In the annular eclipse of the sun, on the 3d of April, 1791, as observed at Philadelphia by Mr. Rittenhouse, the formation of the ring is stated at 6^h 46′ 11½″ A. M. true time; and its rupture, at 6^h 50′ 28″. “I have,” says Mr. Lalande (in his _Additions_, 1797,) “reduced the conjunction of it to 7^h 41′ 19″, and the difference of meridians 5^h 10′ 3″, greater by 7″ than that given by Mr. Rittenhouse. This duration of the ring, gives for the latitude in conjunction 44′ 57″, which confirms the value of the diameters of the sun and of the moon, that I have given in the 3d edition of my _Astronomy_, and the diminution that I make in the eclipses, 3½″ for the ray of the sun, and 2″ for that of the moon. I have subtracted one minute of the time marked in the third volume of the Transactions of the Society of Philadelphia, for the formation and the rupture of the ring; but this correction was pointed out to me by the termination of the eclipse, as well as by the difference of meridians, which was ascertained by the Transit of Venus over the Sun.” Footnote 294: Mr. Lalande was first appointed to that station, in the year 1761. “The College of France,” heretofore styled “The Royal College of France,” was originally founded in the year 1530, by Francis I. but letters patent were issued in favour of it in 1772, by the unfortunate Louis XVI. The present edifice, finished in 1775, gave new activity to the ancient establishment; and Lalande viewed it, when he wrote his _Astronomie_, as having been one of the best schools in the world for the sciences, but principally for astronomy. ----- The mind of Dr. Rittenhouse, ever intent on doing, good, was always zealously engaged on occasions which afforded him opportunities of contributing to the rewards of merit and the promotion of beneficial establishments, or useful undertakings of any kind. Such an occasion presented itself, at the close of the year 1795. His nephew Dr. B. S. Barton, to whom he was attached by the strongest ties of friendship, then held the Professorship of Botany and Natural History in the University of Pennsylvania: but a vacancy being at that time expected in the chair of the Materia Medica, which branch of medicine was then taught by Dr. Samuel Powell Griffitts, Dr. Rittenhouse exerted himself to obtain that appointment for his nephew; upon whom it was conferred soon after, in conjunction with the chair he already occupied. With a view to the gratification of his anxious wishes, in the attainment of this object, Dr. Rittenhouse addressed himself personally to some of his colleagues in the board of trustees of the University: and to Dr. M‘Kean, president of that board, he wrote the following letter[295] on the subject. ----- Footnote 295: