ON THE CONSERVATION OF FORCE. 351 



coal is the chemical union of carbon with the oxygen of 

 the air, taking place under the influence of the chemical 

 affinity of the two substances. 



We may regard this force as an attractive force between 

 the two, which, however, only acts through them with 

 extraordinary power, if the smallest particles of the two 

 substances are in closest proximity to each other. In 

 combustion this force acts ; the carbon and oxygen atoms 

 strike against each other and adhere firmly, inasmuch as 

 they form a new compound — carbonic acid — a gas knowm 

 to all of you as that which ascends from all fermenting 

 and fermented liquids — from beer and champagne. Now 

 this attraction between the atoms of carbon and of oxygen 

 performs work just as much as that which the earth in the 

 form of gravity exerts upon a raised weight. When the 

 weight falls to the ground, it produces an agitation, which 

 is partly transmitted 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 

 carbonic acid. Immediately after combustion it is in- 

 candescent. When it has afterwards imparted heat to the 

 vicinity, we have in the carbonic acid the entire quantity 



