THE INNER PLANETS. 95 



reality of the canals, in spite of the ridicule 

 cast on them and their observers, and conse- 

 quently the truth of the theory of intelligent life 

 in Mars. 



Meanwhile the old-fashioned Martian obser- 

 vations have been continued in less favourable 

 climates than Arizona and Italy by various 

 astronomers, among them the famous Camille 

 Flammarion, the American astronomers James 

 Edward Keeler (1857-1900), Edward Emerson 

 Barnard (born 1857), the English astronomer 

 W. F. Denning, and others. These conscientious 

 and painstaking observers have done much for 

 Martian study in increasing the number of 

 accurate delineations of the Martian surface. 



The spectrum of Mars was first examined by 

 Huggins in 1867. He found distinct traces of 

 water-vapour, and this was confirmed by Vogel 

 in 1872, and by Maunder some years later. In 

 1894, however, William Wallace Campbell (born 

 1862), the American astronomer, observing from 

 the Lick Observatory, California, was unable to 

 detect the slightest difference between the spectra 

 of Mars and the Moon, indicating that Mars had 

 no appreciable atmosphere ; and from this he de- 

 duced that the Martian polar caps could not be 

 composed of snow and ice, but of frozen carbonic 

 acid gas. In 1895, however, Vogel confirmed his 



