CHAPTER II 

 PLANTS AND ANIMALS 



While scientists believe implicitly in the conservation 

 of energy they recognize also the principle which is some- 

 times spoken of as "the degradation of energy." Ac- 

 cording to this teaching, though the. total quantity of 

 energy in the universe cannot grow less it can be indefi- 

 nitely dissipated. Thus our sun and the planets in 

 its system are losing heat into the depths of measure- 

 less space. The amount of energy in the earth is not a 

 constant, but a diminishing store. Since life as we now 

 know it is dependent upon the maintenance of a certain 

 temperature it cannot continue forever in a cooling 

 environment. 



Oxidation. Our world has an internal store of heat, 

 but this does not suffice to make its surface the abode of 

 many forms of life save as it is supplemented by the rays 

 of the sun. Wherever these fall daily from a considerable 

 elevation above the horizon the temperature favors living 

 organisms. But the service of the sun to the earth is 

 not limited to the retaining of its surface at a desirable 

 temperature level. The radiant energy is applied to the 

 formation of what we call the organic compounds and while 

 these exist it is held latent in them awaiting release. 



A very crude classification of the substances we find in 

 nature might be attempted by separating those which will 

 burn from those that will not. Many things will burn at 

 high temperatures which are not ordinarily thought of as 

 combustible. For example, this is true of iron. If we 

 restrict ourselves to the consideration of those things 

 which we regard as fuels and which burn easily we shall 

 be struck with the fact that they are products of past life, 



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