LIFE IN MARS. 121 



Martial atmosphere that the spectroscope can inform 

 us about. Our spectroscopists know quite well what 

 the vapour of water is capable of showing in the rain- 

 bow-tinted streak which is called the spectrum. When 

 white light is caused to shine through a sufficient quan- 

 tity of the vapour of ^ater, the rainbow-tinted streak 

 forming the spectrum of white light is seen to be 

 crossed by certain dark lines, whose position and 

 arrangement there is no mistaking. Now the light we 

 get from Mars is reflected sunlight, but it is sunlight 

 which has been subjected to more than reflection, since 

 it has passed twice through the depths of the Martial 

 atmosphere, first while passing to his surface, and 

 secondly while leaving that surface on its voyage 

 towards ourselves. If that double passage have carried 

 it through the vapour of water, the spectroscope will 

 certainly tell us of the fact. 



Let us see how this problem was dealt with by our 

 most skilful spectroscopist, Dr. Huggins, justly called 

 the Herschel of the spectroscope. The following account 

 is an epitome of his own narrative : ' On February 14 

 he examined Mars with a spectroscope attached to his 

 powerful eight-inch refractor. The rainbow-coloured 

 streak was crossed, near the orange part, by groups of 

 lines agreeing in position with those seen in the solar 

 spectrum when the sun is low down and so shines 

 through the vapour -laden lower strata of our atmo- 

 sphere. To determine whether these lines belonged 

 to the light from Mars or were caused by our own 

 atmosphere, Dr. Huggins turned his spectroscope 



