LECTURE EIGHTH.

RELATIONS OF CHEMISTRY TO THE DOCTRINE OF MANURES.

GENTLEMEN:-The subject of the lecture this evening is, The Relations of Chemistry to the Doctrine of Manures, or in other words, the improvement of the soil by chemical means. You will recollect, after I discussed the composition of the soil, and showed you, that when fertile it contained always certain substances in various proportions, that I then drew your attention to the modes in which the soil might be improved; that I stated there were two methods of doing this, one mechanical, the other chemical, and that I discussed the mechanical method, which consisted chiefly in deeper ploughing, subsoiling and draining. The improvement of the soil by chemical means, is more important, though no one result is more important than another to the farmer, except as one is more profitable than the other. It is quite certain, that no chemical improvement whatever, can result in higher profit than one or other of the mechanical modes I have stated: ploughing deep, subsoiling and thorough drainage. Still, supposing the soil to be already improved in this way, then come in the new, or chemical methods, by which it can be still farther improved, and it is one of those indirect advantages resulting from thorough drainage, that after it has been introduced and the soil made dry, you can then employ the means which chemistry puts within your reach. But if not thus improved, chemical means often prove ineffectual.

As to the chemical mode, it is what we understand by manuring, and by manure, we understand anything that feeds the plant, and corresponds with the food given to animals. Now, to understand fully every substance employed as a manure to feed the plant or prepare food for it, we must know what a manure should contain, and why it should con. tain these things. But as preliminary to the answer to this question, we must inquire what kinds of food the plant needs, if the object or purpose of manuring be to supply food to the plant. Thus, if we know what food the plant requires, then we know what manure is to be put on. I explained the evening before, that the plant consists in great part, of two forms of matter, one of which, and by far the greater part, was the organic form of matter, and that the inorganic or mineral part

was the smaller portion. In explaining the organic part, the starch, gluten and fat, and the woody fibre, I told you that there were certain elements of these substances, which the plant derived from the air, in large proportion, and certain other elements from the soil only, and that of those elements derived from the air, nitrogen was one only. I told you that the mineral part or ash, is wholly from the soil. Now, all manuring is applied to the soil; therefore, whatever the plant draws from the soil, these substances or manures should contain; and the first thing we must study in regard to manures is, what they should generally contain, if they are to make all plants grow under all circumstances, for we may have a very barren soil, and which itself would produce no crop whatever, as you recollect I showed you on a previous occasion. Now, on such a soil, if you apply a manure which shall make any crop grow, then you know, it should be such as should bring it up to the kind of land called fertile. These general manures should combine all that a plant requires to build it up, the nitrogen, which I call gluten and these mineral substances, lime, potash, magnesia, phosphoric acid, and chlorine. All these substances, this manure must add to the soil, if it is to make plants grow under any circumstances.

In considering the different kinds of manure, our attention is drawn to three different classes of substances, which naturally present themselves in divisions: 1st, vegetable manure; 2d, animal; 3d, mineral. The one derived from vegetable substances, another from parts of animals, and the mineral, from the substances occurring in nature, or which can be extracted from rocks; and there is a fourth class, more important, perhaps, than all; those which result from the application of science to this subject, viz: the artificial manures, which are compounded with reference to what we know to be the wants of the plant. Let me draw your attention to these manures, with this preliminary observation, however, that though we arrive, from these considerations, at certain conclusions, as to what the plant requires always, that is certain organic and mineral matter; yet we cannot be sure that certain vegetable or animal or mineral substances contain them all; but we can be certain that those manures, which we make up, shall contain them all. As to the several kinds of manures; and 1st, the vegetable They are applied 1st, in the green or in the dry state. Green manuring is the turning into the soil vegetable matter which is growing; as when a crop of clover is ploughed in, or when the sward is ploughed up, and the grass buried, or when green crops, grown for the purpose, are left to decay; for crops are often sown for the mere purpose of ploughing them in. Liguminous crops are very good; clover is

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very good; lupines are cultivated largely in Europe and sold for maThe crop is ploughed in before it ripens. So in northern America, buckwheat is sowed for a similar purpose, and many other plants are sown, to be turned in for manure, when in a certain state. This is one of those methods, within the reach of every man, and which in this country may be used to advantage when the land is exhausted. In many parts of America, where I have been-I do not refer to this State-these exhausted soils occur, and where the difficulty of obtaining these fertilizing substances, except from a distance, is very great. Hence, any method which the farmer has within his reach, and by which he can most easily restore strength to his land, must be the best; and this method of ploughing in green manure is very effectual.

How does this act? I have spoken of the lupine, which is analygous to peas and beans. You recollect that last night I showed you the composition of different crops, and among the rest, that of the bean and the pea. You will recollect that they contained 24 or 25 per cent. of gluten, and that even in the straw of these, there is as much gluten as in wheat. The nutritive quality of the straw, of the bean and the pea, would be as great as that of wheat; consequently, you see in this, one of those deductions, which the analogies of plants enables us to draw. The lupine has this quality; it is rich in gluten, containing, among other things, nitrogen, which it has taken from the soil only, and therefore if you bury it in the soil, you enrich it with this gluten, which is so important an element to the growth of plants.

