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Title: Remarks on a Pamphlet Lately published by the Rev. Mr. Maskelyne, Under the Authority of the Board of Longitude
Author: Harrison, John
Language: English
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*** Start of this Doctrine Publishing Corporation Digital Book "Remarks on a Pamphlet Lately published by the Rev. Mr. Maskelyne, Under the Authority of the Board of Longitude" ***

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                                 ON A

                        Lately published by the
                         Rev. Mr. _MASKELYNE_,

                      Under the AUTHORITY of the
                          BOARD OF LONGITUDE.

                           By JOHN HARRISON.

                          THE SECOND EDITION.

                 Printed for W. SANDBY in Fleetstreet.

                           (PRICE SIXPENCE.)


A Publication having lately been made by the Rev. Mr. _Maskelyne_
Astronomer Royal, under the Authority of the Board of Longitude,
manifestly tending, by the Suppression of some Facts and the
Misrepresentation of others, to impress the World with an unjust Opinion
of my Invention, and falsely asserting that my Watch did not at certain
Periods therein mentioned keep Time with sufficient Exactness to
determine the Longitude within the Limits prescribed by the Act of the
12th of Queen _Anne_; I think it incumbent upon me to submit some
Observations thereon to the impartial Publick; and the rather, because
the said Pamphlet is rendered so confused by unnecessary Repetitions,
and voluminous Tables, that a Man must be pretty conversant in these
Matters, to trace and combine the Facts, so as to check the
Conclusions, which would consequently be taken upon Trust by the
generality of Readers, unless publickly contradicted. As it will be my
Endeavour so far to avoid the Use of all Terms of Art as to make the
Subject generally intelligible, I flatter myself I shall not be thought
impertinent for giving a short Explanation (though quite unnecessary to
the far greater Part of my Readers) of what the Longitude is, and what
the Service required of the Watch.

The Longitude of any Place is its Distance East or West from any other
given Place; and what we want is a Method of finding out at Sea, how far
we are got to the Eastward or Westward of the place we sailed from. The
Application of a Time-Keeper to this Discovery is founded upon the
following Principles: The Earth’s Surface is divided into 360 equal
Parts (by imaginary Lines drawn from North to South) which are called
Degrees of Longitude; and it’s daily Revolution Eastward round it’s own
Axis is performed in 24 Hours; consequently in that Period, each of
those imaginary Lines or Degrees, becomes successively opposite to the
Sun (which makes the Noon or precise Middle of the Day at each of those
Degrees); and it must follow, that from the Time any one of those Lines
passes the Sun, till the next passes, must be just four Minutes, for 24
Hours being divided by 360 will give that Quantity; so that for every
Degree of Longitude we sail Westward, it will be Noon with us four
Minutes the later, and for every Degree Eastward four Minutes the
sooner, and so in Proportion for any greater or less Quantity. Now, the
exact Time of the Day at the Place where we are, can be ascertained by
well known and easy Observations of the Sun if visible for a few Minutes
at any Time from his being ten Degrees high ’till within an Hour of
Noon, or from an Hour after Noon ’till he is only 10 Degrees high in the
Afternoon; if therefore, at any Time when such Observation is made, a
Time-Keeper tells us at the same Moment what o’Clock it is at the Place
we sailed from, our Longitude is clearly discovered. To do this, it is
not necessary that a Watch should perform it’s Revolutions precisely in
that Space of time which the Earth takes to perform her’s; it is only
required that it should invariably perform it in _some known Time_, and
then the constant Difference between the Length of the one Revolution
and the other, will appear as so much daily gained or lost by the Watch,
which constant Gain or Loss, is called _the Rate of its going_, and
which being added to or deducted from the Time shewn by the Watch, will
give the true Time, and consequently the Difference of Longitude.

I shall now proceed to make such Remarks as occur to me on Perusal of
Mr. _Maskelyne_’s Pamphlet.

Mr. _Maskelyne_ begins by telling us that the Board of Longitude, at
their Meeting, _April_ 26, 1766, came to a Resolution that my Watch
should be tried at the Royal Observatory under his Inspection, and that
he accordingly received it on the 5th of _May_, 1766. He then says, “I
most Days wound up and compared the Watch with the transit Clock of the
Royal Observatory myself; at other times it was performed by my
Assistant _Joseph Dymond_, and afterwards _William Baily_; this was
always done in the Presence of, and attested by one of the Officers of
_Greenwich_ Hospital, when he came to assist in unlocking the Box in
which the Watch is kept, in order to its being wound up.”

Not one of those Attestations appears in the Book: Perhaps Mr.
_Maskelyne_ thinks his Assertion of the Fact will be sufficient for the
Publick, and indeed so it might have been to me, had I not received
different Information: But the Truth is, the Commissioners appointed a
Set of Gentlemen to attend by Rotation the winding up of the Watch; they
were to unlock the Box the Watch was in, to see it wound up and compared
with the Clock, then to lock the Box again and take the Key with them,
and Mr. _Maskelyne_ was to have another Key, there being two Locks to
the Box:[1] The Officers of _Greenwich_ Hospital were appointed for
this Service, some of whom from the Infirmities of Age, and Misfortunes
in the Service, were scarce able to get up the Hill to the Observatory,
so that when they came there, as can be proved from undoubted Eye
Witnesses, they only unlocked the Box, sate down ’till Mr. _Maskelyne_
had done what he thought proper, and then locked the Box again, and
departed: and whatever Attestation they may be supposed to have made, I
can prove that at several Times when Gentlemen of my Acquaintance
happened to be present, the Attendance of the Officers was by no Means
an effectual Check upon the Comparison of the Watch with the Clock. I
would not be thought to accuse those Gentlemen of Neglect of the Duty
imposed upon them; on the contrary I applaud their Diligence in being
ready at all Hours of the Day to attend when Mr. _Maskelyne_ was pleased
to appoint; and therefore I will even for the present (though contrary
to Fact) suppose they have been the Check proposed by the Commissioners
of Longitude against any unfair Access _to the Watch_, still _the Clock_
with which it was compared _was left entirely in_ Mr. Maskelyne_’s
Power_, and an Alteration of the one could not but produce just the same
Effect as an Error of the other, nor is there even the least _Pretence
of a Check_ either on the Clock, or on its Comparison with Observations
of the Sun; nay on the contrary, Mr. _Maskelyne_ did at this Time take
the Key of the Clock from Mr. _Dymond_ in whose Custody it used to be,
and kept it himself.

