El
Departamento de Ancachs, Lima, 1873.)

[8] Daily Cons. and Trade Report, June 10, 1914, No. 135, and Commerce
Reports, March 20, 1916, No. 66.

[9] Reference to the figures in this chapter will show great variation
in the level of the timber line depending upon insolation as controlled
by slope exposure and upon moisture directly as controlled largely by
exposure to winds. In some places these controls counteract each other;
in other places they promote each other’s effects. The topographic and
climatic cross-sections and regional diagrams elsewhere in this book
also emphasize the patchiness of much of the woodland and scrub, some
noteworthy examples occurring in the chapter on the Eastern Andes. Two
of the most remarkable cases are the patch of woodland at 14,500 feet
(4,420 m.) just under the hanging glacier of Soiroccocha, and the other
the quenigo scrub on the lava plateau above Chuquibamba at 13,000 feet
(3,960 m.). The strong compression of climatic zones in the Urubamba
Valley below Santa Ana brings into sharp contrast the grassy ridge
slopes facing the sun and the forested slopes that have a high
proportion of shade. Fig. 54 represents the general distribution but the
details are far more complicated. See also Figs. 53A and 53B. (See
Coropuna Quadrangle.)

[10] Commenting on the excellence of the cacao of the montaña of the
Urubamba von Tschudi remarked (op. cit., p. 37) that the long land
transport prevented its use in Lima where the product on the market is
that imported from Guayaquil.

[11] The inadequacy of the labor supply was a serious obstacle in the
early days as well as now. In the documents pertaining to the “Obispados
y Audiencia del Cuzco” (Vol. 11, p. 349 of the “Juicio de Limites entre
el Perú y Bolivia, Prueba Peruana presentada al Gobierno de la República
Argentina por Victor M. Maurtua,” Barcelona, 1900) we find the report
that the natives of the curacy of Ollantaytambo who came down from the
hills to Huadquiña to hear mass were detained and compelled to give a
day’s service on the valley plantations under pain of chastisement.

[12] The Spanish occupation of the eastern valleys was early and
extensive. Immediately after the capture of the young Inca Tupac Amaru
and the final subjugation of the province of Vilcapampa colonists
started the cultivation of coca and cane. Development of the main
Urubamba Valley and tributary valleys proceeded at a good rate: so also
did their troubles. Baltasar de Ocampo writing in 1610 (Account of the
Province of Vilcapampa, Hakluyt Soc. Publs., Ser. 2, Vol. 22, 1907, pp.
203-247) relates the occurrence of a general uprising of the negroes
employed on the sugar plantations of the region. But the peace and
prosperity of every place on the eastern frontier was unstable and quite
generally the later eighteenth and earlier nineteenth centuries saw a
retreat of the border of civilization. The native rebellion of the
mid-eighteenth century in the montaña of Chanchamayo caused entire
abandonment of a previously flourishing area. When Raimondi wrote in
1885 (La Montaña de Chanchamayo, Lima, 1885) some of the ancient
hacienda sites were still occupied by savages. In the Paucartambo
valleys, settlement began by the end of the sixteenth century and at the
beginning of the nineteenth before their complete desolation by the
savages they were highly prosperous. Paucartambo town, itself, once
important for its commerce in coca is now in a sadly decadent condition.

[13] Notice of a Journey to the Northward and also to the Eastward of
Cuzco, and among the Chunchos Indians, in July, 1835. Journ. Royal Geog.
Soc., Vol. 6, 1836, pp. 174-186.

[14] Bol. Soc. Geog. de Lima, Vol. 8, 1898, p. 45.

[15] Marcoy who traveled in Peru in the middle of the last century was
greatly impressed by the sympathetic changes of aspect and topography
and vegetation in the eastern valleys. He thus describes a sudden change
of scene in the Occobamba valley: “... the trees had disappeared, the
birds had taken wing, and great sandy spaces, covered with the latest
deposits of the river, alternated with stretches of yellow grass and
masses of rock half-buried in the ground.” (Travels in South America,
translated by Elihu Rich, 2 vols. New York, 1875, Vol. 1, p. 326.)

[16] According to the latest information (August, 1916) of the Bolivia
Railway Co., trains are running from Oruro to Buen Retiro, 35 km. from
Cochabamba. Thence connection with Cochabamba is made by a tram-line
operated by the Electric Light and Power Co. of that city. The Bulletin
of the Pan-American Union for July, 1916, also reports the proposed
introduction of an automobile service for conveyance of freight and
passengers.

