In the Rev. Mr. Vince’s great work, entitled, A Complete System of Astronomy, (and contained in “A Treatise on Practical Astronomy,” at the end of the second volume of that work,) is an entire chapter on “Hadley’s Quadrant;” giving a particular description of the instrument, with rules for the computations from the observations and illustrations of them by examples. In this Treatise, the author says, that the instrument took its name from the “inventor,” John Hadley, Esq. and observes, that not only the science of navigation is greatly indebted, to this “incomparable instrument,” but such are its various uses in astronomy, that it may not improperly be called “a portable observatory.” Mr. Vince further observes, that in the year 1742, about ten years after Mr. Hadley’s invention (for so he styles it) was published, a paper in Sir Issac Newton’s own hand-writing was found among Dr. Halley’s papers, after the Doctor’s death, containing a figure and description of an instrument (referring to Philos. Transactions, No. 465,) not much different in its principle from this of Hadley. He adds, that as Dr. Halley was alive when Mr. Hadley’s instrument was shewn to the Royal Society, and he took no notice of this paper of Sir Isaac Newton, it is probable he did not know there was such an one. In another part of his work (under the head of The History of Astronomy, vol. ii. p. 280.) Mr. Vince asserts, that the first person who formed the idea of making a Quadrant to take angles by reflection, was Robert Hook; and he was born in 1635. On the whole, however, the learned author draws this conclusion:—“Both Sir Isaac Newton and Mr. Hadley therefore seem entitled to this invention.”
Mr. Lalande, speaking of this instrument, says: “Le[“Le] Quartier de Reflexion, exécuté en 1731 par Hadley, a donné un moyen facile de mesurer les distances sur mer, à une minute pris, aussi bien determiner le lieu de la Lune en mer.” See his Astronomie, vol. iii. p. 654.
From these facts, and a careful examination of the papers themselves, here quoted and referred to, the scientific reader will be enabled to decide upon the true merits of the controversy that has so long subsisted, concerning the respective claims of Godfrey and of Hadley, to the invention of the instrument that bears the name of the latter.
Before this subject is dismissed, however, it will not be deemed improper to add, that the late Dr. John Ewing communicated to the Am. Philosophical Society an account of an Improvement in the construction of (what he terms) “Godfrey’s double reflecting Quadrant,” which he had discovered in the spring or summer of the year 1767: this will be found in the first volume of the Society’s Transactions. In the conclusion of this communication, Dr. Ewing says:—“This improvement of an instrument, which was first invented and constructed by Mr. Godfrey of this city, and which I do not hesitate to call the most useful of all astronomical instruments that the world ever knew, I hope will make it still more serviceable to mankind.”
This communication to the Society by Dr. Ewing, was made in the year 1770. In one concerning the comet of that year, and made by Dr. Rittenhouse about the same time, the instrument to which Dr. Ewing’s improvement applies, is called Hadley’s Quadrant: but perhaps Dr. Rittenhouse so named it, in conformity to common usage.
[A36]. This I know has been pretended to. But it is easy to make geometrical conclusions come out as we would have them, when the data they are founded on, are so uncertain that we may chuse them as suits our purpose.
[A37]. This circumstance tends gradually to lessen the variety of the seasons.
[A38]. This was Tobias Mayer, who was born at Marbach in the principality of Wurtemberg, in the year 1723: he rendered himself celebrated in astronomy, by having calculated the best tables of the moon, and by an excellent catalogue of stars. He died at Gottingen in 1762, at the age of thirty-nine years. W. B.
[A39]. It may happen that any of the planets, about the time they become stationary, shall describe a loop about some small fixed star, in such manner as might be easily mistaken for the star making part of a revolution about the planet. This I suspected to have been the case with the above observation of Montaigne. But the times set down do not confirm the suspicion.