Further by ploughing in green crops, you introduce another element. You know that all plants contain mineral matter; the bean and pea contain considerable. The roots of a plant go down as far as possible, if the habit of the plant is that way. Beans and peas go down to a great depth, in search of food, and among this food, are the mineral matters of which I have spoken-lime, potash, soda, &c. The roots send this up into the stem of the plant; they bring it from below, above the surface, or into the stem of the plant. But in this way, they do not get into the material of the surface; but if you plough in the plant, you supply the surface, not only with nitrogen, but with mineral matter. Thus you employ the roots of the plant to bring up from below what you want, upon the surface. This is the philosophy of green manuring. It does not put anything new into the soil, but it brings up from below, and puts upon the surface that which renders the surface fertile.

But besides green manuring, marine plants are often used-such as sea weed. This is another form of green vegetable matter. It is used on the sea coast; and in Scotland, it is considered so valuable a manure

that the right of way to the sea-side, adds a large additional rental an acre to lands. Now sea-weeds contain a large quantity of organic and of mineral matter. There is a table, (pointing to a diagram,) showing the composition of sea-weeds-that they contain about ten per cent of mineral matter. They are exceedingly rich in it, as you might suppose from their growing in salt water. They contain some 38 per cent of salt; phosphate of lime is also present in sea-weed; phosphoric acid also. In short, in this form of vegetable matter, we have a certain quantity of what crops require; so that if you lay it on land, or plough it in, it is found to be productive of great benefit.

Besides these forms of green vegetable matter, there are many others, which I pass over; but it is often applied in a dry state. You know there is a form of vegetable matter, such as the husks of grain, known as bran, which is given to cattle, pigs and other stock, for food, as well as to fatten them. This bran contains much mineral and organic matter, of a very rich and fertilizing kind, and hence it is often applied, instead of feeding it to stock, as a manure, and is found to be very beneficial to land, causing it to produce very good crops. But there is another form of dry vegetable matter, used with us, as a manure; it is one of those substances I spoke of last night, viz: the cake that is left when oily seeds are crushed. This cake contains all the remainder of the constituent parts of the seeds, the composition of which, I showed you last night. The linseed cake is too valuable to be used as a manure; but the rape cake, which cannot be much eaten by cattle, is extensively employed as a manure and with great effect. Perhaps I may use this as an illustration of the mode in which our farmers profit by high manuring, and though it may seem to partake of the nature of speculation, it is an adventure which is certain in its results. Suppose here are two farmers, occupying two farms, cultivating each 40 acres of wheat. The one ploughs and manures his land in the ordinary way, and the wheat comes up like his neighbor's; the other, after ploughing and sowing, leaves the rest to providence. He does not trouble himself, except perhaps to take out the weeds, leaving his crops to the influence of the seasons. But the other man does more; as soon as the grain is up, or when it begins to shoot, he applies a quantity of rape cake. This is over and above what the other man does to his land; and for his crops, he gets perhaps 50 shillings worth of wheat for 40 shillings worth of rape dust-besides a great quantity of straw. This is the way in which our farmers, by high farming, make money. It is laying out money in fact, to get it back with interest in another form; and you will readily see what I have often seen, wherever I go, that the man who farms highest, makes the most money.

So the You know

I pass now to the subject of animal manure. This is of various kinds, consisting of parts of animals; blood and flesh are often employed as manure. In some parts of the world it is dried, and sold in a dried state; sometimes it is dried by artificial heat, and applied in a dry powder, and is an exceedingly fertilizing substance. So with the flesh of animals; dead animals are often buried, as a manure. refuse of animals is employed, more or less, as a manure. the composition of the muscle of animals: it contains 77 per cent. of water-a solid beef steak contains that amount of water. It will surprise you, perhaps, to know that the blood in your veins, as well as in animals, contains the same quantity of water that the muscle does, and differs from the flesh in no degree. Dry flesh has exactly the same composition as the blood. Burn them both, and the mineral matter left is nearly the same. The ash of the blood and of the flesh contains phosphoric acid and phosphate of lime in large quantities. Both, therefore, are extremely fertilizing, as they contain the mineral matter that the plant requires; and the organic matter that burns away is identical with the gluten of the vegetable, and supplies the nitrogen of which the gluten is built up.

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Fish, in many parts of the world, are employed as a manure. the sea coast in this State, and other north-eastern States, fish are employed extensively as a manure. Muscles, in England, are often buried in the soil as a manure. Sprats, also, are obtained in great quantities, and employed in the same manner. Among other interesting things I have learned in the State of Connecticut, is the fact that fish are obtained there in large quantities, and are now manufactured into a fish cake. The oil is expressed, and the cake is dried, and is found to be exceedingly fertilizing, consisting of animal matter and bones, with a little oil remaining in it. I understand that it is intended to export it to Liverpool. I believe it will find a ready market there. Shell fish are another form of animal matter, applied as a manure. In some parts of northern America, the muscle is found in great abundance in the mud banks on the coast. In England, we use them as I have said; so on the coast of New-Brunswick and on the borders of Maine. These muscles are obtained and ploughed in. So with sea mud; that is a fertilizing substance. I have explained to you, in a previous lecture, how it is that this alluvial mud is so rich, and you will recollect how large a quantity of animal matter it contains.

But among the forms of animal matter most extensively employed in England, where Agriculture forms a species of trade or profession, which is pursued with great intelligence and skill, are bones, and they are ap