under the influence of oxygen and moisture;—readily giving up its elements, in the form of carbonic acid, carbonate of ammonia, phosphate of lime,-it is easy to conceive how it may promote vegetable growth, and especially the growth of those plants into the composition of which much azote and phosphate of lime enter, as in the instance of all the cornbearing grasses, and all the leguminous plants, and, in brief, all those which are highly nourishing as the food of animals. When I speak of animal matter, I speak of it almost without exception, every part of an animal-(excepting, indeed, fat, a substance which contains no azote or phosphate of lime)— being adapted by its composition to have a fertilizing effect, whether bone or hair, skin or muscle, whether blood or urine. This general fitness of animal matter for the purposes of manure is most deserving of being kept in mind, associated with the fact, that the animal matter does not act, except when undergoing decomposition; that is, it is not the blood that fertilizes applied to the soil, but the elements of the blood, and so of the urine and other excreta. I beg to call your attention to this, because it appears to me that economy is not observed in the West Indies in the use of animal manures. Large quantities of guano are imported at a great cost, and applied to your cane-fields, whilst the bones of all the cattle that are killed for the market, or die of disease, are neglected. I speak of guano and bones thus together, because guano contains a large proportion of the same ingredients as bone, viz., phosphate of lime, and so far they are adapted to act the same part. Besides phosphate of lime, guano contains ammoniacal salts. It is a matter, as you are no doubt aware, derived from the excreta of sea-fowl-their urine and dung, partially decomposed. Its nature should be remembered: it should be remembered that the excreta of other animals are hardly less valuable, and, without exception, and as before observed, these are the matters rejected by animals, and noxious to them, which seem by nature specially intended to be the food of plants. Though it little atbracts common attention, there is not an animal in its wild state that does not promote vegetable life; the urinary secretion of the smallest insect differs but little from that of

the sea fowl, the source of guano; and, in consequence, even when insects are destructive they may fertilize, so that sometimes it may be a problem whether the good effected by them in one way may not preponderate over the evil they occasion in the other. But it is not my wish to appear paradoxical; I mention these circumstances because I believe them to be deserving of attention, and fit to illustrate the nature of animal manures.

3dly, Of the fertilizing means derived from vegetable matter. That vegetable matter should be fit to be the food of plants, is most easy to conceive a priori; and that it is fit, is proved by the most extensive experience, and this, generally, and without exception, in different degrees, as in the instance of animal matter; and, also, as in the instance of animal matter when undergoing decomposition, that is, when under the influence of moisture and atmospheric air, the vegetable matter is becoming resolved into the compounds from whence it originated. It is a happy circumstance for agriculture, that vegetable matter in a dry state undergoes little or no change on the surface of the soil; it also is a happy circumstance, that it undergoes little or no change under the soil, even when moist, if atmospheric air be excluded. Moisture and atmospheric air are essential to the growth of plants; and, being essential also to the decomposition of vegetable matter, the latter takes place when it can be useful to the former. One of the peculiarities of cane cultivation in Barbadoes, and, I apprehend, a very judicious one, is the strewing of the leaves of the last crop on the surface of the cane-field to protect the young plants from the sun's rays and from parching winds. Conjoined with this effect, is another which takes place, though I believe not contemplated, viz., that of manuring the young canes. long as drought prevails, the old leaves are protectors, themselves unchanged; so soon as the rains set in, even if there be only a single shower, their decomposition commences, and their fertilizing influence is exerted.

So

An idea commonly prevails, that soils by long culture are worn out and exhausted. Under one system of cultivation VOL. XLIII. NO. LXXXVI.-OCTOBER 1847.

