Science of Farmers. 515 
did.* The charcoal consists of carbon, with a slight admixture 
only of earthly and saline matter which remains behind when the 
coal or carbon is burned in the open air. When the charcoal or 
carbon is burned in the open air, it combines with the oxygen of 
the air to keep up the combustion, and the whole of the coal en- 
ters into a chemical union with the oxygen, and forms carbonic 
acid, or in other words carbonic acid consists of oxygen, with a 
definite and fixed quantity of charcoal or carbon dissolved in it. 
This gas is composed of two proportions of oxygen and one of 
carbon. In this state it is taken in by the leaves of plants. The 
leaves of plants are their lungs, and they possess the power of ab- 
sorbing from the air, carbonic acid, and in day light it is decom- 
posed, but much more rapidly in clear sun light. When thus de- 
composed in the leaf, the oxygen is set free, and is again restored 
to the atmosphere, the carbon is retained and mingled with the 
true sap of the plant, and in obedience to those mysterious laws 
of chemical combinations, is made to form a moiety of the endless 
variety of wood, fruits, seeds, &c., &c., which are the results of 
vegetable life. 
It may seem a mystery, how the leaf of a plant can take from 
the air the carbonic acid, when in such apparent small quantity, 
and separate the carbon from its oxygen. We grant it is a mys- 
tery; but then we know for a certainty the fact of the leaves of 
plants possessing this power of absorption and decomposition; 
it is the way the growth of a plant has been provided for; the 
Creator has so willed it. 
Plants take from the atmosphere by their leaves, carbonic acid, 
a deleterious gas, and decompose it and restore to it the oxygen; 
that is taken into the lungs of animals, combines with the carbon 
of the food, and by the process of respiration is given off to the 
atmosphere in the form of carbonic acid, the food of plants. 
It is sometimes said, that politicians and gamblers play into 
each other's hands for their own private good. Animals and 
plants perform a more honorable operation; they play into each 
other's mouths for the general good. 
It is no more mysterious how this invisible elastic gas can be 
converted into wood, or other solid substances, than are many 
other of its wonderful and well known combinations. 
Every 100 lbs, of pure marble or limestone, as taken from the 
quarry, contains in round numbers 44 lbs. of this very gas. By 
subjecting the marble to a lonsj continued red heat, this gas is 
driven off, and leaves but 56 lbs. of lime. 
In this place, there is a pearl-ash factory. In every 100 lbs. of 
pearl-ash, the manufacturer sends to Boston, (the place of sale,) 
there is 32 lbs. of this gas, combined with 68 lbs. of caustic pot 
• The moisture, or w.iter in wood, or other vegetable productions, is not the 
solid part; potatoes when sliced and dried, loie 70 to 80 per cent of water. 
