1662 THE STORY OF THE UNIVERSE 



instruction to enable his faculties to begin their 

 work." In any case we may safely assume that man 

 must have begun his course in some one or more 

 of those portions of the earth which are genial in 

 climate, rich in natural fruits, and capable of yield- 

 ing the most abundant return to the very simplest 

 arts. It is under such conditions that the first es- 

 tablishment of the human race can be most easily 

 understood; nay, it is under such conditions only 

 that it is conceivable at all. And as these are the con- 

 ditions which would favor the first establishment 

 and the most rapid increase of man, so also are these 

 the conditions under which knowledge would most 

 rapidly accumulate, and the earliest possibilities of 

 material civilization would arise. 



Now what are the changes of external circumstance 

 which first, in the natural course of things, would 

 bring an adverse influence to bear upon mankind? 

 'Here again we are on firm ground, because we know 

 one great cause which has been always operating, and 

 we know its natural and inevitable effects. This 

 cause is simply the law of increase. It is the conse- 

 quence of that law that population is always pressing 

 upon the limits of subsistence. Hence the necessity of 

 migrations, and the force which has propelled suc- 

 cessive generations of men further and further, in 

 ever-widening circles round the original centre or 

 centres of their birth. Then, as it would always be 

 the weaker tribes who would be driven from the 

 ground which had become overstocked, and as the 

 lands to which they went forth were less and less 

 hospitable in climate and productions, the struggle 



