VEGETATION AND THE ATMOSPHERE. 
BY J. JAMIN. 
TRANSLATED FOR THE SMITHSONIAN INSTITUTION FROM THE ‘REVUE DES DEUX MONDES.” 
Persons who are not devoted to the physical sciences will, perhaps, pardon 
me if I take the liberty of recalling to them that the air in the midst of which 
animals and plants live is a mixture of two very different gases. ‘I'he one, 
almost inert and without appreciable influence in the phenomena of nature, is 
called azote; the other, on the contrary, possesses the most active properties 
and performs the most important part in the support of life on the globe; this 
is oxygen. Among other properties it possesses that of uniting with carbon 
or charcoal, and while this union, or, to apply the scientific term, this combi- 
nation is taking place a considerable quantity of heat and light is disengaged. 
The carbon is said to burn, and it was thought at first, without reflection, to 
be annihilated; it is, however, merely. transformed into a gas which mingles 
with the atmosphere, from which the chemist can recover not only all the car- 
bon which has been burned, but all the oxygen which united with it. In order 
to recall to the memory the origin and composition of this compound gas it 
has received the name of carbonic acid. 
Wood, which is essentially composed of carbon and water, burns in the same 
manner as carbon, expelling the water in the form of vapor and transforming 
the carbon, by its union with the oxygen of the air, into carbonic acid. Fruit, 
herbs, bread, and all our aliments, having a chemical composition analogous to 
that of wood, may, like it, be burned in a furnace, and Lavoisier has taught us 
that the substance of these aliments undergo a real but slow combustion in the 
respiratory system of the animals which eat them. Every animal is therefore 
a furnace, every aliment a combustible; the oxygen of the air is absorbed in 
respiration, is replaced by carbonic acid, and the water ejected by the natural 
outiets or by exhalation. 
Since carbonic acid is necessarily produced by animal life it must form an 
integral part of our atmosphere. Chemists, in effect, detect it there, but in the 
‘minute proportion of four or five parts of the acid in ten thousand of air. It is 
a gas which can neither support life nor combustion, since it is, on the contrary, 
the product of these processes. Hence all animals confined under glass bells, 
‘ filled with air, rapidly exhaust the oxygen, replace it by carbonic acid, and 
soon die, not from a poisonous effect of the gas, but from a want of respiratory 
sustenance. 
Having recalled these facts, I shall describe a celebrated experiment which 
vegetables themselves are continually performing in our midst without our 
having consciousness of it, though it is accomplished on an immense scale, and 
may be justly considered one of the most essential phenomena of the world; 
an experiment, moreover, so simple that any one may repeat it at pleasure. In 
order to success, it is necessary to take a healthy and fresh branch, in full 
foliage, of one of those aquatic plants which grow immersed in ponds or rivers ; 
introduce it into a glass jar, which is then filled with spring water, or, still 
better, with what is called mineral water, which contains, as we know, a large 
proportion of free carbonic acid; having closed the mouth of the jar when 