Mr. _Maskelyne_ then proceeds to give us an Account of the Watch’s
going from Day to Day, which in his 15th Page he concludes thus: “From
the foregoing Numbers it appears, that the Watch was getting from the
very first near 20 seconds per day; a circumstance which is not my
business to account for; but which, as it kept near mean Time in the
Voyage to Barbadoes, seems to shew that the Watch cannot be taken to
pieces and put together again without altering its Rate of going
considerably, contrary to Mr. _Harrison_’s Assertions formerly.”

When I made the Discovery, upon Oath, of the Principles and Construction
of the Watch, to six Gentlemen appointed by the Board of Longitude and
to Mr. _Maskelyne_, (who insisted on having a Right to attend, as being
a Commissioner) which Discovery was finished on the 22d Day of _August_,
1765, as appears by the annex’d Certificate,[2] the Watch then remained
in my Hands, all taken to pieces: I little imagined the Board of
Longitude would take it from me, as not conceiving any Use they could
make of it; and having besides received Assurances from them, that they
only wanted the formal Delivery of it, in compliance with the Terms of
the new Law, without meaning to deprive me of the Use of it: I therefore
went on making some experiments, and alter’d the Rate of its going,
thereby to determine a Fact I wanted to be satisfied about. The Watch
was under this Experiment the latter End of _October_, 1765, when upon
receiving the Certificate for the Remainder of the first Moiety of my
Reward, I was ordered to deliver it to the Board. My Son, attending with
it, being asked if it was then as fit as before to ascertain the
Longitude, reply’d in the Affirmative; for as I have before shewn, the
_Rate of its going_, when once ascertained, does not prevent its keeping
the Longitude. He was not asked the present Rate of its going, nor could
he have answer’d with precision if he had, because we had not had Notice
sufficient to determine that Point; but we did, at that Time, tell
several of our Friends that it went about 18 or 19 Seconds a Day,
_fast_, and we have at several Times since (without ever dreaming that
this was to become a Point of public Discussion) had Occasion to mention
the same Thing to several Members of Parliament, Commissioners of
Longitude and other Gentlemen, insomuch that we did not believe any body
was uninformed of it, who at all attended to the Business of the

This may serve to account for the Circumstance which Mr. _Maskelyne_
declares, _it was none of his Business to account for_, why the Watch
was getting near 20 Seconds per Day; but as to _his Inference_, I must
say it betrays the most absolute Ignorance of Mechanics, and of this
Machine in particular, in which it is obvious (and for this Fact I
appeal to the Watchmakers who saw it taken to Pieces) that its going at
the same Rate when put together again, as before, depends (if none of
the Parts are alter’d) upon nothing more complicated _than putting a
single Screw into the same Place from whence it was taken_. Indeed this
Passage, and the ignorant and puerile Remarks which Mr. _Maskelyne_ has
been suffer’d to prefix to my written Description of the Watch (to the
Disgrace of this Country in those foreign Translations it has already
undergone) bring strongly to my Remembrance an Observation made by some
of the Gentlemen present at the Discovery, “that they wonder’d at his
Patience in attending so long to a Subject he seem’d so totally
unacquainted with.”

Mr. _Maskelyne_ then proceeds to tell us of a Change that happen’d in
the going of the Watch, and says, “this Change began in the Beginning of
_August_, on the few and only hot Days we had last Summer, which yet
were not extreme, the Thermometer within Doors having never risen above
73°. The Rest of the Summer in general was remarkably cool and
temperate.” When I took this Watch to Pieces I informed Mr. _Maskelyne_
and the other Gentlemen, that in trying any Experiments with it, in
Respect to Heat and Cold, it would be proper that it should be so fixed
that, as far as could be, the Heat should have an equal Influence on all
Sides of it; and it is obvious that the Thermometer ought to have been
kept in the same Box with it; but as this was not done, I apprehend the
Effects of Heat mention’d above do not merit much Attention; and
therefore shall only observe that the Watch was placed in a Box with a
Glass in the Lid and another in one Side, in the Seat of a Window level
with the lowest Pane of the Window, and exposed to the South East,
whilst the Thermometer, which was to ascertain the Degree of Heat the
Watch was exposed to, was placed in a shady Part of the Room: Now ’tis
obvious that while the Air surrounding the Thermometer might be very
temperate, there might, if the Sun shone upon it, be a heat in the Box,
superior to what was ever felt in the open Air in any Part of the World;
and perhaps greater than any human being could subsist in, and
consequently improper, or at least unnecessary for this experiment.

