blood itself, whatever has formed a part of the organized body, now dead, and repassing through the process of decomposition, back to the simple physical elements, all its forms of beauty gone, and exhaling only matters highly deleterious to animal life, mixed with the soil, are recombined into new products, spring up into new plants, and thus re-appear under new forms of beauty, and afford fresh nutriment to myriads of animals. The very refuse of the matters which have served as food and clothing to the inhabitants of the crowded city, and which, allowed to accumulate there, taint the air, and render it pestilential, promptly removed, and spread out on the surface of the surrounding country, give it healthfulness, clothe it with verdure, and endow it with inexhaustible fertility. 854. The quantity of matter excreted by the plant is proportionate to the energy of its vital actions. Hence it is always greatest in spring, when the tender leaves are beginning to shoot; gradually diminishes as autumn approaches; and, at last, as the leaves turn yellow, and the vessels which connect the leaves with the stalk dry up and are closed, it almost wholly ceases. 855. It is copious in proportion to the number of the leaves, and to the extent of the surface they present. From experiments performed as long ago as the year 1699, by Woodward, it appears that, of the whole quantity of water absorbed by the plant, the least proportion exhaled to that retained is as 46 or 50 to 1; in many cases it is as 100 or 200 to 1, and in some above 700 to 1. In one experiment, a plant which imbibed 2501 grains of water, increased in weight only three grains and a half: hence the dampness and humidity of the air in all places in which trees and the larger vegetables abound; more especially when the leaves are young, and most numerous and active; and hence also the magnitude of the rivers in all extensive countries which are covered with forests. 856. Exhalation, scarcely appreciable in the night, is most abundant during the day under the influence of the solar light. If two plants of the same size are covered with two glass bells, and one be exposed to the sun’s light, while the other is left in the shade, the inner surface of the former bell becomes covered with drops of water, while that of the second remains perfectly dry.