ment, for the mutual action of the elements of silicates, derived from their admitted electrical states, yet the amount of this action is never measurable in one season. Being silicates, they have no tendency to act on each other. We can only excite this action by introducing new elements, salts, which in this sense only, can be said to be excitants or stimulants. The silicates are the flour, the salts the yeast. The galvanic agency is excited by the salts, but above all, over all, and controlling all, this action of soils is the living plant."-Dr. Samuel L. Dana.

Manure.

Manures are either substantive, that is, the food of plants in a soluble state, or adjective, possessing the power of rendering soluble the geine of the soil. All animal substances, the droppings and urine of cattle included, are, in part substantive, and in part adjective manures. Undergoing decomposition, they give out ammonia, an alkali in the form of gas, but capable of uniting with water, and which, like potash and soda, is a solvent of geine. It is a compound of one volume of azote, and three volumes of hydrogen. During the process, which converts fresh into well rotted manure, ammonia escapes and is lost. If the rotting manure be covered by soil, or what is much better, peat muck, the ammonia unites with the geine, and makes a valuable compost. Economy requires that all barn manures, in their fresh state, should be mixed with such muck to form compost.

Geine, or substantive manure, is the product of putrefaction. The art of causing vegetable matter to putrefy without running into the vinous or acetic fermentation, either in compost heaps, or when ploughed into the soil, is a desideratum in agriculture. Vegetable juices which contain sugar, starch, gum, and glutin, if exposed to air, moisture, and a temperature never below 50° F., nor above 86° F., ferment and are converted into gases, alcohol and yeast.

The first escape and are lost; the second poisons animals, and affords no nourishment to plants, and a small part of the yeast only remains to form geine.. Sugar and gum exposed to air, moisture, and a temperature of from 65° to 70° F., are susceptible of acid fermentation. The products are vinegar, carbonic acid gas, and some other acids. Here also is almost a total loss of portions of the plant, which by the putrefactive process, would have been converted into geine. Green plants, especially those which contain much starch, sugar, gum, &c., ploughed in, or placed in compost heaps, are liable to be lost in this manner. This explains what had for years been a puzzle to me. I once ploughed in as much green cornstalks as could well be covered with soil, in the month of September. And in subsequent years the soil was not in the least benefitted by it. It was, doubtless, converted into alcohol, vinegar, and gases;. poor food for vegetables. Dried plants give more geine than green-because they have parted with most of their sap, and from the moment when their living functions ceased, new combinations of their elements began, and decay, putrefaction commenced. Dry crops, and probably those killed by frost, will, I am inclined to think, be found most readily and with the least loss to putrefy and form geine. There must be also a great difference in different plants as to their tendency to putrefy or to run into vinous or acid fermentation. Here chemistry can prove the only sure guide to successful experiments. There is one other mode in which plants are decomposed, and that is by what is termed "destructive putrefaction." It is rather a slow combustion; it is seen where green plants are heaped together, and become heated, so that all except their inorganic constituents are literally burnt up and lost. Manure and compost heaps should never be permitted to thus run to destruction-but as soon as they begin to evolve steam, be spread open and cooled with water or otherwise.

Soot.

I have given above the constituents of ashes, but in decomposing wood and other vegetables by fire, other elements escape in the form of smoke, the more ponderous parts of which, are condensed on the sides of the flues that convey the smoke into the open atmosphere. Soot is a valuable article for compost manures. Dr. Dana gives the following

analysis of soot from Braconnot.

I shall on this subject abridge the remarks of Hitchcock and Dana. There is abundant evidence that our common clays are of great value when spread on land. When spread on dry sandy and gravelly land they render it a better reservoir of salts, geine, and water. But they exert other than a mechanical influence; in fact, their effect is similar to that of lime. An analysis of our common blue clay, gives Water and organic Protoxyde of iron, 9 Lime, magnesia, and sulphur, S

matter,

Silica,

Alumina,

.48

. 29

11.

3

100

It is, therefore, probable that most of the good effects of clay, as a manure, are owing to the large quantity of iron it contains. Iron in clay exists either in combination with oxygen or sulphur. Iron combines with two proportions of oxygen, and forms two oxids, the protoxide and the peroxide. The

protoxide consists of iron 3 parts, oxygen 1 part by weight. The peroxide contains a larger portion of oxygen. The protoxide is black, the peroxide is red. By exposure to the oxygen of the atmosphere, especially when heated, the protoxide imbibes the larger dose of oxygen, and becomes a peroxide. Sulphuret of iron is a compound of iron and sulphur. It is of a golden metallic color, and where it exists in massive rocks, often fills the imagination of the discoverer with dreams of wealth, never to be realized. By exposure to the oxygen of the atmosphere, the sulphur undergoes a slow combustion and is changed to sulphuric acid, which unites with the iron and forms sulphate of iron, green vitriol, or copperas. Understanding this, the following remarks of Dr. Dana will be understood.

“If we attempt to account for the action of clay, independent of its amending a sandy soil, we should bear in mind that our common clays contain more or less sulphuret of iron. The conversion of this into the persulphate of iron is the natural consequence of exposure; free sulphuric acid results, which acts on any lime in the soil, forming sulphate of limeplaster. So, by spreading clay we spread plaster of Paris. The iron in clay also plays its part thus: The protoxide of iron, unchanged, would not be beneficial in agriculture. It does not act on geine. By exposure, the protoxide becomes peroxide; and then begins an action similar to that of lime. If the free sulphuric acid, produced as supposed, finds not lime enough, it will decompose all earthy geates and thus a fresh portion of nutriment be set at liberty. Both the effects of clay, the production of plaster and the formation of the peroxide of iron, are speedily produced by burning the clay, as is often practised. Some facts have lately come under my eye, and have recalled others to mind, which I have followed up experimentally, all tending to show that if iron peroxidates itself in contact with vegetable fibre, the texture of the fibre is weakened and

geine is produced, and that in a few hours. It is during the passage from protoxide to peroxide that this saponifying' action takes place. Geine is produced and then combines with peroxide." And here Professor Hitchcock adds in a note, from Dr. Dana, "How wide is the influence of geine! It not only enters by itself into the food of vegetables, but becomes the very solvent which nature has prepared to act on the alkaline earths and oxids, dissolving them as they are liberated from decomposing granitic sand. By fermenting dung, vast volumes of ammonia are liberated. I do not think that it is the action of gases, as such, which we want, or which nature intends as food of plants to be derived from the soil. The air is always full of all which this fermenting manure can supply in a gaseous form. The true action of ammonia and carbonic acid resolve into their action on geine. The ammonia combines as alkali with that and thus it becomes very soluble. And the carbonic acid produces sursalts of the earthy geates of lime, and magnesia. It is these, liberated the moment the plant demands them, which cause all the geine of the manure to become alkaline soluble geates."

Marsh Mud.

This substance is so abundant and so accessible 'to a large portion of the farmers of the county of Essex, that it would seem desirable that they should know in what its value consists. It is generally, I believe, esteemed a good ingredient in composts. The marsh mud, however, of different localities, varies much in value. And the opinions of different practical farmers as to its worth differ accordingly.

A scientific analysis of specimens of marsh mud taken from different places, shews how little dependence can be placed on a name of soils, &c. in agriculture.