AGRICULTURE WITH CHEMISTRY. 10

By heat is to be understood the sensation arising”

from the solar rays, or from the combustion of inflam- mable bodies. Combustion cannot take place without the presence of air, and it is only the vital part of air that promotes this process. A certain degree of heat is requisite for animal and vegetable life. It is generated in animals, in consequence of respiration, by the ab- sorption of the vital part of atmospheric air, and com- bination thereof with the animal system; here called the process of animaloxygenation: and as animals have thus the power of generating heat by respiration, they can

live in a much greater degree of cold than vegetables.

To the presence of heat is to be ascribed the fluidi of water; to the absence of it, its solidity, or the forma-

tion of ice. The principle of heat is contained in bodies without

C2 heat.

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