Mr. _Maskelyne_ next tells us of an irregularity which he says happened
in cold Weather, and says, “However, it seems in general that the Frost
must have been the cause of these irregularities, as well as of the
Watch’s going so much slower in the Month of _January_, than it had gone
before.” Mr. _Maskelyne_ ought along with this, to have published what I
told him when I explained it; that the Provision against the effects of
Heat and Cold was not _in this Machine_ extended to all Degrees; that I
never had tryed it so low as the freezing Point, which according to the
best Informations I have been able to procure is a Degree of Cold _that
never did exist between the Decks of a Ship at Sea_, in any Climate yet
explored by Mankind.

Mr. _Maskelyne_ then comes to the Rate of its going in different
Positions; and says, “It is obvious, these last-mentioned Trials of the
Watch in a vertical Position could not be designed to shew how near it
would go at Sea, where it can never obtain these Positions: the Intent
of them is to prove how near Mr. _Harrison_’s Execution of his Watch
comes up to his Principles, with respect to the making all the Arcs
described by the balance, whether large or small, to be performed in the
same Time, as Mr. _Harrison_ asserts them to be.” Mr. _Maskelyne_ here
also might have had Candour enough to inform the Public, as I did him,
that although the Watch was quite sufficient to answer the Purposes
required of it in Navigation, and to fulfil what was prescribed by the
Act of Queen _Anne_, yet it was far from being in a state of Perfection,
_as an universal exact Time-Keeper for every Purpose_: I shew’d him and
the rest of the Gentlemen the Reasons why the Machine then before them,
would not go at the same Rate in such different Positions _into which
the Motion of a Ship could never put it_; and whilst I explained to them
those Imperfections in the particular Machine we were examining, I also
in the clearest Manner I was able, pointed out the means of remedying
them with certainty in others, which the Gentlemen skill’d in Mechanics
seem’d perfectly to comprehend, and to be satisfied of the Truth which I
again assert, that Watches made on my Principles will endure a much
greater Motion and change of Position than they can ever be subject to
in a Ship; and that they will not be affected by any Degree of Heat or
Cold, in which a Man can live.

If any Thing was meant to be concluded with respect to me by this
Experiment, either in Point of Property or of Reputation, common Justice
would have required that I should have had an Opportunity of seeing the
Facts ascertained; and when such a Trial was directed as put the Result
in the absolute Power of a single Person, that I should have been
satisfied of his Integrity, Disinterestedness and Ability for the
purpose. I would not be understood to attack Mr. _Maskelyne_’s Knowledge
of the Theory of Astronomy; as for any Thing I know to the contrary, it
may be of the very first Rate, especially as the Commissioners have
thought proper to entrust him with the Execution of their commands; and
which he has ever been as ready to undertake: But alas! as to his skill
in Mechanics, he knows little or nothing of the matter he has ventur’d
to take in Hand.

I think it more consistent with the respect I owe to the Public, and
myself, to speak out plainly, than to have recourse to _Insinuations_,
on a Subject of this nature: I therefore declare, that I am not
satisfied with the Truth of his reporting other Observations relative to
the Longitude, as I do maintain that in both his Voyages the
Observations which he said he made the Land by, were not calculated till
after he had seen the Land; and I am certain those he has given, in the
Publication now before us, are not genuine, for he pretends to find each
Observation of the Transit of the Sun to the hundredth part of a Second
of Time,—a Degree of exactness about twenty Times beyond what any other
Observer has hitherto found practicable: Moreover I know him to be
deeply interested in the Lunar Tables, a Scheme set up some Years ago
for the Reward in Competition with my Invention, and for which large
Sums of Money have already been paid by the Public.

Although I flatter myself the Reader is already in Possession of very
sufficient Reasons for rejecting the whole Pamphlet as partial and
inconclusive, yet I entreat his patient Attention whilst I advance one
step farther, and shew, that although Mr. _Maskelyne_ has presented us
with a set of Observations which _according to his mode of Calculation_,
prove what he advances, yet those very Observations when rightly
reasoned upon _prove the contrary_; and that in each of the Periods he
refers to, except those of the severe Frost and improper Positions
(against which Mr. _Maskelyne_ ought to have informed the World I never
warranted this particular Watch) it kept Time with sufficient
correctness to determine the Longitude within the limits of the Act of
Queen _Anne_.

The Reader by this Time knows enough of the Subject to see, that in
order to try whether the Watch would or would not keep Time with
sufficient Exactness to determine the Longitude, Mr. _Maskelyne_’s first
Operation, after receiving it, should have been to ascertain _the Rate
of its going_. But no such Thing happened: he knew it had not gone
exactly correspondent to mean Time, during the Voyage to _Barbadoes_; it
had been publickly enough declared that its Rate of going had been since
altered; and, if he had not received that Information, he might nay must
have discovered it in the first 24 Hours Tryal; however, without once
attending to this _essential Circumstance_, he goes to work, comparing
the first Period of six Weeks (which he observes is generally reckoned
the Term of a West-India Voyage) when it was in an horizontal Position,
with _mean Time_, instead of _the corrected Time_, and each succeeding
Period with that immediately preceeding it! Who can hesitate in
pronouncing that his Conclusions must be all erroneous? He should first
have ascertained the Rate of its going by a Length of Observations of
the Sun or Stars, or by a perfect Pendulum Clock if he had such a one,
and then have corrected the Time shewn by the Watch accordingly.
However, supposing for a Moment his _Facts_ to be genuine, I will deduce
the _real Result_ in the best Manner the Observations will admit,
rejecting those made while the Watch was in improper Positions, and
those during the Frost, for the same Reasons that Mr. _Maskelyne_ lays
no Stress upon them, and for those I have already stated. I shall
therefore (pursuing his Idea of six Weeks) take it during the first
tranquil six Weeks that it had, viz. from _July_ the 6th, to _August_
the 17th, in which Time it gained in all 11 Minutes, 50 Seconds, or
16-9/10 Seconds per Day which I will assume as the Rate of its going, or
if Mr. _Maskelyne_ pleases I will take the Average of his whole Time of
Examination, from the 6th of _July_ to the 3d of _January_ and from the
9th of _January_ to the 4th of _March_, which will come out at the Rate
of 16-8/10 Seconds per Day fast, and I say that according to either of
those Rates of going, the Watch kept the Longitude within the Limits of
the Act of Queen _Anne_, during any Period of six Weeks that can be
pointed out, excepting those of extreme Cold, and improper Position
which have already been explained. I do not trouble the Reader with the
Calculations: If I assert an Untruth, I shall hardly escape

