156 EVOLUTION OF THE EARTH 



that inherent ability is less important than the zeal and deter- 

 mination, or in other words, the energy with which that ability 

 is used. In our own experience have we not scores of times 

 had good ideas perhaps revolutionary ideas with which we 

 toyed for an hour or a day, only to forget them because we had 

 not the energy to undertake the hard work necessary to bring 

 them to fruition? Such energy is needed not only by the indi- 

 viduals of unusual capacity who make the great inventions, 

 but also by the people around them who must put the new 

 ideas into effect. "We have but partly solved the mysteries 

 of the progress of civilization, when we have pointed out 

 that each tangible stage of progress owed its initiative to a 

 new invention or discovery of science. To go to the root of 

 the matter we must needs explain how it came about that a 

 given generation of men was in a mental mood to receive the 

 new invention or discovery." 2 The necessary mental mood 

 is "alertness," which is merely a manifestation of energy. 

 Therefore it would seem that in the march of civilization 

 energy is quite as important as either inherent mental capacity 

 or material resources. Energy is partly the result of proper 

 food, clothing, and shelter, partly the result of inherited 

 ability, and partly the result of freedom from specific disease. 

 All these things depend in large measure upon climate. Back 

 of all, however, lies something else. Everyone knows that 

 he may be well fed, well dressed, well housed, of good ancestry, 

 and free from specific disease, and yet may not feel like work 

 even when he has no special occasion to be tired. Apparently 

 the thing that is needed is the stimulus of the right kind of 

 climate. Health is one thing; full efficiency is quite another. 



Effect of climate upon man's efficiency. This matter is so 

 important that we shall dwell on it at some length. Wherever 

 we find him, man seems to be characterized by a most delicate 

 physiological adjustment to climate quite apart from the innu- 



2 Williams, H. S., Article on "Civilization" in the "Encyclopaedia Britannica." 



