useful, in reference to animal life. Were this arrangement perfect, there would remain nothing for man to do as a cultivator of the soil; but, although the general tendency is clearly towards perfection, yet in this, as well as in other particulars, there is obvious and intentional imperfection mingled with it. It is, without doubt, part of the plan of Creative Intelligence, that the arrangement should be so left as to admit of the beneficial interference of man, and to enable him to adapt it to his own advantage and convenience. This is true both with regard to the nature of the soil, and the properties of plants; and it will now be my pleasing task to point out some of the qualities and adaptations, by which the former invites and rewards cultivation, and the latter, under the care and skill of rational beings, are rendered more subservient to use or enjoyment.

1. With regard to soil. The surface of the earth is composed of ingredients which are more or less prolific, according to their nature, and the proportions in which they are intermixed. There is, first of all, simple earth, a substance which, when analyzed, is found to be nothing more than abraded and disintegrated rock. It is not of itself prolific, or, at least, is so only in a very slight degree, and indeed is considered by most physiologists as of no other use to plants than that of supporting them, or furnishing a medium by which they may fix themselves to the globe. Some earthy ingredients, indeed, are found in all plants, but they undergo no chemical change, and cannot properly be said to be the food of vegetables. The true nourishment of plants is water and decomposing organic matter, and these must be mixed in certain proportions with pure earth, so as to constitute soil. This is one principle on which the power of man, in rendering the soil fertile, is found to rest. He may by various processes-by mixing, for instance, with the land, some vegetable or animal matter in a state of decay, where this constituent is deficient, or by adding earthy materials where this happens to be redundant; by loosening it with agricultural instruments, and thus subjecting it to the influence of water, when its indurated state prevents that

VIII.

necessary element from penetrating; or by draining it, and thus withdrawing a superabundant supply of moisture ;-by any one of these means he may ameliorate the soil, and render it fertile, when it would otherwise be barren, or increase its prolific qualities when they do not yield a sufficient return.

Again, the mere mixture of ingredients already existing in a soil, and exposure to the atmosphere, are found to produce a beneficial result, by promoting fermentation, and by subjecting them to the influences of the sun and the air. Here, again, man has the means of increasing the prolific quality of the soil, and of rendering it more fit for his use.

These, and various other operations, are rendered important by the actual state of soils over the surface of the earth. In a great majority of instances, the land is not in such a highly prolific state as to be incapable of improvement by judicious management; and even where it is composed of ingredients mingled in the greatest perfection, and in the most beneficial proportions, it becomes deteriorated by use, so as to require constant attention. Such an arrangement is best fitted for the present condition of the human race. There is here something calculated to stimulate industry and ingenuity, by holding out the prospect of advantage.

Nor must it be forgotten, that the various materials necessary for the amelioration of the soil, are very generally within reach; and that the operations by which these materials may be rendered available, are in themselves sufficiently simple, and require instruments by no means complicated. Were it otherwise, the condition would be unsuitable to the circumstances of man, except when considerably advanced in civilization; and obstacles would be interposed at the very outset, which might prove fatal to his improvement, not only in this, but in other respects. Let us suppose, for a moment, what would be the consequence to agricultural progress in its earlier stages, if the only method of improving the soil were by excavating manure, for example, from the hard rock, as is the case in the application of lime, and causing it to undergo decomposition by fire. Such an operation would

obviously be too recondite to be discovered by man in an uncivilized state, and too difficult and complicated to be generally reduced to practice. But the ordinary means by which the soil is improved, are readily at hand, and are too obvious not to be discovered in the natural course of things, without scientific knowledge, or more skill than is acquired by man in a very early stage of society. As soon as he has begun to turn up the earth, he discovers that the vegetables, with which its surface was covered, fertilize the soil as they decay; the dung, accidentally dropped, he observes to give peculiar vigor to the vegetation in those places where it has been covered in; the land he finds to be better adapted to the growth of plants, when cleaned of weeds and pulverized; too much and too little moisture he discovers to be equally injurious. It is thus, that, in a short time, and with the simple exercise of a little observation, the great and leading principles of agriculture are unfolded, and the soil yields its powers to man without the aid of science.