There is another Inaccuracy, which tho’ of less Consequence, ought not
to escape notice. One would naturally suppose when Mr. _Maskelyne_ found
the Watch went at this Rate of gaining on Mean Time, he would have been
very exact in his Time of comparing it with his Clock; but on the
contrary we find he was so irregular as to vary his Comparisons on
succeeding Days from half an Hour to four Hours and 48 Minutes, and this
not for a Time or two, but for one third of the whole Time he had it.

Mr. _Maskelyne_ having shewn from the Result of his Calculation (which I
have here proved to be false) that the Watch is not to be depended upon
to determine the Longitude in a Voyage of six Weeks, then says, “these
Considerations are sufficient to explain the Motives which might have
actuated Mr. _Harrison_, as a Man of Prudence, in desiring to send his
Watch two Voyages to the West Indies, upon his Idea that he should be
intitled to the large Rewards prescribed in the Act of the 12th of Queen
_Anne_, in Case his Watch kept Time within the Limits there mentioned,
whether the Method itself was or could be rendered generally useful and
practicable, or not;” this Insinuation _(published under the Authority
of the Commissioners of Longitude)_ that I had contrived a Trial which I
knew the Watch would fulfil, whilst I was conscious that it would not
answer the general Purposes of the Act of Queen _Anne_, and consequently
that I had formed a villainous Scheme to rob the Publick of the Reward
without really and effectually performing the Conditions, strikes me as
a Charge of so atrocious a Nature, that I think myself not only
_justified_ in publishing to the World what has been done with respect
to Trials of the Merit of my Invention, but even _indispensably obliged_
so to do. I well know what I hazard thereby, and if the rest of my
Reward cannot be obtained on Principles of _National Faith_ and _Publick
Spirit_, I am contented to forego it, but I will not descend into the
Grave loaded with that Dishonour which my Enemies, availing themselves
of their Rank or Offices, have, in various Ways, attempted to throw upon

In the first Place I must remark, that the Trial referred to was not
fixed _by me_, but by _an Act of Parliament_ passed so long ago as the
Year 1714, which (after vesting certain discretionary Powers in
Commissioners to judge what Methods are likely to prove practicable, and
authorizing them to issue smaller Sums of Money) goes on to fix the last
grand Test of the Merit of any such Invention, and enacts “that when a
Ship, under the Appointment of the said Commissioners, shall thereby
actually sail from _Great Britain_ to the _West Indies_ without losing
her Longitude beyond certain Limits, the Inventor shall be intitled to
certain Rewards.” Having from the Year 1726, employed myself in
adapting those Principles which I had _at that Time_ executed in a
Pendulum Clock, to an Instrument or Time-Keeper so constructed as to
endure the Motion of a Ship at Sea, and having made a Voyage to _Lisbon_
and done sundry other Things during a Course of Years, mostly under the
Direction of the Commissioners of Longitude, by way of preparatory
Experiments, I thought the Invention sufficiently perfect about the
latter End of the Year 1760, to go upon the ultimate Trial, which I
accordingly applied for. My Son, after being sent to _Portsmouth_ with
the third Time-keeper (the fourth or Watch being to be sent to him) was
kept there five Months, waiting for Orders; which having by returning to
_London_ at Length obtained, he went to _Jamaica_ in the _Deptford_ Man
of War, and returned in the _Merlin_ Sloop of War, having fulfilled
every Instruction of the Commissioners. It remained to compute from the
Astronomical Observations made at _Portsmouth_ and _Jamaica_, whether
the Watch had or had not kept the Longitude within the prescribed
Limits; and as my Title to 20,000_l._ was to be determined thereby, I
thought it but reasonable that I should name some Person to check the
Computations, _which was refused_. The Commissioners appointed three
Gentlemen for that Purpose, and on receiving their Report were pleased
to declare _that the Watch had not kept its Longitude within the above
mentioned Limits_.[3] Thoroughly convinced of the contrary (for I had
the same Materials they had to calculate from) I required a Copy of the
Computations _which was also refused me_; nor could I ever obtain a
Sight of them either officially or through private Favour, ’till three
Years afterwards, when they were ordered to be laid before the House of
Commons; and it then appeared that two of the three Computations were
absolutely inconclusive, proving nothing, and the third decided in my
Favour. Further Proof of the Watch having succeeded in this Voyage may
be found in the Journals of the House of Commons, Vol. XXIX. P. 546, in
the Evidence of _George Lewis Scott_ Esq; and Mr. _James Short_.