[17] During his travels Raimondi collected many instances of the
isolation and conservatism of the plateau Indian: thus there is the
village of Pampacolca near Coropuna, whose inhabitants until recently
carried their idols of clay to the slopes of the great white mountain
and worshiped them there with the ritual of Inca days (El Perú, Lima,
1874, Vol. 1).

[18] Raimondi (op. cit., p. 109) has a characteristic description of the
“Camino del Peñon” in the department of La Libertad: “... the ground
seems to disappear from one’s feet; one is standing on an elevated
balcony looking down more than 6,000 feet to the valley ... the road
which descends the steep scarp is a masterpiece.”

[19] Figs. 67 and 68 are from Bol. de Minas del Perú, 1906, No. 37, pp.
82 and 84 respectively.

[20] The Boletín de Minas del Peru, No. 34, 1905, contains a graphic
representation of the régime of the Rio Chili at Arequipa for the years
1901-1905.

[21] Hann (Handbook of Climatology, translated by R. De C. Ward, New
York, 1903) indicates a contributory cause in the upwelling of cold
water along the coast caused by the steady westerly drift of the
equatorial current.

[22] This is the elevation obtained by the Peruvian Expedition.
Raimondi’s figure (1,832 m.) is higher.

[23] According to Ward’s observations the base of the cloud belt
averages between 2,000 and 3,000 feet above sea level (Climatic Notes
Made During a Voyage Around South America, Journ. of School Geogr., Vol.
2, 1898). On the south Peruvian coast, specifically at Mollendo,
Middendorf found the cloud belt beginning about 1,000 feet and extending
upwards to elevations of 3,000 to 4,000 feet. At Lima the clouds descend
to lower levels (El Clima de Lima, Bol. Soc. Geogr. de Lima, Vol. 15,
1904). In the third edition of his Süd und Mittelamerika (Leipzig and
Vienna, 1914) Sievers says that at Lima in the winter the cloud on the
coast does not exceed an elevation of 450 m. (1,500 feet) while on the
hills it lies at elevations between 300 and 700 m. (1,000 and 2,300
feet).

[24] In most of the coast towns the ford or ferry is an important
institution and the _chimbadores_ or _baleadores_ as they are called are
expert at their trade: they know the régime of the rivers to a nicety.
Several settlements owe their origin to the exigencies of
transportation, permanent and periodic; thus before the development of
its irrigation system Camaná, according to General Miller (Memoirs,
London, 1829, Vol. 2, p. 27), was a hamlet of some 30 people who gained
their livelihood through ferrying freight and passengers across the
Majes River.

[25] A dry pocket in the Huallaga basin between 6° and 7° S. is
described by Spruce (Notes of a Botanist on the Amazon and Andes, 2
vols., London, 1908). Tarapoto at an elevation of 1,500 feet above sea
level, encircled by hills rising 2,000 to 3,000 feet higher, rarely
experiences heavy rain though rain falls frequently on the hills.

[26] Speaking of Cómas situated at the headwaters of a source of the
Perene amidst a multitude of _quebradas_ Raimondi (op. cit., p. 109)
says it “might properly be called the town of the clouds, for there is
not a day during the year, at any rate towards the evening, when the
town is not enveloped in a mist sufficient to hide everything from
view.”

[27] Observer: E. C. Erdis of the 1912 and 1914-15 Expeditions.

[28] Percentages given because the number of observations varies.

[29] Observer: Señor Valdivia. For location of Santa Lucia see Fig. 66.

[30] Observations began on May 12.

[31] For the first half of the month only; no record for the second
half.

[32] Boletín de la Sociedad Geográfica de Lima, Vol. 13, pp. 473-480,
Lima, 1903.

[33] Boletín del Cuerpo de Ingenieros de Minas del Perú, No. 34, Lima,
1905, also reproduced in No. 45, 1906.

[34] The record is copied literally without regard to the absurdity of
the second and third decimal places.

[35] In the Eastern Cordillera, however, snowstorms may be more serious.
Prior to the construction of the Urubamba Valley Road by the Peruvian
government the three main routes to the Santa Ana portion of the valley
proceeded via the passes of Salcantay, Panticalla, and Yanahuara
respectively. Frequently all are completely snow-blocked and fatalities
are by no means unknown. In 1864 for instance nine persons succumbed on
the Yanahuara pass (Raimondi, op. cit., p. 109).

