DESIGN IN NATURE 275 



ture, but also the existence of an atmosphere and of 

 a large quantity of water on the earth. 



In addition to these things, the fact that water 

 expands on cooling from 4° Centigrade until it 

 reaches 0° and freezes, thus rendering the ice con- 

 siderably lighter than the water, so that it floats on 

 the surface, is a matter of much importance. If, 

 instead of expanding when it freezes, it were to fol- 

 low the almost universal law and contract on cooling 

 to the freezing point, the ice formed would be heavier 

 than water and would sink to the bottom of rivers 

 and lakes, thus causing it to accumulate in much 

 larger quantities than at present; so much would 

 probably be formed, owing to the fact that the sur- 

 face water would not be protected by ice as it now is, 

 that it would probably destroy all life, at least in the 

 fresh waters of the globe. 



These large provisions in nature, adapting the 

 earth to the existence of a countless number of or- 

 ganic forms, we cannot regard as having been pro- 

 duced by chance. 



The distance of the earth from the sun is such as 

 to give a temperature favorable to life. If ether 

 exists, its resistance to the progress of the earth in its 

 orbit is causing the earth to slowly approach the sun 

 in a spiral orbit, and this gradual approach may pos- 

 sibly compensate for a decrease in the radiant energy 

 of the sun. 



The length of days and nights on most parts of the 

 earth is of great importance in helping to preserve a 

 uniform temperature which favors the existence of 

 living organisms. If the days and nights were much 

 lengthened, it is evident that this would produce 

 much greater extremes of temperature than at pres- 

 ent. 



The fact, also, that the northern hemisphere of the 