The Reader will easily believe I did not feel perfectly easy under this
Treatment of an Invention to the perfecting of which (encouraged by the
long continued Patronage of a _Graham_, a _Halley_, a _Folkes_, &c.
&c.——learned Friends to Society, and Publick Good, whose Minds were
too enlarged, and Spirits too liberal to admit that _little_ Jealousy of
inferior Artists, which since their Death I have been exposed to) I
gloried in sacrificing every Prospect of Advantage from other Pursuits,
and had willingly submitted to lead a Life of Labour and Dependence.
However ’twas too late to retreat; and I had only one Means of Success
left which was to follow the Commissioners in their own Way. Accordingly
after many Difficulties (with a Relation of which I will not tire the
Reader, as it is by no Means my Intention to meddle with any Subjects of
Complaint, except such as are material to the forming a right Judgment
of the Trials made and proposed) a second Voyage to the _West Indies_
was agreed to in the latter End of the Year 1762, which Agreement was
afterwards well nigh overset by the Commissioners insisting on such
Astronomical Observations being previously made, as were next to
impracticable in this Climate, and could be put into the Instructions
for no other Reason that I could conceive, but to throw insuperable
Difficulties in my Way, as they were not at all material to the
Determination of the Matter in Question. However the Commissioners at
Length gave up this Point on my Opinion of the Impracticability being
confirmed by that of an Officer of the Navy distinguished for his
Abilities and Skill in Matters of Astronomy. To take away all
Possibility (as I thought) of this Voyage being rendered fruitless like
the last, I then desired to have inserted at the End of the Instructions
some few Words to this Purpose, “that provided the Experiment answered,
the Commissioners present were of Opinion I should _without further
Trouble_ receive my Reward;” but my Son attending the Board with this
Proposition was told by Lord _Sandwich_ at that Time President, that it
would be mere Tautology, for that their giving Instructions implyed the
same Thing, and that if the Watch kept its Time within the Limits of the
Act there could be no Doubt of my being entitled to and receiving the
Reward, and nobody could take if from me. Upon the Faith of this, my Son
went the Voyage to _Barbadoes_, in which the Watch kept its Time
“considerably within the nearest Limits of the Act of Queen _Anne_,” as
certified, even by the Commissioners themselves.

On the Success of this Trial being known, and after having employed near
forty Years of my Life on the Faith of an Act of Parliament, was a
Doctrine broached to me (as I solemnly declare _for the first Time_)
that the Commissioners were invested with a discretionary Power of
ordering other Trials and the fulfilling of other Conditions than those
specially annexed by Act of Parliament to the Reward;[4] An Exposition
of the Law, which I ever did and ever shall (until it is supported by
legal Authority) totally reject and refuse Obedience to; for I do
maintain, that before passing the last Act of Parliament I had as full
and perfect a _Right_ to the Reward of 20,000_l._ as any Free-holder in
_Britain_ has to his Estate; and I never would have desired nor ever
will desire any better Satisfaction than a judicial Determination of
that Point; which however it was very soon thought proper to preclude me
from, by a new Law, passed at the Instance of the Commissioners of
Longitude, placing me _too certainly_ under the Discretion of the
Commissioners and totally changing the Terms on which the Reward was to
be given me, enacting that I should have half of it when I had disclosed
the Principles and Construction of the Machine, and assigned over for
the Use of the Publick the last made Timekeeper, together with the three
others which were not so perfect as the last; and the other half when I
should have made more Watches, _without determining how many_, and
proved them to the Satisfaction of the Commissioners, _without defining
the Mode of Trial_.

I frankly confess that from thenceforward I considered the second Moiety
of the Reward as lost for ever. The first Moiety I obtained, tho’ it was
with great Difficulty, as the Act required me to explain my Invention
upon Oath, and the Commissioners were pleased to put into that Oath,
Words of an indeterminate and unlimited Meaning, and refused to explain
them, or even permit me or my Son to ask what was meant by them. We at
length agreed to take it (finding we should never get any Thing if we
did not, such was now the Power of the Commissioners) and they declared
that themselves and the Gentlemen appointed by them to whom we were to
explain it, would be _upon Honour_ not to disclose it, that I might have
an Opportunity of obtaining the Reward promised by foreign Powers;
however, in less than a Month an Account of it appeared in the public
News-Papers, signed by the Rev. Mr. _Ludlam_, one of the six Gentlemen
named by the Commissioners to receive the Discovery, and therefore, I
make no doubt, by Leave of the Board. Nor did they stop here, for they
have since published all my Drawings without giving me the last Moiety
of the Reward, or even paying me and my Son for our Time at the Rate of
common Mechanicks; a Discouragement to the Improvement of Arts and
Sciences, and an Instance of such Cruelty and Injustice as I believe
never existed in a learned and civilized Nation before.

I have already had Occasion to mention, that at the Time I receiv’d the
Certificate for the first Moiety of the Reward, the Watch was delivered
up; it remained six Months locked up at the Admiralty, and was then
removed to Greenwich, to be the Subject of those Experiments concerning
which I now trouble the Public. The other three Machines, were (by Order
of the Commissioners) soon after demanded of me by Mr. _Maskelyne_. One
of them which had been going more than thirty Years, was broke to Pieces
_under his careful and ingenious management_, before it got out of my
House; and the other two were so far abused in the Carriage by Land to
_Greenwich_, as to be rendered quite incorrect, and as far as I can
learn, incapable of being repaired without having some essential Parts
made anew: Thus perished the first Essays of this long-wished for

