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84 astronomical observations upon comets, transits, and eclipses, and similar abstruse topics. Even during the trying period of 1776, 1777, and 1778, while these publications were suspended, and the war was surging around his own home, he and Smith, Lukens, and Biddle found time to note, some observations upon a transit of Mercury and two eclipses of the sun. Within a week after the evacuation of Philadelphia by the British, Rittenhouse was in the city, seated by his telescope, watching an eclipse. In 1776 he wrote a defence of the Newtonian system for the Pennsylvania Magazine, and in 1782 invented a wooden hygrometer. From 1779 to 1782 he was Professor of Astronomy in the University of Pennsylvania, and also a trustee and vice-provost of the same institution.

In this connection an interesting incident is narrated in the Life and Times of Dr. William Smith. The announcement of the death of Franklin was brought by a messenger to a party of gentlemen, consisting of Thomas McKean, Henry Hill, Thomas Willing, Rittenhouse, and Dr. Smith, who were dining with Governor Thomas Mifflin, at the Falls of Schuylkill. A fierce thunderstorm happened to be raging at the same time. Impressed by the event and the circumstances under which they heard it, Smith wrote at the table this impromptu:

He succeeded Franklin as president of the American Philosophical Society upon the death of the latter in 1790. He was elected a fellow of the Academy of Arts and