Angelo Secchi was born in 1818 at Reggio, in the Emilia. Educated in the Collegio Romano, he was ordained priest in 1847, but his love of science, and particularly astronomy, dates from the beginning of his career. In 1849 he succeeded Di Vico as director of the Observatory of the Collegio Romano. This post he filled with conspicuous ability for a period of twenty-nine years, until his death on February 26, 1878. To Secchi is due the credit of the first spectroscopic survey of the heavens. He reviewed the spectra of 4000 stars, and classified them into four distinct groups, which are recognised to this day. The first type embraces over half of those which Secchi examined. This type is represented by Sirius, Vega, Altair, and other bluish-white stars, and is characterised by the intensity of the hydrogen lines. The second type embraces the yellow stars, such as Capella, Arcturus, Aldebaran, Pollux, and the Sun itself, and is known as the Solar type. The spectra of these stars closely resemble that of the Sun, and are distinguished by innumerable lines. Secchi’s third type, or red stars, represented by Betelgeux, Antares, and others, are characterised by strong absorption bands, and the spectra have been described as “fluted.” The third-type stars are comparatively scarce compared with the first and second, and the fourth is even less numerous. The fourth-type stars are also red with broad absorption lines. To Secchi’s four types a fifth was added in 1867 by Wolf and Rayet of Paris Observatory—namely, the gaseous stars. Secchi aimed at a comprehensive survey of the stellar spectra, and he accomplished much valuable work. He did not devote his time to analysing individual stars. This branch of study—analysis of spectra and the determination of the elements in the stars—was undertaken by his contemporary, William Huggins, one of the greatest astronomers whom England has ever produced. Born in London in 1824, William Huggins commenced his astronomical researches at the age of twenty-eight. In 1856 he erected, at Tulse Hill, London, an observatory which he equipped at great expense. He commenced observations on the usual astronomical lines, taking times of transits and making drawings of the surfaces of the planets. But he soon tired of the routine of ordinary astronomical work, and on the publication of Kirchhoff’s explanation of the Fraunhofer lines in the solar spectrum, he commenced to investigate the spectra of the stars. Having constructed a suitable spectroscope, he commenced observations in 1862 in conjunction with his friend, William Allen Miller, Professor of Chemistry in London. He exhaustively investigated the two red stars, Betelgeux and Aldebaran, ascertaining the existence in the former star of sodium, iron, calcium, magnesium, and bismuth; and in the latter star the same elements, with the addition of tellurium, antimony, and mercury.