readers may also consult the abstracts of Herschel's memoirs, which have been given in "A Subject-index and a Synopsis of the Scientific Writings of Sir William Herschel," prepared by Dr. Hastings and myself, and published by the Smithsonian Institution.
An accurate sketch of the state of astronomy in England and on the Continent, in the years 1780–1820, need not be given. It will be enough if we remember that of the chief observatories of Europe, public and private, no one was actively devoted to such labors as were undertaken by Herschel at the very beginning of his career.
His observations on variable stars, indeed, were in the same line as those of Pigott; Flaugergues and Darquier, in France, had perhaps preceded him in minute scrutiny of the sun's surface, etc.; but, even in that department of observation, he at once put an immense distance between himself and others by the rapid and extraordinary advances in the size and in the excellence of his telescopes. Before his time the principal aids to observation were the Gregorian and New-