Unwilling however that the Public should lose the Benefit of the
Discovery, or the Chance of further Improvement, I applied, by repeated
Letters, to the Board, praying that the Watch might be lent to me
(offering Security for it if required) for the Sake of employing other
Workmen to make the different Parts by Model, with quicker Dispatch, and
in Order to determine by Experiments, whether some expensive Parts of
the Machinery might not be abridged or totally left out. Still have my
Requests been refused, and of late they have alledged that they cannot
keep their Engagements with Mr. _Kendall_ if they were to lend me the
Watch. What those Engagements are may be seen below.[5] The new Act, as
I have already observ’d, did not determine _how many_ more Watches were
to be made before I should receive the other Moiety of the Reward: it
was seven Months before I could get them to fix _how many_, and then
they would neither agree to any Mode of Trial proposed by me, nor
propose any themselves till _eleven Months_ after that, _viz._ not till
the 11th Day of _April_ last, when (an Enquiry having been set on Foot
in the House of Commons) they were pleased to propose, that instead of
the Length of a _West-India_ Voyage, which is about _six Weeks_, the
Watches should be placed with their very good Friend and Well-wisher Mr.
_Maskelyne_ for _ten months_, and then be sent for two months on board a
Ship in the _Downs_; and all this I am required to submit to, without
the least Shadow of Assurance on their Part, that they will be satisfied
with this Trial, let it answer ever so well, or that I shall thereby be
brought at all the nearer receiving what is due to me, altho’
(independent of making the Watches) it must necessarily employ one whole
Year of mine or my Son’s Time, in superintending an Examination, which,
after all, can only prove that I, who have made one Machine, can make
another like it; and the Point of general Practicability, about which so
much stir is _affected_ to be made, would not be one Jot advanced beyond
what it is at present.

I cannot help begging the Reader will here allow me to add a Remark or
two upon the general Practicability of my Invention, as that is now
said to be the only Thing that was in Dispute between the Commissioners
and me, and that they only wanted to be satisfied as to this Point. In
order to clear it up then, I will submit to the Public to determine
whether the general Use and Practicability of my Invention can, in the
Nature of Things, be attacked, unless under one of these three following

1. That a Time-keeper, however perfect, is an insufficient Means of
ascertaining the Longitude at Sea.

2. That such Information has not been given as will enable other Workmen
to make other Time-keepers of equal goodness with that which is
certified to have kept the Longitude.

Or 3. That they will come to so enormous a Price as to be out of the
Reach of Purchase.

From the Benefit of the first Objection (even if it was founded in
Truth, which I utterly deny) the Commissioners have surely precluded
both themselves and the Nation, as with Respect to me, by their repeated
Orders and Instructions, and after leading me on for near Half a
Century, to employ my whole Time and make long Voyages for _perfecting_
the Invention, they can never be permitted now to come and say _the
Invention itself_ is good for nothing. Should any one however continue
to propagate such an Opinion, I beg leave, in Contradiction to it, to
offer that of Sir _Isaac Newton_, and that of _Martin Folkes_, _Dr.
Halley_, _Dr. Smith_, Mr. _Graham_, and eight other Persons of great
Eminence, both publicly given to the House of Commons and to be found in
the Journals, _viz._ Sir _Isaac_’s in Vol. 17, Page 677, and the others
in Vol. 29, Page 547.

The second Objection is flatly contradicted by Evidence lately before
the House of Commons, by which it appears that the Description and
original Drawings from which the Watch was made, as given in by me upon
Oath, are printed and published; and that Mr. _Mudge_ (the only one of
the Watchmakers to whom the Discovery was made, who has been examined by
the House of Commons) declar’d he could make these Watches as well as I
can. Moreover I am ready, on Condition of receiving the Remainder of
what’s due to me, upon Oath to give all manner of future Information and
Instruction in my Power; and I hope it could never enter into any Man’s
Idea of general Practicability, that I should actually teach every
indifferent Workman in the Nation, and furnish each of them with a Set
of Tools for the Trial of his Ability, at my own Expence, before I could
be entitled to the Reward.

With Regard to the third Objection, no Estimate of the future Expence
can (from the Nature of the Subject) be grounded upon any Authority
better than that of Opinion. The Price of common Watches, where each
Part is made by a different Workman, bears no Proportion to what must
necessarily be charged by any Man who was to make the whole with his
own Hands: the same Reduction will naturally take place when a Number of
Workmen are instructed to make the different Parts of these. My Opinion
is, that they might in a very few Years be afforded for about £.100
a-piece, and if a Reduction of the Machinery can be effected (which I am
strongly inclined to think is the Case, but have not had an Opportunity
of proving by Experiment for want of my Models) the Expence may be
reduced to about 70 or 80 l.

By this Time I think the Reader may naturally exclaim, How can all these
Things be? What can induce a Number of Noblemen, Statesmen and Officers
of the first Rank and most unblemished Characters; what can induce the
President of the Royal Society, and the Professors of the Universities
(to each of whom his Majesty has been most graciously pleased to order
Payment of 15 l. per Day for every Board of Longitude they attend) and
what can induce the Astronomer Royal, thus to discourage an Invention
which they are specially constituted to improve, protect, and support? I
might answer with Mr. _Maskelyne_, “that’s none of my Business to
account for.”—_The Facts are so_, and this public Relation of them is
extorted from me, by a Conviction that no other Way is left me to obtain
Justice, or so likely to prevent the Invention from perishing. However,
if it is expected of me, like Mr. _Maskelyne_, to deliver an Opinion on
this Point, I shall declare what I believe _very sincerely_, that by
far the greater Part of the Commissioners are perfectly innocent of the
Treatment I have met with: most of them are Commissioners by Virtue of
great Employments which engage their Time and Attention: A Board so
constituted is continually changing; and this being a Matter of Science
which to many may seem rather abstruse, it was very naturally left to
the Management of a few of those Members who stand in the most immediate
Relation to Science, and whose Opinions, upon a Business of this Nature,
the rest of the Board had too much Modesty to call in Question. How well
they have merited that Degree of Confidence is left to the impartial
World to determine.

