Page:Lectures on Ten British Physicists of the Nineteenth Century.djvu/133

 years later he succeeded Challis as the Director of the Cambridge Observatory and settled down as a married man. Henceforth the center of his scientific activity was the Observatory house, where Airy and Challis had lived, situated on an eminence about a mile west of Cambridge on the Huntington road. The observatory was well equipped, thanks to Airy's efficient incumbency; but Adams was by nature a calculator, and the instruments were not much used during his tenure of office.

In 1866 Adams took up the problem of the November meteors, drawn thereto by the remarkable display of that year. Prof. Newton of Yale had published a memoir in the American Journal of Science and Arts in which he collected and discussed the original accounts of thirteen displays of these meteors in years ranging from 902 to  1833; he inferred that these displays recur in cycles of 33.25 years, and that during a period of two or three years at the end of each cycle a meteoric shower may be expected. He concluded that the most natural explanation of these phenomena is, that the November meteors belong to a system of small bodies describing an elliptic orbit about the Sun, and extending in the form of a stream along an arc of that orbit which is of such a length that the whole stream occupies about one-tenth or one-fifteenth of the periodic time in passing any particular point. He showed that in one year the group must have a periodic time of either 180.0 days, 185.4 days, 354.6 days, 376.6 days or 33.25 years. Prof. Newton found that the node of the orbit of the meteors is gradually increasing; that the rate is 52″.4 with respect to the fixed stars; and he remarked that with this datum and the position of the radiant point, computation might be able to determine which of the five periods is the correct one. He considered 354.6 days the most probable. Adams then took up the problem. He found that none of the first four periods satisfied the data, while the fifth one of 33.25 years did. He concluded that he had settled the question of the periodic time of the November meteors beyond a doubt. The elements of their orbit obtained by Adams agreed very approximately with those of a comet