Giovanni Battista Donati, an Italian astronomer, born in Pisa in 1826, died in Florence, Sept. 20, 1873. In 1852 he became an assistant in the observatory of Florence, where ho soon gained distinction, especially by his discovery, on Juno 2, 1858, of the comet which bears his name. He had been anticipated in a similar discovery made in 1854; but he established his claims of priority in those seen by him on June 3, 1855, Nov. 10, 1857, and July 23 and Sept. 9, 1864. He also made important investigations on the spectra of comets, the solar disk, and the stars, and in 1862 published Spectra di quindici stelle. In 1864 he visited England, and in the same year succeeded Prof. Arni as director of the observatory of Florence. Through his exertions was inaugurated in 1872 the royal observatory on the hill of Arcetri, near Florence, memorable as the site of Galileo's tower. He was director of this and professor of astronomy in the royal institution of Florence at the time of his death, just previous to which he had represented Italy in the international meteorological congress at Vienna.