The importance of all this facility will appear more clearly, when we consider how much of human improvement and happiness depends on the resources of agriculture. It is from this employment, indeed, that the advancement of society in the arts and sciences, may be considered as mainly taking its origin. While men gain their subsistence by hunting or fishing, they are always in a savage state, having seldom any fixed habitations, but roaming through the forests, or frequenting the seacoasts or the banks of rivers, wherever their means of subsistence in the various seasons of the year may be found most abundant. The shepherd state, indeed, implies considerable advancement beyond that which we have mentioned. It supposes the recognition of personal property, and sometimes also, but by no means generally, a settlement in a particular locality, and the possession of a few domestic comforts. But it is not till man has advanced a step further, and has begun to cultivate the soil, that he makes any very important progress in civilization, or becomes bound permanently with his fellows in the bands of a well-organized community. It may, there

fore, be regarded as a proof of wise and beneficent arrangement, not only that the soil requires and rewards cultivation, but also that the means by which that cultivation may be effected are so easy of access, and so apparent to general observation.

NINTH WEEK—TUESDAY.

FORMATION OF SOILS.

I HAVE already observed, that the simple earths are produced by the decomposition of rocks, and it may be proper to show how this process takes place. This I shall do in the words of Sir Humphrey Davy, who has expressed himself with much philosophical precision, and, notwithstanding the scientific terms he employs, with sufficient plainness to make his general meaning understood by an unscientific reader.

"The manner in which rocks are converted into soils, may be easily conceived, by referring to the instance of soft granite. This substance consists of three ingredients, quartz, feldspar, and mica. The quartz is almost pure siliceous earth, in a crystalline form. The feldspar and mica are very compounded substances, but contain silica, alumina, and oxide of iron. In the feldspar there is usually lime and potassa; in the mica, lime and magnesia. When a granitic rock of this kind has been long exposed to the influence of air and water, the lime and the potassa contained in its constituent parts, are acted upon by water or carbonic acid, and the oxide of iron, which is almost always in its least oxidized state, tends to combine with more oxygen. The consequence is, that the feldspar decomposes, and likewise the mica, but the first the most rapidly. The feldspar, which is, as it were, the cement of the stone, forms a fine clay; the mica, partially decomposed, mixes with it as sand; and the undecomposed quartz appears as gravel, or sand of different degrees of fineness. As soon as the smallest layer

of earth is formed on the surface of a rock, the seeds of lichens, mosses, and other imperfect vegetables, which are constantly floating in the atmosphere, and which have made it their restingplace, begin to vegetate. Their death, decomposition, and decay, afford a certain quantity of organizable matter, which mixes with the earthy materials of the rock; in this improved soil, more perfect plants are capable of subsisting. These, in their turn, absorb nourishment from water and the atmosphere, and, after perishing, afford new materials to those already provided. The decomposition of the rock still continues; and at length, by slow and gradual processes, a soil is formed, in which even forest trees can fix their roots, and which is fitted to reward the labors of the cultivator."*

To this account, I may add that of Dr. Sigmond, who thus clearly and elegantly describes the process by which a vegetable soil is gradually formed: First, upon the burning sand, or naked rock, the simplest structure of vegetable life, the lichen, almost invisible to the eye, fixes itself, blown possibly by the breeze. Its generation is scarcely understood,-it boasts no flowers which require time for their developement, or food for their secretion. They struggle through their ephemeral existence, either upon the confines of eternal snow, or upon the scorching regions of the torrid zone; they fulfil the general law of Nature; they die; but in their death they are the harbingers of life: they decompose; the particles of which they are formed, unite with the oxygen of the air; an acid is the result, which eats its way into the crevices of the rocks, or insinuates itself amid the sand, when its other particles form new combinations, and, burying themselves, become a first layer of vegetable mould; cracks and crevices thus are formed, in which moisture is deposited; these become enlarged, either by the expansion produced by heat, or by frost; the granite mass is burst asunder, or slow disintegration occurs. In the thin stratum of mould, a tribe, a little higher in the scale of vegetable life, is developed, probably some ele

* Elements of Agricultural Chemistry, p. 188.