tion of the stars, one might calculate the geographical position of the spot where he happened to he. He sought to know why this was so. For this purpose he had to study mathematics from its rudiments, and was thus led up rapidly to spherical astronomy. He had to be continually introducing the elements of the position of the sun and moon into his calculations, taking them from an astronomical calendar. He desired to calculate these elements for himself. He was thus led to study the laws of the motions of the celestial bodies. The net which astronomical science had cast over him was thus wrapping him closer every day, and in less than a year after he had begun his astronomical studies he undertook the computation of the orbit of the comet of 1607, a work that involved three hundred pages of calculations, and which a skilled astronomer might regard as the task of a year. He was not a little proud of his calculations when he had completed them, and he determined to make the acquaintance of Olbers, who was practicing medicine in Bremen, and was regarded as the first authority in everything that related to comets. Meeting the famous doctor in the street, he timidly told him he had calculated the orbit of a comet, and asked him to have the kindness to examine his work. Olbers granted the request, supposing that he was about to receive the work of an amateur, whom he must treat politely, for fear of discouraging him. But he was greatly surprised when he examined the calculations, and he immediately wrote to Bessel: "I have read your work on the comet of 1607 with very great pleasure. It gives me a very high idea of your astronomical and mathematical knowledge, and of your skill in the most difficult departments of calculation. If I should criticise you on any point, it would be only on your having given more time and care to the ancient observations than they deserve." If we place this praise of Olbers by the side of the fact that Bessel did not know a word of mathematics or astronomy a year before, or hardly that there was such a thing as the mechanics and mathematics of the sky, and if we also recollect that he was occupied from eight o'clock in the morning till night with something entirely different, we can gain a slight idea of the great energy and the rare mental constancy which he must have displayed, and which afterward carried him so far.
Bessel's fate was decided. He was recommended by Olbers to Gauss, who, in the same year, invited him to assist him in the calculations with which he was occupied. Bessel accepted the invitation with enthusiasm, and, according to his habit, made the calculations with more precision than was required. From that time Gauss and Bessel were connected in a lasting scientific friendship. Bessel was to wait another year before giving himself up entirely to astronomy, but early in 1806, warmly supported by Olbers, he was appointed inspector of a private observatory at Lilienthal. He remained there four years, till his reputation brought him a call to the direction of the new ob-
