*THE POPULAR SCIENCE MONTHLY.*

science for his labors, Prof. Adams subscribed bis name, writing beneath it the motto, "*Hommage au compatriote de Leverrier.*"

The small number and volume of Prof. Adams's publications, after his calculations for the planet Neptune, have been remarked upon. He was, however, an industrious worker, calculating in every quarter of the mathematical field and in mathematical astronomy, and is said to have left a large mass of manuscript work, much of which is expected to prove valuable. The Adams prize, of about four hundred dollars a year, to be awarded every two years to the author of the best essay on some subject of pure mathematics, astronomy, or other branch of natural philosophy, was instituted by members of St. John's College soon after the discovery of Neptune, as a testimonial to the honor conferred on the college and the university by the investigation. In 1848 Mr. Adams began the determination of the constants in Gauss's theory of terrestrial magnetism. He resumed the work and was occupied with it in the later years of his life, but had not completed it at the time of his death. In 1852, having been elected in the previous year President of the Royal Astronomical Society for two years, he communicated to the society new tables of the moon's parallax, to be substituted for those of Burckhart. These tables were printed in the appendix to the Nautical Almanac for 1856.

His memoir explaining the secular variation of the moon's mean motion was communicated to the Royal Society in 1853. The problem baffled solution. The French Academy had at different times given prizes for explanations to Euler and Lagrange, but neither of these mathematicians had been able to discover any secular term; and Euler, considering it established that such a term could not be produced by the principles of gravitation, had recourse to the supposition of a resisting medium. Laplace announced in 1787, as the true cause of the phenomenon, the gradual diminution in the mean action of the sun produced by the secular variation of the eccentricity of the earth's orbit. Theories were also proposed by Damoiseau and Plana, agreeing in principle with Laplace's, but differing slightly in the numerical values assigned to the acceleration. Adams found that Laplace's explanation of the phenomena was essentially incomplete, and suggested corrections to all the theories. Some controversy ensued, at the end of which Prof. Adams was sustained. A calculation of the same problem, made by Prof. Airy in 1880, was also corrected by Prof. Adams.

Mr. Adams was appointed, in the fall of 1858, Professor of Mathematics in the University of St. Andrews, where he continued his lectures till the end of the session, in May, 1859; and late in 1858 he was made Lowndean Professor of Astronomy and Geometry at Cambridge. He held the last position till his death.