THE BALANCE OF NATURE. 165 



the earth's surface, and causes vapor to pass off 

 from the water surfaces into the atmosphere. 



Another part of the solar energy or heat is 

 directly expended in maintaining one or another 

 of the myriad forms of plant and animal life. 



If any of the five great geographical forms ap- 

 propriates more than its share of the solar energy, 

 a disturbance of the balance of nature is effected, 

 which may produce far-reaching changes in the 

 operation of the entire mechanism. 



Let us inquire as to some of the more evident 

 ways in which this balance of nature is preserved, 

 how it may be disturbed, and some of the effects 

 produced by such disturbances. 



We will discuss this influence from the stand- 

 point of the five great geographical forms, 

 namely, the land, the water, the air, plants, and 

 animals. 



The Land and Water. An exact balance, both 

 in the amount and distribution, of the land and 

 water areas of the earth is absolutely necessary for 

 the existence of the earth's present plant and ani- 

 mal life. 



The total water areas of the earth are in excess 

 of the land areas in about the proportion of 2J- 

 tol. 