[36] Boletín de la Sociedad Geográfica de Lima, Vol. 27, 1911; Vol. 28,
1912.

[37] Boletín del Cuerpo de Ingenieros de Minas del Perú, No. 65, 1908.

[38] This figure is approximate: some days’ records were missing from
the first three months of the year and the total was estimated on a
proportional basis.

[39] Christoval de Molina, The Fables and Rites of the Yncas, Hakluyt
Soc. Publs., 1st Ser., No. 48, 1873.

[40] See Meteorologische Zeitschrift, Vol. 5, p. 195, 1888. Also cited
by J. Hann in Handbuch der Climatologie, Vol. 2, Stuttgart, 1897; W.
Sievers, Süd und Mittelamerika, Leipzig and Vienna, 1914, p. 334.

[41] The Physiography of the Central Andes, Am. Journ. Sci., Vol. 40,
1909, pp. 197-217 and 373-402.

[42] Results of an Expedition to the Central Andes, Bull. Am. Geog.
Soc., Vol. 46, 1914. Figs. 28 and 29.

[43] The Physiography of the Central Andes, by Isaiah Bowman; Am. Journ.
Sci., Vol. 28, 1909, pp. 197-217 and 373-402. See especially, _ibid._,
Fig. 11, p. 216.

[44] Travels Amongst the Great Andes of the Equator, 1892.

[45] Geografía y Geología del Ecuador, 1892.

[46] Das Hochgebirge der Republik Ecuador, Vol. 2, 2 Ost-Cordillera,
1902, p. 162.

[47] Contributions to the Geology of British East Africa; Pt. 1, The
Glacial Geology of Mount Kenia, Quart. Journ. Geol. Soc., Vol. 50, 1894,
p. 523.

[48] See especially A. Penck (Penck and Brückner), Die Alpen im
Eiszeitalter, 1909, Vol. 1, p. 6, and I. C. Russell, Glaciers of Mount
Rainier, 18th Ann. Rep’t, U. S. Geol. Surv., 1890-97, Sect. 2, pp.
384-385.

[49] Die Sierra Nevada de Santa Marta und die Sierra de Perijá,
Zeitschrift der Gesellschaft für Erdkunde zu Berlin, Vol. 23, 1888, pp.
1-158.

[50] For a list of the fossils that form the basis of the age
determinations in this chapter see Appendix B.

[51] Eastern Bolivia and the Gran Chaco, Proc. Royal Geogr. Soc., Vol.
3, 1881, pp. 401-420.

[52] The Physiography of the Central Andes, Am. Journ. Sci., Vol. 28,
1909, p. 395.

[53] See paper by H. S. Palmer, my assistant on the Expedition to the
Central Andes, 1913, entitled: Geological Notes on the Andes of
Northwestern Argentina, Am. Journ. Sci., Vol. 38, 1914, pp. 309-330.

[54] The best photograph of this condition which I have yet seen is in
W. Sievers, Südund Mittelamerika, second ed., 1914, Plate 15, p. 358.

[55] Paschinger, Die Schneegrenze in verschiedenen Klimaten. Peter.
Mitt. Erganz’heft, Nr. 173. 1912, pp. 92-93.

[56] Hann, Handbook of Climatology, Part 1, trans. by Ward, 1903, p.
232.

[57] S. I. Bailey, Peruvian Meteorology, 1888-1890. Ann. Astron. Observ.
of Harvard Coll., Vol. 39, Pt. I, 1899, pp. 1-3.

[58] F. E. Matthes, Glacial Sculpture of the Bighorn Mountains, Wyoming,
Twentieth Ann. Rept. U. S. Geol. Surv., 1899-1900, Pt. 2, p. 181.

[59] Idem, p. 190.

[60] W. H. Hobbs, Characteristics of Existing Glaciers, 1911, p. 22.

[61] Op. cit., p. 286. Reference on p. 190.

[62] Corrosion of Gravity Streams with Application of the Ice Flood
Hypothesis, Journ. and Proc. of the Royal Society of N. S. Wales, Vol.
43, 1909, p. 286.

[63] G. K. Gilbert, Systematic Asymmetry of Crest Lines in the High
Sierra of California. Jour. Geol., Vol. 12, 1904, p. 582.

[64] Op. cit., p. 300; reference on p. 582.

[65] Op. cit., p. 300; see pp. 579-588 and Fig. 8.

[66] The observation at Camaná checks very closely with a Peruvian
observation the value of which is S. 16° 37′ 00″.

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