ON THE CONSERVATION OF FORCE 219 



interchanges between various inorganic natural forces work- 

 ing force may indeed disappear in one form, but then it 

 reappears in exactly equivalent quantity in some other form ; 

 it is thus neither increased nor diminished, but always 

 remains in exactly the same quantity. We shall subsequently 

 see that the same law holds good also for processes in 

 organic nature, so far as the facts have been tested. 



It follows thence that the total quantity of all the forces 

 capable of work in the whole universe remains eternal and 

 unchanged throughout all their changes. All change in 

 nature amounts to this, that force can change its form and 

 locality without its quantity being changed. The universe 

 possesses, once for all, a store of force which is not altered 

 by any change of phenomena, can neither be increased nor 

 diminished, and which maintains any change which takes 

 place on it. 



You see how, starting from considerations based on the 

 immediate practical interests of technical work, we have 

 been led up to a universal natural law, which, as far as all 

 previous experience extends, rules and embraces all natural 

 processes; which is no longer restricted to the practical 

 objects of human utility, but expresses a perfectly general 

 and particularly characteristic property of all natural forces, 

 and which, as regards generality, is to be placed by the side 

 of the laws of the unalterability of mass, and the unaltera- 

 bility of the chemical elements. 



At the same time, it also decides a great practical question 

 which has been much discussed in the last two centuries, to 

 the decision of which an infinity of experiments has been 

 made and an infinity of apparatus constructed that is, the 

 question of the possibility of a perpetual motion. By this 

 was understood a machine which was to work continuously 

 without the aid of any external driving force. The solution 

 of this problem promised enormous gains. Such a machine 

 would have had all the advantages of steam without 

 requiring the expenditure of fuel. Work is wealth. A( 

 machine which could produce work from nothing was as 

 good as one which made gold. This problem had thus for 

 a long time occupied the place of gold making, and had 

 confused many a pondering brain. That a perpetual motion 