To return again to Mr. _Maskelyne_’s Account: He, as I think has been
already shewn, having said and done every Thing in his Power to the
Dishonour and Discouragement of my Invention, scruples not to sum up his
Opinion of it in the following Terms:

“That Mr. _Harrison_’s Watch cannot be depended upon to keep the
Longitude within a Degree, in a _West-India_ Voyage of six Weeks, nor to
keep the Longitude within Half a Degree for more than a Fortnight, and
then it must be kept in a Place where the Thermometer is always some
Degrees above freezing: that, in case the Cold amounts to freezing, the
Watch cannot be depended upon to keep the Longitude within Half a
Degree for more than a few Days, and perhaps not so long, if the Cold be
very intense: nevertheless, that it is a useful and valuable Invention,
and in Conjunction with the Observations of the Distance of the Moon
from the Sun and fixed Stars, may be of considerable Advantage to

Having sufficiently refuted the first Part of this Opinion already, it
only remains for me to make such Remarks on the Lunar Method of finding
the Longitude, as this coupling of my Invention with it seems to call
upon me for.

It is with Reluctance that I follow Mr. _Maskelyne_ into a Subject in
which I may seem, like him, to be actuated by a selfish Preference to my
own Scheme; however, as I shall give my Reasons for what I advance, I
will not hesitate to submit them to the Public. I beg to be understood
as a warm and declared Friend to that and every other Mode which can be
devised of ascertaining the Longitude at Sea, so long as they keep
within the Bounds of Reason and Probability. Here are now two Methods
before the Public; Wou’d to God there were two Hundred! The Importance
of the Object would warrant public Encouragement to them all; but,
called upon to say something on the Subject, I think it incumbent upon
me to point out those Limits beyond which its Utility cannot, from the
Nature of the Thing, be extended.

The Method of finding the Longitude by the Moon, in which Mr.
_Maskelyne_ is in a pecuniary way interested, is this.—If the apparent
Distance between the Sun and Moon, or between the Moon and some fix’d
Star, at any certain Part of the Globe, was for every Hour of the Year
known; and if a Navigator, when at Sea, could also, by Observations,
ascertain what is the apparent Distance, at the Place where he is,
between the Sun and Moon, or between the Moon and a Star, and likewise
their respective Altitudes; and if he could also, at the same Moment,
ascertain the Time of the Day, either by an immediate Observation of the
Sun, or by a Watch which would keep Time pretty exactly from the last
solar Observation; these Matters of Fact being given, the Difference of
Longitude may from thence be calculated. I admit the Principle to be
absolutely true in Theory. The Lunar Tables, for which the Rewards have
been given, are calculated to shew the Distance between the Sun and
Moon, or Moon and Stars, at _Greenwich_; I admit the Practicability of
making such Tables; but with Regard to the other Requisites, I beg Leave
to observe that, for six Days in every Month, the Moon is too near the
Sun for observing, consequently, during those Days, the Method falls
_totally_ to the Ground; that for about other thirteen Days in every
Month, the Sun and Moon are at too great a Distance for observing them
at the same Time, or are not at the same Time visible; therefore, during
those 13 Days, we must depend upon Observations of the Moon and Stars,
and upon a Watch to keep Time, from the last Solar Observation with
sufficient Exactness, which common Watches cannot be depended upon to
do; well therefore might Mr. _Maskelyne_ admit that my Invention would
become of considerable Value, even if taken in Aid of the Lunar Tables.
I leave the Reader to judge of the Practicability of making these
Observations from what follows:

To ascertain the Longitude by the Moon and a Star, requires a distinct
Horizon to be seen in the Night, which is next to impossible, and if you
have not an Horizon, the Altitude of neither Moon nor Star can be taken:
It also requires (and this perhaps when a Ship is in a high Sea) the
Distance of the Moon and Star, in order to come at which, the Image of
one of them must be reflected through a silvered Glass, and the other
seen through an unsilvered Part of the same Glass; and they must be
brought into Conjunction in the Line that connects the silvered and
unsilvered Parts, and this to an Exactness only true in Theory, for an
Error of a Minute of a Degree committed in this Observation, will
mislead the Mariner Half a Degree in his Longitude; Now I call upon any
Astronomers of Reputation publickly to declare, that they have, even at
Land, and with the best Instruments _Europe_ affords, been able to make
this Observation of the Moon and a Star with _any thing like_ the
Precision required to determine the Longitude within the Limits
required by the Act of the 12th of Queen _Anne_; I know it cannot be
done. Nay I further call upon any such Astronomers to declare, whether
even in Observations of the Distance between the Sun and Moon, two of
them observing together have _generally speaking_ agreed in this
Observation within a Minute of a Degree: I know that in general the
Difference between the best Observers even at Land will be more, and as
a farther Proof of this Assertion, I refer the Reader to the Note
below:[6] And if these Matters of Fact are still doubted, I shall beg
Leave to call upon Mr. _Maskelyne_ and Mr. _Green_ to declare how near
they, with Admiral _Tyrrel_ agreed in determining the Longitude by the
Sun and Moon in their Voyage to _Barbadoes_; and also whether during
that Voyage they ever did determine their Longitude by the Moon and
Stars.—I know they did not, for they found the Observation too
difficult, and indeed _it is only true in Theory_.

From the foregoing Premises I infer,

1st. That during six Days in every Month, no Observations can be made by
this Method to ascertain the Longitude at Sea.

