“It is a long time, my dear Associate, since I have heard from you: but Mr. Adet, our worthy ambassador, will probably procure for me that satisfaction. You will see by the little history which I send you, that the troubles of the revolution have not impaired my labours; and that I have, now, twenty-seven thousand stars, observed.
“I have seen with great pleasure, in the transactions of your Philosophical Society, the annular eclipse of 1791:[[292]] I have calculated the conjunction 7h 42′ 19″; but I have been obliged to take one minute from the phases of the ring, and to suppose {6h 49′ 30″} / {6h 53′ 47″}, in order to agree, either with your end of the eclipse, or the difference of meridians, already known with sufficient accuracy by the transit of Venus, which gives 9h 10′ 6″; and your eclipse gives, 9h 10′ 3″, or 5h 0′ 43″ in relation to Greenwich.
“What has given me still greater pleasure, is, that the duration of the ring, as you observed it, agrees very well with the diameters of the Sun and of the Moon, which T have adopted in the third edition of my Astronomy (1792), and the diminutions that I there propose for eclipses; viz. 3″½ to be taken from the diameter of the Sun, and 2″ from that of the Moon.[[293]]
“I pray you to make many compliments for me, to the astronomers whom I know, in your country, Mr. Willard at Beverley and Mr. Williams at Cambridge: Is there any other astronomer, now, who applies himself seriously to astronomy? I greet you with health and brotherhood.
“Lalande.
“Professor of Astronomy, and Inspector of the
College of France,[[294]] Cambray Place.“
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.