Page:Hector Macpherson - Herschel (1919).djvu/42



result of Herschel's fame as the founder of stellar astronomy has been that his greatness as an observer and student of the Sun and planets has been largely overlooked. Nevertheless his work in solar and planetary astronomy alone would have gained for him the highest position among the astronomical observers of the day. "Among the celestial bodies," he wrote in 1799, "the Sun is certainly the first which should attract our notice." From an early date he was attracted by solar phenomena, and in the course of his career contributed several papers on the Sun to the Royal Society. In the first of these, "On the Nature and Construction of the Sun and Fixed Stars," read 18th December, 1794, he propounded his hypothesis of the Sun's constitution, to which he adhered throughout his lifetime.

Before Herschel's time, the Sun had been observed by Galileo, Scheiner, Fabricius, Hevelius, Cassini and others. Sun-spots had been observed for over a century and a half and many important details had been detected, but concerning their nature controversy had raged and uncertainty prevailed. In 1774, just at the beginning of Herschel's career as an observer, the well-known theory of sun-spots was propounded by Alexander Wilson, Professor of Astronomy in the University of Glasgow. A series of observations convinced him that the spots were depressions beneath the general surface of the Sun; not mountains, as many observers had supposed, but cavities in the glowing surface through which the darker