55o THE POPULAR SCIENCE MONTHLY 



who have longest been subjected to the urgent necessity to labor. It 

 is, accordingly, largely a matter of climate; and we find that, in gen- 

 eral, the instinct to work diminishes from high latitudes to the tropics. 

 This aspect of work appears as a substantially modern conception. In 

 order to appreciate the full significance of the point of view, it will be 

 helpful to turn our attention for a while to an entirely different field; 

 that of physical science. There, the idea of work (and of its correlate, 

 energy) has begun to play a role so prominent as to be in fact the 

 center and point of departure of our apprehension of life and of the 

 universe. 



In the narrowest physical sense, "work" is exclusively mechanical 

 work, such as that required to move an object. Such work is performed 

 when a locomotive pulls a train or when a man lifts a load. In these 

 cases the work is made up of two factors, first, power or force ; second, 

 path or distance. The science of physics teaches us that the work is 

 equal to the power (or force) multiplied by the path (or distance), be- 

 cause the product has the peculiarity that it is equally influenced by a 

 change in either component. If either the force or the distance be 

 doubled, the work will also be doubled. In virtue of measuring work 

 in this precise manner, a very important law of nature is arrived at, 

 called the law of the conservation of work, or energy. The essence of 

 the law is, that by no means is it possible to obtain work out of nothing, 

 but only to obtain one kind of work out of another kind of work, under 

 the limitation that the total work obtained can never be greater than 

 that used to start with. 



According to a familiar anecdote, Archimedes declared that if he had 

 a lever long enough and a place to rest it on, he could move the world. 

 He figured that he could increase the force of his effort indefinitely by 

 indefinitely increasing the length of the lever. Every laborer who uses 

 a crow-bar has experimental knowledge of the effect, which, at first 

 glance, seems incompatible with the conservation law. The apparent 

 discrepancy vanishes when we remember that the short arm of the 

 lever moves less than the actuating hand, so that just in proportion as 

 we increase the force do we diminish the distance through which the 

 force is applied; the work done at the short end of the lever remaining 

 the same as that performed by the hand at the long end. Hence, while 

 Archimedes might indeed move the world as he imagined, yet the dis- 

 tance through which it moved would be so infinitesimal as to transcend 

 observation. 



In a word, we may say that work is not creatable. We must be con- 

 tent with that which is in the world accessible to us. Still, our whole 

 existence depends on work, in the broader sense. Whenever anything 

 whatever happens, work is consumed, to be transformed into that which 

 distinguishes the new from the old condition. The significance of 



