128 ANNUAL OF SCIENTIFIC DISCOVERY. 



has been effected, provided that other actions are not at the same time 

 brought into play. If, however, mechanical work is at the same time ac- 

 complished, as in the case of the steam engine, we obtain as much less heat 

 as is equivalent to this work. The quantity of work produced by chemical 

 force is in general very great. A pound of the purest coal gives, when 

 burnt, sufficient heat to raise the temperature of 8,086 pounds of water one 

 degree of the centigrade thermometer ; from this we can calculate that the 

 magnitude of the chemical force of attraction between the particles of a 

 pound of coal and the quantity of oxygen that corresponds to it, is capable 

 of lifting a weight of one hundred pounds to a height of twenty miles. 

 Unfortunately, in our steam engines, we have hitherto been able to gain only 

 the smallest portion of this work ; the greater part is lost in the shape of 

 heat. The best expansive engines give back as mechanical work only eigh- 

 teen per cent, of the heat generated by the fuel. 



From a similar investigation of all the other known physical and chemi- 

 cal processes, we arrive at the conclusion that Nature as a whole possesses a 

 store of force which cannot in any Avay be either increased or diminished, 

 and that, therefore, the quantity of force in nature is just as eternal and un- 

 alterable as the quantity of matter. Expressed in this form, I have named 

 the general law " The Principle of the Conservation of Force." 



"We cannot create mechanical force, but we may help ourselves from the 

 general store-house of Nature. The brook and the wind, which drive our 

 mills, the forest and the coal-bed, which supply our steam engines and warm 

 our rooms, are to us the bearers of a small portion of the great natural sup- 

 ply which we draw upon for our purposes, and the actions of which we can 

 apply as we think fit. The possessor of a mill claims the gravity of the de- 

 scending rivulet, or the living force of the moving wind, as his possession. 

 These portions of the store of Nature are what give his property its chief 

 value. 



Further, from the fact that no portion of force can be absolutely lost, it 

 does not follow that a portion may not be inapplicable to human purposes. 

 In this respect the inferences drawn by William Thomson from the law of 

 Carnot are of importance. This law, which was discovered by Garnet 

 during his endeavors to ascertain the relations between heat and mechanical 

 force, which, however, by no means belongs to the necessary consequences 

 of the conservation of force, and which Clausius was the first to modify in 

 such a manner that it no longer contradicted the above general law, ex- 

 presses a certain relation between the compressibility, the capacity for heat, 

 and the expansion by heat of all bodies. It is not yet considered as actually 

 proved, but some remarkable deductions having been drawn from it, and 

 afterwards proved to be facts by experiment, it has attained thereby a great 

 degree of probability. Besides the mathematical form in which the law was 

 first expressed by Carnot, we can give it the following more general expres- 

 sion : " Only when heat passes from a warmer to a colder body, and even 

 then only partially, can it be converted into mechanical work." 



The heat of a body which we cannot cool further, cannot be changed into 

 another form of force ; into the electric or chemical force, for example. 



