CHEMICAL HISTORY OF A CANDLH 175 



five, six, or seven hours. What, then, must be the daily 

 amount of carbon going up into the air in the way of 

 carbonic acid I What a quantity of carbon must go from 

 each of us in respiration! What a wonderful change of 

 carbon must take place under these circumstances of com- 

 bustion or respiration! A man in twenty-four hours con- 

 verts as much as seven ounces of carbon into carbonic acid; 

 a milch cow will convert seventy ounces, and a horse seventy* 

 nine ounces, solely by the act of respiration. That is, the 

 horse in twenty-four hours burns seventy-nine ounces of 

 charcoal, or carbon, in his organs of respiration to supply 

 his natural warmth in that time. All the warm-blooded 

 animals get their warmth in this way, by the conversion of 

 carbon, not in a free state, but in a state of combination. 

 And what an extraordinary notion this gives us of the 

 alterations going on in our atmosphere. As much as 5,000,- 

 ooo pounds, or 548 tons, of carbonic acid is formed by res- 

 piration in London alone in twenty-four hours. And where 

 does all this go? Up into the air. If the carbon had been 

 like the lead which I showed you, or the iron which, in 

 burning, produces a solid substance, what would happen? 

 Combustion could not go on. As charcoal burns it becomes 

 a vapor and passes off into the atmosphere, which is the 

 great vehicle, the great carrier for conveying it away to 

 other places. Then what becomes of it? Wonderful is it 

 to find that the change produced by respiration, which 

 seems so injurious to us (for we can not breathe air twice 

 over), is the very life and support of plants and vegetables 

 that grow upon the surface of the earth. It is the same 

 also under the surface, in the great bodies of water; for 

 fishes and other animals respire upon the same principle, 

 though not exactly by contact with the open air. 



Such fish as I have here [pointing to a globe of gold-fish] 

 respire by the oxygen which is dissolved from the air by the 

 water, and form carbonic acid, and they all move about 

 to produce the one great work of making the animal and 

 vegetable kingdoms subservient to each other. And all the 

 plants growing upon the surface of the earth, like that 

 which I have brought here to serve as an illustration, absorb 

 carbon; these leaves are taking up their carbon from the 



