We have then three great natural divisions of the ingredients of soil: 1, geine, 2, salts, 3, granitic sand, or silicates. Let us glance at these three divisions:

1. Geine.-Geine enters vegetables either as geine or as an alkaline, earthy or metallic geate dissolved in water or alkali. The acids and salts of the plant decompose these varied forms. The elements of geine, its oxygen, hydrogen, and carbon, play their usual parts in vegetable economy. The earthy and alkaline bases of the geates form the bases of the various salts which plants afford.

2. Salts. This class includes, first, compounds of geine, second, alkaline, salts, potash, soda, ammonia, and all their combinations known by the names of carbonates, sulphates, phosphates, nitrates, muriates, &c.

3. Silicates, or granitic sand.

TABLE of the constituents of the elements of granitic sand.

Argillite, a soft rock of the consistence of common slate, contains carbon. Sulphuret of iron abounds. Its decomposition produces with the silicates, sulphates of alkalies, earths, and oxyds. These with the muriates and phosphates, give the inorganic elements of plants. Burning reduces these to two classes, ashes and soluble salts. The last are found in soot. The ashes are formed of salts and silicates as the following analysis shews:

Analysis of Wood Ashes.

Ashes are divided by the simple process of leech

ing, into two parts, soluble and insoluble in water. The average quantity of ashes from 100 parts of dry oak, beech, birch, &c. is, 2.87.

The composition of the insoluble part of ashes gives us nearly the constituents of leeched ashes. The soap boiler's process, however, always leaves a portion of potash combined with silica, and he adds more or less lime to render the lye caustic. These add to the value of leeched ashes something more than is indicated in the table. Exposure to air, and the galvanic operations of the roots of plants decompose this silicate of potash, (crude glass,) and render the potash soluble in water. This is one great source of the active power of leeched ashes. The course of this wonderful power, not only in fresh and in leeched ashes, but in some degree, in all salts, is to be found in the action of the bases of these salts on geine and on silicates or granitic sand.

Peat ashes abounds in carbonate, sulphate, and especially in phosphate of lime. I have always traced free alkali in peat ashes. But alkali exists in it rather as a silicate, as in leeched ashes. Anthracite coal ashes contain carbonate of lime, alumina, oxyd of iron, and, as more or less wood or charcoal is used in kindling it, some potash also-it is good so far as these abound.

"There is one great, simple principle running through all the classes of soils. It is this, that in all

salts and silicates the action of the base is ever the same in vegetation. The base of the silicates and salts acts always in one uniform mode. Peculiarities of action depend on the acid constituent of the salt. Lime, for instance, acts ever the same, whether it is used as carbonate, sulphate, or phosphate, marl, plaster, or bone-dust. The salt is decomposed by the living plant. The various acids combine with the alkalies, as they are eliminated, from the decomposition of the silicates, and the lime, liberated, acts ever as lime. It acts in its caustic state, as a converter of insoluble into soluble geine. If this does not exist in the soil, all the lime in the world would not cause plants to grow. The base of the lime-salts acts primarily on geine, either solving the soluble or converting the insoluble. The same is true of alumina, iron and the bases of all salts. The same general rule applies to all alkaline, earthy or metallic salts and to silicates.

"The order in which the farmer may apply salts is the following: Carbonate, phosphate, and sulphate of lime, carbonates, nitrates, muriates, and sulphates of alkalies. No salts, excepting carbonates, can be used in large quantities. The reason is at once explained by the principle of unity of action of the bases. The acid of the salts, eliminated, decomposes the geates, rendering the soluble insoluble, the acid combines with any free base, produced from the decomposition of the silicates, and thus prevents that forming soluble geine. Having saturated the bases, any excess acts then as free acid, poisoning the vegetable, as oil of vitriol, or muriatic acid would animals. In carbonates, the acid forms part of the food of plants. The alkaline geates are so very soluble, that when alkalies, as ashes for instance, are freely used, we lose a part, by its draining away, or in wet soils becoming too dilute. But a small dose produces all the beneficial effects of a large dose of lime. We have in ashes, not only the alkali to solve geates, but a very large portion of carbonate and phosphate

of lime. Experiments are wanting to prove the relative value of lime and ashes. I should not deem it extravagant to say, that a bushel of ashes is equal to a cask of lime. The alkalies and their salts act more powerfully than any other substance, in solving and converting geine. Lime in all its forms ranks next. These produce always decided beneficial effects. The alkalies never fail. Ashes show their effects at once, due to the alkaline part, while their carbonate of lime produces more permanent effect. Lime, from peculiar states of the soil, may not show any immediate good result, but ultimately, this result is sure to follow. Permanent barrenness never is produced by the free use of carbonates. It surely follows the free use of all other salts, yet in small doses, they all and ever act beneficially, whenever their bases, combined with carbonic acid, would be beneficial.

"But how do the elements of soil act? As I have stated in the report of Professor Hitchcock, by forming galvanic batteries with the roots of living plants. The most active element in the pile is the root. The soil, like the rocks from which it is derived, is slowly acted on by atmospheric agents. The effect of this action annually is imperceptible.

"A single plant in one season will effect a greater amount of decomposition of a given portion of soil, than that produced by all the atmospheric agents in many years. The galvanic agency of plants is not confined to the soil, in immediate contact with their roots. It extends from these, in every direction, to undetermined distances. Hence there is a transfer, as is usual in galvanic decompositions, of substances quite remote from the plant. The whole plant contributes to this galvanic agency. It never exists in full force, perhaps not at all, till the plant has pushed above ground-acted on by air and light.

"The soil, as we have explained, consists almost wholly of silicates, though it has been proved, that carbonic acid slowly decomposes these, and an argu