the surface in a s es and yet favours ned instance, the ments which it ex mpounds of the ition and entering porting nourisher, ut whether tre ac research. erilizing means derived tra The most fertile soils del which contain the ements of plants, an 12 chicombined, or in comb the former, ther ig plants, and fie sa hausted... Not ires, is is east nct; ach, ient, whe 1 for, ; and it not urish aided lp, no d, ad urish taking e, that fection, t be debject to 1 accomchemical ses, such These are being con the straw exhausting to allow the uring which, n of mineral it from the atid by rains and cing roots of nathe loss is made ed away :-or, in a manure (aided by inats abstracted and lost plants, are obvious. There is another source of fertility in the soil of a more obscure kind. There are some soils, for example, capable of yielding nitre, and that for successive years. Nitre, you know, is a compound of nitric acid and potash. When formed in a soil, there is reason to infer that invariably the alkali is furnished by the soil, derived from a compound mineral, and that the elements of the acid, azote and oxygen, are furnished by the atmosphere, and that in consequence of certain ingredients in the soil, favouring the union of these elements, especially lime, the acid is formed and the salt is produced. So there are other conditions of soil in which clay, and perhaps oxide of iron, act a part, promoting the production from its elements, viz. azote and hydrogen, of ammonia, or the volatile alkali. And, as the substances first mentioned, lime, magnesia, potash, silica, are fertilizers as inorganic elements; these latter, nitre and the volatile alkali, are probably useful in administering to the formation of the organic parts. In taking a view of the capabilities of a soil, the attention should be given to the under portion, to the subsoil as well as the surface soil. If the latter be neglected and never turned up and brought into use, great may be the loss to the agriculturist. Water holding carbonic acid in solution, I have endeavoured to shew, is the principal agent or menstruum by which the sap is formed and plants are fed. This is the result when it is absorbed by the roots, and is transmitted by their ascending to be distributed to the various parts where required; but when, instead of being thus absorbed, it passes from the soil to the subsoil, it impoverishes the former and enriches the latter, removing out of it more or less of the soluble constituents, so that you may have at the same time an exhausted surface soil and a rich subsoil, requiring only a change of place, it may be, a mixing of the two, to become highly productive. Gentlemen,-I must now bring this discourse to a conclusion. As I began it with drawing your attention to the analogy between plants and animals, I do not know how I can better finish it than by reverting to that analogy. All I have hitherto said, has been on the subject of manures generally, as involving common principles, universally applicable. Not a less important part of the subject, is that of special manures, or of the choice of manures for particular crops, and this is by far the most difficult part, and the one hitherto least studied. In animals, their coarser organization is distinct; if we examine the teeth of any particular animal, its stomach, its intestines, the main organs concerned in its nourishment, we have no difficulty in deciding from their structure, whether the individual is carnivorous or herbivorous, or fitted for, and requiring a mixed diet of animal and vegetable food; and this, be it one of the mammalia, birds, or insects. But not so as regards plants; the organs concerned in their nourishment are so minute as to escape detection by the eye unaided by the microscope; and even when examined by this help, no differences characteristic have hitherto been detected, admitting of being associated with the quality of the nourishment best fitted for the individual plants. This, then, taking it for granted, and it seems to be proved by experience, that different kinds of plants do not for their coming to perfection, require one kind, but different kinds of manure, must be determined by other means. How is this important object to be accomplished? I do not know how it can be well accomplished, except by enlightened experience and by chemical research. In the instances of the corn-bearing grasses, such experience, such inquiry have been highly useful. These are crops which are exhausting to the soil,-the grain being consumed at a distance, and the more exhausting when the straw also is removed from the farm. To correct the exhausting effect, one of two measures is adopted; either to allow the land to remain fallow for a certain period, during which, owing to the decomposition and disintegration of mineral particles in the soil, and the addition made to it from the atmosphere by the agency of the elements, and by rains and winds, and from the subsoil, by the penetrating roots of native grasses and other indigenous plants, the loss is made good of those inorganic materials carried away :-or, in a more summary manner, by restoring in manure (aided by intervening green crops), the ingredients abstracted and lost in the grain and straw; in the former, chiefly phosphate of lime and azote; in the latter, chiefly silica. The summary or shorter way, last mentioned, is the improved method, the result of scientific research; the tedious way, first noticed, is the result of mere experience unaided by such research, and is in many respects imperfect. The same remarks, I believe, are applicable to every kind of crop. Take the most important with which the interests of the West Indies are connected, the sugar cane. For its most successful cultivation, that is, its most profitable, as regards its produce and returns, supposing the fallow system to be put aside as least judicious, it needs to be determined what kind of manure is best fitted to bring the cane to its perfection of growth as a sugar bearing plant, and with most economy, keeping in view the balance sheet of an estate. If the problem is entered upon by the agricultural chemist, as I apprehend it should be, he will have to consider what are the elements constituting sugar; they are oxygen, hydrogen, and carbon, elements derived from the atmosphere, either directly or indirectly: he will have to consider what are the elements of the saccharine juice, as extracted by pressure from the plant; these, besides sugar, are, I believe, chiefly starch and albuminous matter, or a matter containing azote, and capable of exciting the vinous fermentation, and one or more vegetable acids: he Iwill have to consider what are the elements of the cellular structure of the plant in which the saccharine juice is contained, and the composition of the other parts of the cane; these appear to be very much the same as the constituent elements of the stalk and leaves of the other grasses, viz.phosphate of lime, silica, lime, magnesia, and potash, with the common elements, carbon, oxygen, and hydrogen. Having given consideration to all these matters, he may offer suggestions for trial. As the cane contains little azotized matter, and pure sugar none, he may suggest that the manure most likely to be successful is one composed chiefly of vegetable matter, or one in which the proportion of animal matter is small. As the sugar and other exports, viz. rum and molasses, contain very little of any matter of a mineral kind derived from the soil, he will conclude, that with good management, a cane-crop is not exhausting; and that if the leaves and stalks are returned to the soil, the land instead of being impoverished, may be actually enriched, in as much as there is given to the soil a vast accession of vegetable matter, the elements of which have been obtained from the atmosphere, and which, in decomposing, render up these elements to support the growing crop, being, as it were, to the young plant what the milk of the mother is to the young animal. I should add, that the inquiry of the agricultural chemist will by no means be complete, unless his attention also be directed to the soil, and that not only once, but at intervals. If, on his first examination of it, he find a marked deficiency in it of phosphate of lime, and of other inorganic substances which seem to be essential to the composition of the sugar cane in its healthy state, he will suggest the use of guano as a manure, or of bone-dust, or of marl containing phosphate of lime, according to circumstances. If, after an interval of a few years, the land having yielded good crops, he examine the soil again, and now finds in it no marked deficiency of phosphate or carbonate of lime, or other supposed requisite inorganic ingredient, he will, I conceive, be warranted in suggesting the sparing the expensive manures, the guano and the bone-dust, and using only manure chiefly vevetable, made on the estate. Such, I fancy, is the line of inquiry, as regards particular manures, that is likely to be most useful, and the more useful, I cannot but think it will be, the more minutely, and carefully, and judiciously it is carried out, testing theoretical suggestions founded on chemical analysis, by the results of practical experince, that is, by well conducted trials, and extending them from point to point, till satisfactory knowledge is arrived at, so that being acquainted with the quality of the soil, the quality and quantity of manure applied, the mode of tillage employed, the planter may be able to calculate, communibus annis, what will be the quantity and quality of sugar, what the quantity and quality of the molasses, and what the quantity of rum, that should be made on his estate. The subject of manures is far too large a one for a single |