j 50 ELEMENTARY SCIENCE 



empty spaces through which earth and the other heavenly 

 bodies move in their orbits. 



Relations Between Atmosphere and Heat. Now the 



thing for us to do is to consider this atmosphere, and the 

 substances which are in it, and then to see what effect it 

 must necessarily produce upon the distribution of the heat 

 which comes from the sun. Then we shall perceive that, 

 like soil and water and light and heat itself, the atmosphere, 

 through its effects on heat, as well as through its supply 

 to us of the air we breathe, is one of these great facts of 

 nature which has determined and continues to determine 

 the nature of life. We shall see how small we seem to 

 be as compared with these enormous facts and forces of 

 nature which permit us to exist. We shall also see that 

 the atmosphere through the effects which heat produces 

 upon it is the chief thing which determines the distribu- 

 tion of water; similarly, through the effects which it pro- 

 duces upon heat it is a very important factor in the forma- 

 tion of soil. Soil formation and water distribution are, 

 of course, two of the things upon which life depends. 

 Thus, more and more, we come to realize that heat and 

 the atmosphere are two great co-operating agencies whose 

 relations determine the nature of our lives. Surely it is im- 

 portant that we should have some understanding of the 

 relations which exist between them. 



Let us remember also that air is below us as well as 

 above us. It penetrates the soil and the rocks, it affects 

 fertility, and the substances which compose it become 

 dissolved in water and unite chemically with rock, an 

 action similar to that which occurs when, through respira- 

 tion, oxygen unites with substances in living bodies. 



