6o 



THE ORIGIN AND EVOLUTION OF LIFE 



the hydrogen atom: they are hberated from metals on which 

 ultra-violet light falls, and can be released from atoms of mat- 



FiG. 6. H\T)ROGEN Vapor in the Solar Atmosphere 



Hydrogen, which far exceeds any other element in the amount of heat it yields upon 

 oxidation (see Table II, p. 67) and ranks among the four most important of the chemical 

 life elements, is also invariably present at the surface of all typical hot stars, includ- 

 ing the sun. The large masses of hydrogen vapor known as "solar prominences" 

 which burst forth from ever}^ part of the sun, are here shown as photographed during a 

 total eclipse. The upper figure presents a detail from the lower, greatly enlarged 

 From the Mount Wilson Observatory. 



ter by a variety of agencies. Hydrogen is present in all acids 

 and in most organic compounds. It also has the highest 



