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.

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