THE CONQUEST OF NATURE 



between a weight and the earth, and thus enables a 

 man or a woman to convey a load that would be far 

 beyond his or her unaided powers. It is well to use 

 both genders in this illustration, since among primitive 

 peoples it is usually the woman who is the bearer of 

 burdens. And indeed to this day one may see the 

 women of Italy and Germany bearing large burdens 

 on their backs and heads, and dragging carts about the 

 streets, quite after the primitive method. 



The more one considers the mechanism, the more 

 one must marvel at the ingenuity of the pre-historic 

 man who invented the wheel and axle. Its utility 

 is sufficiently obvious once the thing has been done. 

 In point of fact, it so enormously reduces the friction 

 that a man may convey ten times the burden with its 

 aid that he can without it. But how was the primitive 

 man, with his small knowledge of mechanics, to predict 

 such a result? In point of fact, of course, he made 

 no such prediction. Doubtless his attention was 

 first called to the utility of rolling bodies by a chance 

 observation of dragging a burden along a pebbly beach, 

 or over rolling stones. The observation of logs or 

 round stones rolling down a hill might also have stimu- 

 lated the imagination of some inventive genius. 



Probably logs placed beneath heavy weights, such 

 as are still employed sometimes in moving houses, were 

 utilized now and again for many generations before 

 the idea of a narrow section of a log adjusted on an 

 axis was evolved. But be that as it may, this idea was 

 put into practise before the historic period begins, and 

 we find the earliest civilized races of which we have 



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