Note 88 — MEMOIRS OF THE LIFE OF DAVID RITTENHOUSE; ANTERIOR TO HIS SETTLEMENT IN PHILADELPHIA.
Reading edition
For the use of such readers as may not be acquainted with the Latin language, the following translation of the above is given, from the original of Mr. de Zach.
“Concerning the means of determining the longitude, this is not the proper place to treat: of one, however, the marine or nautical time-keeper, it will not be foreign to our purpose to say something.
“It is now about thirty years, since those very ingenious makers of time-keepers, Harrison, Cummings, Kendal, Arnold, and Mudge, among the English,—Le Roy, and Berthoud, among the French,—devised various and excellent ones for the use of navigators, and brought to a great degree of perfection those marine watches, called by the English, Time-keepers. As every one knows their use in ascertaining the longitude, on a sea-voyage, I shall not say any thing more of them here.—A similar time-piece, made by the celebrated watch-maker Mr. Thomas Mudge, and often referred to in the royal observatory of Greenwich, was, in 1784, made use of by the Hon. Vice-Admiral (John) Campbell, commander of the naval squadron[88a] on the Newfoundland station,—going thither and returning; and from that time was diligently examined, at the observatory of his Excellency Count Bruhl, in Dover street London.
“This very marine time-piece was confided to my charge, in the year 1786, for the purpose of determining the longitudes of my journey by land; when, called from London by his Serene Highness the Duke of Saxe-Gotha,—the patron of all the sciences and liberal arts, but more especially favouring astronomy,—I returned to Germany; where the erecting of a complete and splendid Observatory, at Gotha, was placed under my direction.[88b] I then took with me, by the command of his Serene Highness, a watch of a smaller size, which he usually carried in his fob,—called by the English a Pocket-chronometer,—made by a London artist, Mr. Josiah Emery:[88c] which, being made with the greatest accuracy and ingenuity, yielded nothing in point of correctness to the larger nautical time-keepers, as may be seen from three tables of their movements by the illustrious Count Bruhl, and also of others, by Dr. Arnold, lately established by authenticated certificates.
“About the end of the year 1786 and the beginning of 1787, I accompanied His Serene Highness, in a tour through Germany, France and Italy. In this journey, the longitudes of several places and astronomical observatories were determined, from a comparison of the time of a nautical time-keeper (which was set by the solar mean time in Dover street, London,) with the mean time of the place; which appears by the altitudes of the sun, by Hadley’s sextant—those which we call corresponding, or by a comparison with it, as transmitted to us in observatories, by those astronomers. By the same instruments, therefore, when I arrived at Gotha, I ascertained the longitude of the future observatory there, with the greatest care and attention; which the Duke, going to London a few days after, taking with him his chronometer, at length fully verified.”