Part 1

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REMARKS ON A PAMPHLET

Lately published by the Rev. Mr. _MASKELYNE_,

Under the AUTHORITY of the BOARD OF LONGITUDE.

By JOHN HARRISON.

THE SECOND EDITION.

_LONDON:_ Printed for W. SANDBY in Fleetstreet. MDCCLXVII.

(PRICE SIXPENCE.)

REMARKS, ON A PAMPHLET, &c.

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 Longitude.

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 deg.. 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 Contradiction.

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 me.