*SKETCH OF JOHN COUCH ADAMS.*

A part of his work in it was to lecture during one term in each year, generally on the lunar theory, but sometimes on the theory of Jupiter's satellites or the figure of the earth.

In 1867 he published an account of the results he had obtained with respect to the orbit of the November meteors, in the investigation of which he had co-operated with Prof. H. A. Newton, using the data and observations furnished by him. These calculations took notice of all the perceptible effects produced by the planets, and established the correctness of the period of thirty-three and a quarter years for the revolution of the meteoric body. In order to obtain a sufficient degree of approximation, it was necessary to break up the orbit of the meteors into several different parts, for each of which separate calculations had to be made. Prof. Adams afterward subdivided certain parts of the orbit of the meteors into still smaller portions, with a view of obtaining a closer approximation. The calculations on this subject have not been published, but they exist among his papers, and seem to be fairly complete.

A paper communicated to the Astronomical Society, in November, 1877, embodied a review of a memoir by Mr. G. W. Hill, of Washington, on the part of the motion of the moon's perigee, which is a function of the mean motions of the sun and moon. This paper is pronounced by Prof. Glaisher peculiarly interesting, because in it the author expresses his own views with respect to the mathematical treatment of the theory of the moon's motion. He seems to have preferred to treat the subject by its special problems; while he had great admiration for Delaunay's general theory.

Prof. Adams also paid much attention to pure mathematics, and treated many abstruse problems in a highly technical manner, in papers the very titles of which are an unknown language to all but accomplished mathematicians.

A large mass of papers which Sir Isaac Newton had left at his death, having been left to the University of Cambridge by Lord Portsmouth, it became Prof. Adams's task to arrange and catalogue the mathematical part of the collection. The work lasted many years, but proved very interesting to Prof. Adams, by casting light on the methods by which Newton had worked out his results.

On the resignation by Prof. Challis of the directorship of the observatory at Cambridge in 1861, Prof. Adams was appointed to succeed him, while he still continued in the Lowndean professorship. In 1870 the observatory began to co-operate in the scheme of the *Astronomische Gesellschaft* for the observation of all the fixed stars in the northern hemisphere down to the ninth magnitude, the observations being put under the charge of the first