practical Agriculture, and the profit of it. And though the farmer may not see the bearing of these researches immediately, yet results are always arrived at, which are capable of a direct and practical application to the farmer's art, and when the range of the sciences shall be still farther extended, we can then extract from them all a system of principles, by which a practical and sound system of Agriculture can be established.

LECTURE FIFTH.

(This Lecture was delivered at the annual meeting of the Society.)

THE RELATIONS OF CHEMISTRY TO THE SOIL AND ITS PRACTICAL

IMPROVEMENT.

The Hon. John A. King, President of the State Agricultural Society, called to order, and introduced to the Society Prof. Johnston, who addressed the society as follows:

MR. CHAIRMAN AND GENTLEMEN: As there are present this evening a number of persons who were not in attendance at my former lectures, perhaps you will excuse me for mentioning, in order that the object of this course of lectures may be understood, that the purpose in view has been to present a general idea of the relations which science bears to practical Agriculture-not, of course entering into those details which the wide field presents-but dwelling only on those general aspects which hold a striking relation to this most important of all arts. Such of you as were at Syracuse, may recollect that I then mentioned that I might select illustrations, of the applications of science to Agriculture, and present them to you on the occasion of your annual meeting. As that address is now in your hands, you may readily ascertain how far this purpose has been carried out. The first of these lectures was on the relations of physical Geography to Agriculture; the second on the relations of Geology to Agriculture; the third on the relations of Botany and Zoology to Agriculture, and the last, on the relations of Meteorology to Agriculture. I may, perhaps, add to what I have said, that each of these lectures, being on a separate subject, is entire and complete in itself, and therefore contains in itself all the elements necessary to a comprehension of the general bearings of each subject to practical Agriculture. Thus this lecture, which has reference to the practical improvement of soils, will not draw on previous lectures.

Gentlemen, in drawing your attention to the relations which Geology bears to Agriculture, I pointed to this map of your own State and showed you the different kinds of rocks represented by different colors, of which the surface is composed, and I explained the process by which the va

rious kinds of soil were formed-that is, by the crumbling down of rocks, of different formations, and that these materials constituted the chief ingredient in all soils. By this crumbling down of the rock, a loose material is produced, which formed, I would say, a substratum, in which the seeds of plants might take root and vegetate. These plants coming to maturity and dying, and others succeeding them to mature and die, with the insects and animals which feed upon them, and the remains of all being mixed up with the rocks in a disintegrated state-these form what we call soil, on which the labor of man is expended and crops are grown. Hence the origin of soils is, first, the solid rock; and second, the remains of vegetables and animals, which, while they enrich the soil, also give to soils that variety of character which exists.

In considering the quality of soils, there is one point to which it is necessary to draw your attention that is, to the chemical relations of soils. I formerly drew your attention, and now do so again, to the fact that if you take the same kind of matter, exactly, you may convert it, without changing its chemical composition, from one mechanical condition to another. Thus, this piece of plastic clay, which would be difficult to till, may be converted into the hard, solid brick, which, if pounded out by artificial means, or crumbled down by atmospheric action, becomes a soil very easily cultivated. This mechanical character of the soil very much controls the kind of plants that will naturally grow on it. On very light lands, rye, of all grains, grows best; and of all food for cattle, spurry grows best on light, sandy soil. In Europe, it is considered an exceedingly milk-producing food for the cow. On loamy and gravelly soils, you know, barley is a kind of grain that grows best; turnips and Indian corn also do well on such soils. In fact, barley could not grow on a stiff clay, such as I have exhibited here; but it would grow well on the brick that is made of it, pounded up, and forming a loose and open soil. But on heavy, clay lands, wheat, clover, and grass grow most luxuriantly; and I showed you, the other night, that a stiff clay soil, though it would not pay for cultivation, will pay well if devoted to pasturage.