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this may be, as when the crops, the produce of the soil, ar in no part returned to it; but, it cannot be in ordinary course if the reverse practice be observed; the tendency of vegeta tion being to enrich the soil: in brief, the great fertility o what are called virgin soils, appears to be owing, not to state that the word implies, but to the plants which hav grown on such a soil, having undergone decay there, and by their decay manured and enriched the soil. Take the ex ample of a native forest :-the trees composing it spread their roots in all directions and to a considerable depth, from whence they collect the inorganic materials requisite; these are conveyed into the leaves and into the wood of the trunk and branches, in which also, carbon, derived from the atmosphere, is stored; the leaves fall and decay, and, in time, the trees, and decompose, and in decomposing give carbonaceous matter to the soil, and restore the inorganic materials extracted, and as it were, collected and concentrated. Such is the natural tendency of vegetation; and such also is the effect of judicious management, when green crops are ploughed-in as manure, or when the greater part of the ripe crop is returned to the soil, whether directly, as in the instance of the application mentioned of the leaves of the cane to the surface of the soil; or, indirectly in the state of stable-dung, or penmanure, the vegetable matter having been first used as forage. This view is simple and clear, resting on the principle that vegetable growth and the enrichment of the soil are concomitant; and, I believe, that generally it is a principle of practical application. There are, however, facts deserving of attention, and of careful study, which prove that the growing of plants of the same kind for a series of years, the plants decaying where they grew, has an injurious effect on the soil, as regards its power of supporting these plants, indicated by their disappearing, followed by other species which grow luxuriantly, proving unexhausted fertility, that is, that the soil has been so modified by one species as to be rendered unfavourable to it, and yet favourable to another species. Now, what is witnessed in a striking manner as the result of a long series of years in the soils under forest growth, may take place, though not in a marked manner, from year

to year in artificial culture; one plant, though not carried off the soil, may be injurious in preparation for a crop of another plant. I make this remark, keeping in mind a fact which was mentioned to me by a gentleman of Barbadoes, one of its ablest practical agriculturists; it was, that on some estates in this island, the growing of guinea corn, and the ploughing or turning it into the soil in its green state, had a decidedly injurious effect. This partial effect, and the effect before alluded to, are problems which are yet unsolved, doubtlessly admitting of solution, but of solution which can only be attained by scientific inquiry. In the instance first mentioned, the soil beyond a certain depth may be exhausted of the inorganic matter required by the plant, and which may be accumulated at the surface in a state unfavourable to the exhausting species, and yet favourable to another species. In the last mentioned instance, the guinea corn may so unite the inorganic elements which it extracts and returns to the soil, make such compounds of them, as to be unfavourable either to their solution and entering the sap, or, if soluble, to their affording supporting nourishment to the cane. These are mere conjectures; but whether true or false, can be determined only by exact research.

Lastly, Of the fertilizing means derived from mineral or inorganic matter.. The most fertile soils appears to be those which are most compounded, which contain the largest number of the inorganic elements of plants, and in a state of minute division, favouring their solution to enter into the composition of the nutritive sap. Lime, magnesia, silica, potash, phosphate of lime, may be mentioned as the most important of these ; and these may exist in the soil in different states, either as free, uncombined, or in combination, constituting mineral species. If the former, they are more readily yielded up to the growing plants, and the soil without care is in danger of being sooner exhausted; if the latter, they are yielded up more slowly as the minerals decompose, and, in consequence, exhaustion, even with bad management, is difficult. Such fertilizing means as these in the soil, depending on its supplying the inorganic elements of

this may be,-as when the crops, the produce of the sc in no part returned to it; but, it cannot be in ordinary c if the reverse practice be observed; the tendency of v tion being to enrich the soil: in brief, the great fert what are called virgin soils, appears to be owing, n state that the word implies, but to the plants whic grown on such a soil, having undergone decay there, their decay manured and enriched the soil. Take ample of a native forest :—the trees composing it their roots in all directions and to a considerable depe whence they collect the inorganic materials requisite are conveyed into the leaves and into the wood of the and branches, in which also, carbon, derived from the sphere, is stored; the leaves fall and decay, and, in t trees, and decompose, and in decomposing give carbo matter to the soil, and restore the inorganic mater tracted, and as it were, collected and concentrated. the natural tendency of vegetation; and such also is