constituting in part a new elaboration of celestial mechanics, and is famous for his theoretical discovery of Neptune. John Couch Adams (1819–1892) of Cambridge
divided with Le Verrier the honour of the mathematical discovery of Neptune, and pointed out in 1853 that Laplace's explanation of the secular acceleration of the moon's mean motion accounted for only half the observed acceleration.
Charles Eugène Delaunay (born 1816, and drowned off Cherbourg
in 1872), professor of mechanics at the Sorbonne in Paris, explained most of the remaining acceleration of the moon, unaccounted for by Laplace's theory as corrected by
Adams, by tracing the effect of tidal friction, a theory previously suggested independently by Kant, Robert Mayer,
and William Ferrel of Kentucky. George Howard Darwin of
Cambridge (born 1845) made some very remarkable investigations in 1879 on tidal friction, which trace with great certainty the history of the moon from its origin. He has since studied also the effects of tidal friction upon other bodies in the solar system. Criticisms on some parts of his researches have been made by James Nolan of Victoria. Simon
Newcomb (born 1835), superintendent of the Nautical Almanac
at Washington, and professor of mathematics at the Johns Hopkins University, investigated the errors in Hansen's tables of the moon. For the last twelve years the main work of the U. S. Nautical Almanac office has been to collect and discuss data for new