2dly, That during 13 other Days in each Month, it is impracticable to
ascertain it by this Method with any Instruments hitherto contrived, or
which the Nature of the Service to be performed seems to admit of

And 3dly, That during the remaining 11 Days in each Month, when the Sun
and Moon may, if the Weather is clear be observed at the same Time, no
Reliance can safely be placed upon the best Instruments in the Hand of
the best Observer for ascertaining the Longitude within the Limits of
the Act of Queen _Anne_; and consequently, that how valuable soever the
Lunar Tables may be for correcting a long dead Reckoning, and thereby
telling us _whereabouts_ we are, when we are not afraid of falling in
with the Land, yet even during these 11 Days, they do not extend to the
Security of Ships near the Shore.

This _Method_ of ascertaining the Longitude by the Moon has already cost
the Publick the Sum of 6,600_l._ at least, and yet no proper Experiment
has been made of it.

I shall not presume to make any Reflections on the different Treatment
the two Inventions have met with, nor will I take up more of the
Reader’s Time by a Detail of the very earnest Attention paid by the
_French_ Government to this Object. If our Rivals in Commerce and Arts
_should_ rob us of the Honour as well as the first Advantages of the
Discovery, I hope it will be admitted that the Fault is not mine: And I
likewise flatter myself that I have now furnished sufficient Materials
for the Justification of my Friends, and for shewing that the Cause
which they from publick spirited Motives had the Goodness to espouse,
was not unworthy of their Patronage.

  June 23, 1767_



    [Footnote 1: It may not perhaps be improper here to observe,
    that the Locks were such as might be picked with a crooked Nail,
    that the Lock of which the Officers had the Key was on the 10th
    of _July_ out of Order, and that Mr. _Maskelyne_ was sorry this
    should ever come to the Ear of the Publick.]

    [Footnote 2: “We whose Names are hereunto subscribed do certify,
    that Mr. _John Harrison_ has taken his Time-Keeper to Pieces in
    the Presence of us, and explained the Principles and
    Construction thereof, and every Thing relative thereto, to our
    entire Satisfaction; and that he also did to our Satisfaction
    answer to every Question proposed by us or any of us relative
    thereto; And that we have compared the Drawings of the same with
    the Parts, and do find that they perfectly correspond.”

    _August 22, 1765._

        _Nevil Maskelyne,_
        _John Michell,_
        _William Ludlam,_
        _John Bird,_
        _Thomas Mudge,_
        _William Matthews,_
        _Larcum Kendall._]

    [Footnote 3: It may not be amiss to take Notice here of an
    Objection that was raised by two of the Commissioners, both
    famous for their Knowledge in Astronomy; _viz._ That the
    Observations of equal Altitudes made at _Portsmouth_, could not
    be depended on, because the equal Altitude Instrument had been
    removed from the Place of Observation in the Morning, to another
    Place to make the Afternoon Observations; from which it is plain
    that these great Astronomers did not understand either the
    Principles or Use of one of the most simple Instruments in

    [Footnote 4: If this Interpretation of the Act was true, and the
    Commissioners had a general discretionary Power, where was the
    Reason or Use of specifying _any Trial at all_ in the original

    [Footnote 5: The Board contracted with Mr. _Kendall_ (one of the
    six Persons to whom the Discovery was made) to make a Watch
    after the Model of mine. He was to be paid for every Thing
    before-hand, and to begin in a Twelvemonth after making the
    Bargain; he is to make Parts like Parts, but is not to be
    answerable for his Watch’s going at all. My Timekeeper is now in
    his Possession, tho’ he is not yet ready to make Use of it;
    There are some Parts in the making of which the Model can be of
    little or no Use to him; I only desired it for six or eight
    Months, and am confident he can have no Occasion for it before
    that Time is expired: however I have offered to have it forth
    coming whenever Mr. _Kendall_ declares that he wants it,
    therefore I apprehend their Engagements with Mr. _Kendall_
    afford no solid Reason for the Commissioners to refuse lending
    it to me.]

    [Footnote 6: In the fifth Volume of M. DE LA CAILLE’s
    Ephemerides, Page 31, he says, “that any Person would be in the
    wrong to suppose that the Longitude at Sea can be determined by
    the Moon, to a less Error than two Degrees, let the Method which
    is employed be never so perfect, let the Instruments, of the
    Sort now in use, be never so excellent, and let the Observer be
    the most able and accomplished. For if we examine, without
    prejudice, all the Circumstances which enter into the
    Calculation and into the Observation of a Longitude at Sea, we
    shall be easily convinced, that it would be ridiculous to
    maintain, that the Sum of the inevitable Errors should not
    amount to five Minutes of a Degree, that is, to two Degrees and
    a half of Longitude.” _N. B._ M. DE LA CAILLE published this in
    the Year 1755, and is universally allowed to have been an
    excellent Observer, and made several Voyages by Sea, where he
    made Trials of this Method by the Moon.

    Dr. HALLEY and Dr. BEVIS (as appeared to the Honourable House of
    Commons upon an Examination of the latter) did, with an
    excellent HADLEY’s Quadrant, rectified by Mr. HADLEY himself,
    and in his presence, attempt to take the angular Distance of the
    Moon from ALDEBARAN, a Star of the first Magnitude; but with
    such bad Success (some of the Observations removing GREENWICH
    from itself almost as far as PARIS) that Dr. HALLEY seemed to be
    out of Hope of obtaining the Longitude by this Method.]

Transcriber’s Notes: This ebook has been transcribed from the original
print edition, published in 1767. Obvious printing errors have been
corrected, while minor irregularities in the spelling have been
retained. The table below lists all corrections applied to the
original text.

p. 9: the Rest of the Summer -> The Rest
p. 11: [added comma] his Integrity, Disinterestedness and Ability
p. 13: a set of Observavations -> Observations
Footnote 6: [added closing quotes] to two Degrees and a half of Longitude.”

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