Part 82

16. Astronomical Observations made at Philadelphia: viz. of a Lunar Eclipse, on the 2d of November, 1789; of the Transit of Mercury over the Sun’s disk, on the 5th of November, 1789; of an Eclipse of the Moon, on the 22d of October, 1790; of an Eclipse of the Sun, on the 6th of November, 1790; and of an Annular Eclipse of the Sun, on the 3d of April, 1791: with an Account of corresponding Observations of the two first of these Phænomena, made at the University of William and Mary in Virginia, by the Rev. Dr. Madison; and of the second, alone, made at Washington-College in Maryland, by the Rev. Dr. Smith: communicated by D. Rittenhouse. Read, February 4. 1791.

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Footnote 330:

This eclipse was observed by Andrew Ellicott, Esq. at the city of Washington, as follows; viz.

{ 6.^h 39′. 1″,25 } Annulus completed } April 3d. { 6. 43. 15,25 } Do. broken } M. Time. { 7. 55. 37,75 } End of Eclipse. }

A letter from the celebrated French Astronomer, Lalande, to Dr. Rittenhouse, on the same subject, has been already given.

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17. A Letter from Dr. Rittenhouse to Mr. Patterson, relative to a Method of finding the Sum of the several Powers of the Sines, &c. Read, May 18. 1792.

18. An Account of a Comet, (first observed by Mr. Rittenhouse, on the 11th of January, 1793:) in a letter from D. Rittenhouse to Mr. Patterson. Read, February 15. 1793.

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Footnote 331:

In this letter, Dr. Rittenhouse merely informs Mr. Patterson, in general terms, of the time when he first observed this comet, its then place, and its course through several of the constellations, until the 8th of February; on the evening of which day, he saw it for the last time. It is presumed that Dr. Rittenhouse’s state of health, at that period, would not admit of his making more definite observations on this comet.

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The fourth volume, printed in the year 1799, (three years after Dr. Rittenhouse’s death,) contains—

19. A paper, “On the Improvement of Time-keepers;” by David Rittenhouse, LL. D. Pres. Am. Philos. Society. Read, November 7. 1794.

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Footnote 332:

This desideratum in astronomical science had long engaged Dr. Rittenhouse’s attention; and it is confidently said by one of his intimate friends, that, in the latter part of his life, he had actually written much on the subject of Pendulums; intended, probably, for publication. But, unfortunately, the manuscript-book, which contained what he had thus written, can not now be found.

In the paper mentioned in the text, he remarks, that “the invention and construction of time-keepers may be reckoned among the most successful exertions of human genius. Pendulum-clocks especially,” says he, “have been made to measure time with astonishing accuracy; and, if there are still some causes of inequality in their motions, the united efforts of mechanism, philosophy and mathematics, will probably, in time, remove them.”

Indeed no man has done more, none perhaps so much, towards removing the imperfections in chronometers, to which he alludes, as this great mechanician himself. His admirable time-piece, now in the possession of the Philosophical Society at Philadelphia, constructed by him, on an improved plan of his own, affords ample proof of the “astonishing accuracy” (as he expresses it) to which the pendulum-chronometer may be brought. A description of the mechanism of this extremely accurate time-piece, as well as of the principles on which its superior correctness depends, is inserted in the Appendix.

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20. A paper, “On the Expansion of Wood by Heat;” in a letter from David Rittenhouse, LL. D. Pres. Am. Philos. Society. Dated, May 15. 1795.

21. A Method of raising the common Logarithm of any number immediately; by D. Rittenhouse, LL. D. Pres. Am. Philos. Society. Read, August 12. 1795.

22. A communication, “On the Mode of determining the true Place of a Planet, in an eliptical Orbit, directly from the mean Anomaly by Converging Series;” by David Rittenhouse, Pres. Am. Phil. Society. Read, February 5. 1796.

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This last communication was made to the Society, within five months of the time immediately preceding Dr. Rittenhouse’s death.

It is a strong evidence not only of our Philosopher’s industry, but of his attachment to that institution of which he was so great an ornament, that, in the course of the twenty-six years during which he was a member of it, he could find sufficient leisure,—almost constantly employed, as he was, in important public business, and frequently bereft of health,—to contribute so many valuable papers as he did, to the too scanty stock of its published Transactions. Dr. Franklin, who was a member of the Philosophical Society, and their president, for twenty-one years, furnished them with only eight communications during that time: and Mr. Jefferson, who has nominally occupied the president’s chair in the same Society above sixteen years, has favoured them with only two or three, within this period.

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