1297. The writings of Liebig, which were first published to the world in 1840, at length afforded a better method of reconciling practice with theory. The important fact that plants derive the greater portion of even their carbon from the air explained the reason why it was necessary to turn over stable manure frequently while it was undergoing the progress of decay, as it is found that this process makes it imbibe from the air those gases which are most wholesome to plants, while the burning ammoniacal gases are so mellowed down, by combination with carbonic acid and other substances, as to be no longer injurious, but, on the contrary, become most important constituents of the manure.