These physical characters of soils are of great consequence; and whilst I shall show you that the chemical composition has much to do with their fertility, and that after a soil is exhausted, and the art of man is brought to restore it, success depends greatly on a knowledge of this chemical composition, yet, I shall show you that whilst a knowledge of chemistry is important, the physical or mechanical condition of the soil is not to be slighted, and indeed is the first thing to be re.

garded, and is, after all, considered more essential than that which we cannot see, and for the most part know nothing of.

I pass this over, and turn now to the chemical composition of soils. What does this piece of plastic clay contain, and what this hard brick? Both contain the same matter. In order to obtain that knowledge which shall be useful to us, as practical men, in tilling the soil, we must begin with some soil of known value and fertility, and which is known to produce good crops in ordinary seasons, and with ordinary treatment. When such a soil is taken-and there are many such here, particularly in the virgin soils of the West-we find it to possess a great variety of combinations. Before going further, I will repeat what I have said before, that all rocks consist of one or more of three kinds of matter-limestone, sandstone, and clay, or we have mixtures of them. This general view enables us to form an opinion of the physical character of soils at once. Sandstone gives a light, open soil; limestone, also; and clay, generally a stiff soil. Sometimes the clay is hardened, and the soil assumes a different character, like brick. But when you come to put these soils in the hands of the chemist-I mean these virgin, pure soils, which grow large crops, with little aid from labor-the chemist is not satisfied with the knowledge of the fact that they contain lime, sand, or clay, for he knows that clay itself is a complex substance, before he submits it to chemical analysis. He finds, as might be expected, that he extracts from soils these various substances, exhibited in this table:

Composition of soils of different fertility.

But first of all, let me draw your attention to a fact. If I take a match and ignite it, and allow it to burn away, you will find that a small portion remains behind after the greater part is burnt away. The part that remains is the wood ash. This is the result if you burn any vegetable substance whatever, and as in soils there is both vegetable and animal matter, if you burn it, a portion of it is burned away; but that portion always leaves a quantity of ash. But this matter will be more fully explained at our next meeting. The part that burns away is called the organic part, or organic matter; and the part that is not burnt, consists first of silica, which means flint, and then alumina, that is, the substance which gives tenacity to the clay. If I dissolve clay in water, and into that pour hartshorn, it immediately becomes milky, and a white substance is precipitated, called alumina. It exists largely in clay, and is what gives its tenacity.

The soil also is found to contain lime, magnesia, oxide of iron, potash, soda, chlorine, which is a kind of gas, of a greenish color, having a peculiarly strong odor and very heavy, and in this respect distinguishable from common air; a taper will burn in it, but will give but little light; it burns red, smokes, and soon goes out; it is so heavy that it can be poured from one vessel to another. This gas possesses many properties, but it is quite enough to know at present, how to distinguish it from other gasses or air. It may strike you as curious, that this gas exists in the soil, and chiefly in the form of common salt; indeed, every ten pounds of salt, contains about six pounds of this gas. Sulphuric acid and phosphoric acid, also form parts of the soil. Let me draw your attention to the fact that if you ignite a lucifer match, it emits a peculiar odor; that is the odor of phosphorus. When the match is first lighted, you perceive a white smoke; that is phosphoric acid. Carbonic acid also exists in the soil, but I will not dwell upon that now, as I shall speak of it in my next lecture.

The soil, therefore, when chemically analysed, is found to contain many other substances, than sand, lime and clay, and enables us to enter into the minutest kind of reasoning, as to the functions of the soil, in relation to the plant, and how the soil is to be improved. It is of great consequence to understand this composition of soils, and any one who wishes to know how to manage the soil intelligently, should attend to many things besides the substances it contains. You will see by reference to this table, that 1000 parts of a given soil contain 648 parts of silica, 57 parts of alumina, and 59 of lime-that is to say, that though all these things are present in a fertile soil, they are not so, in the same proportions, but that they vary in a certain ratio, in the most fertile soils.