THE CONSERVATION OF FORCE 211 



ground, it produces an agitation, which is partly trans- 

 mitted to the vicinity as sound waves, and partly remains as 

 the motion of heat. The same result we must expect from 

 chemical action. When carbon and oxygen atoms have 

 rushed against each other, the newly-formed particles of 

 carbonic acid must be in the most violent molecular motion 

 that is, in the motion of heat. And this is so. A pound 

 of carbon burned with oxygen to form carbonic acid, gives 

 as much heat as is necessary to raise 80.9 pounds of water 

 from the freezing to the boiling point; and just as the same 

 amount of work is produced when a weight falls, whether 

 it falls slowly or fast, so also the same quantity of heat is 

 produced by the combustion of carbon, whether this is slow 

 or rapid, whether it takes place all at once, or by successive 

 stages. 



When the carbon is burned, we obtain in its stead, and in 

 that of the oxygen, the gaseous product of combustion car- 

 bonic acid. Immediately after combustion it is incandescent. 

 When it has afterwards imparted heat to the vicinity, we 

 have in the carbonic acid the entire quantity of carbon and 

 the entire quantity of oxygen, and also the force of affinity 

 quite as strong as before. But the action of the latter is 

 now limited to holding the atoms of carbon and oxygen 

 firmly united; they can no longer produce either heat or 

 work any more than a fallen weight can do work if it has 

 not been again raised by some extraneous force. When the 

 carbon has been burnt we take no further trouble to retain 

 the carbonic acid; it can do no more service, we endeavour 

 to get it out of the chimneys of our houses as fast as we 

 can. 



Is it possible, then, to tear asunder the particles of car- 

 bonic acid, and give to them once more the capacity of 

 work which they had before they were combined, just as 

 we can restore the potentiality of a weight by raising it from 

 the ground? It is indeed possible. We shall afterwards 

 see how it occurs in the life of plants; it can also be effected 

 by inorganic processes, though in roundabout ways, the 

 explanation of which would lead us too far from our present 

 course. 



This can, however, be easily and directly shown for an- 



