Note 126 — MEMOIRS OF THE LIFE OF DAVID RITTENHOUSE; ANTERIOR TO HIS SETTLEMENT IN PHILADELPHIA.

According to Mr. Lalande, (in his Astronomie, vol. ii.) the transit of Venus over the Sun, in 1639, observed by only Messrs. Horrox and Crabtree, two Englishmen, and which was the first ever observed, was seen in consequence of a fortunate accidental circumstance. He says, that Horrox had been occupied in making calculations for an almanack, from the Tables of Lansbergius, which are much less perfect than the RudolphineRudolphine Tables: that these Tables of Lansbergius were in an error of 16′ for the latitude of Venus, while the RudolphineRudolphine Tables had an error of only 8′; but the one of Lansbergius made Venus pass on the sun in such a way, as that the transit ought to be visible; whereas the tables of Kepler represented the planet as passing below him; and thus it was, remarks Lalande, that bad tables occasioned a good observation. Relying on these tables, which Lansbergius had extolled with a confidence likely to produce imposition, Horrox prepared himself to observe that transit; and on the 24th of November, it took place at the time he expected, Venus being about half an hour on the sun when he set. He had sent on the occasion to his friend Crabtree, who was at Manchester, some miles from Hoole: and he observed the transit, likewise; though very imperfectly, by reason of intervening clouds. W. B.