M. Dumas on the Chemical Statics of Organized Beings. 345 



of oxide of ammonium and of nitric acid, which can only have 

 a momentary existence in the air because of their solubility in 

 water. 



The air, then, is constituted of a mixture of oxygen, azote, 

 carbonic acid, and marsh gas. 



The carbonic acid in it varies, and indeed greatly, since 

 the differences in it extend almost from the simple to the 

 double, from 4 to 6-10,000ths. May [not this be a proof that 

 plants take from the air this carbonic acid, and that animals 

 take back a part from it? in a word, may this not be a proof 

 of thart equilibrium of the elements of the air attributed to the 

 inverse actions which animals and plants produce upon it ? 



It has, indeed, been long since remarked ; animals borrow 

 from the air its oxygen, and give to it carbonic acid ; plants, 

 in their turn, decompose this carbonic acid in order to fix its 

 carbon and restore its oxygen to the air. 



As animals breathe continually; as plants breathe under the 

 solar influence only ; as in winter the earth is stript, whilst in 

 summer it is covered with verdure ; it has been supposed that 

 the air must transfer all these influences into its constitution. 



Carbonic acid should augment by night "and diminish by 

 day. Oxygen, in its turn, .should follow an inverse progress. 



Carbonic acid should also follow the course of the seasons, 

 and oxygen obey the same law. 



All this is true, without doubt, and quite perceptible as to a 

 portion of air limited and confined under ajar; but in the mass 

 of the atmosphere, all these local variations blend and disap- 

 pear. Accumulated centuries are requisite in order effectually 

 to put in action this balance of the two kingdoms, with regard 

 to the composition of air; we are then very far from those 

 daily or yearly variations, which we had been apt to look 

 upon as befcg as easy to observe as to foresee. 



With regard to oxygen, calculation shows that, exaggera- 

 ting all the data, not less than 800,000 years would be required 

 for the animals living on the surface of the earth to consume 

 it entirely. 



Consequently, if we suppose that an analysis of the air had 

 been made in 1800, and that during the entire century plants 

 had ceased to perform their functions on the surface of the 

 whole globe, the animals at the same time all continuing to 

 live, the analysts in 1900 would find the oxygen of the air 

 diminished by l-8000th of its weight, a quantity which is be- 

 yond the reach of our most delicate methods of observation, 

 and which, assuredly, would have no influence whatever on 

 the life of animals or plants. 



As to this, then, we cannot be deceived; the oxygen of the 



