CHAPTER V 

 THE ATMOSPHEEE OF THE EAETH 



50. The Origin of the Atmosphere. As the earth cooled 

 down from the intensely hot condition which it is supposed 

 to have had at first, the substances which had not chem- 



BLUE HILL OBSERVATORY, MILTON, MASS. 



One of the first places in America where conditions of the upper atmosphere 



were studied. 



ically combined and formed liquids and solids, or which 

 required a low temperature for their consolidation were 

 left still in the gaseous state around the solid core. This 

 gaseous envelope composed of these substances sur- 

 rounding the earth we call the atmosphere. Some of 



110 



