274 ORGANIC EVOLUTION CONSIDERED 



ture to which different parts of the universe are sub- 

 jected — the almost absolute zero of interstellar space, 

 the frigid moon, the sun with a temperature of thous- 

 ands of degrees — and when we remember that a 

 change of temperature of comparatively few degrees 

 would destroy all known forms of life, and that for 

 many millions of years the earth's temperature has 

 been so uniform that life has existed in abundance, 

 nothing short of intelligent purpose can explain these 

 facts. Even if we accept the theory that the sun's 

 heat has been generated by the bombardment of me- 

 teors, which is, indeed, the most plausible physical 

 theory, yet it would seem to require Divine intelli- 

 gence and power to keep the supply uniform. 



In addition to the quite uniform temperature of 

 the sun during this long period, certain conditions 

 were necessary upon the earth in order to prevent its 

 temperature from undergoing much greater variation 

 than has taken place. The existence of the atmos- 

 phere around the earth and of moisture in the atmos- 

 phere is of the greatest importance in retaining the 

 heat of the sun which has reached the surface of the 

 earth. The rays of heat of high refrangibility readily 

 pass through the atmosphere to the earth, but on 

 striking the earth they are changed to rays of low 

 refrangibility, which do not readily escape through 

 the atmosphere into space. 



Also, the large quantity of water upon the surface 

 of the earth has much to do in rendering the climate 

 uniform. The high specific heat of water enables it 

 to absorb a large quantity of heat without undergoing 

 much change of temperature, and this heat is slowly 

 given up by the water to render the climate more 

 uniform. 



The production of a uniform climate through long 

 periods involved not only a sun of uniform tempera- 



