employed. The base of many of these is tar dissolved in naphtha; this is mixed with some substance such as oxide of copper, arsenic, or an alloy of copper and antimony, which is supposed to prevent the adherence of barnacles and other marine animals and plants. India rubber, dissolved in naphtha, has been used for the same purpose; lime soaps have also been proposed for this use. No substance has, however, been discovered that will resist the action of salt water more than a few months without requiring renewal; nothing that is known to chemists being absolutely insoluble in water. Lately there has been quite a flourish of trumpets over a certain compound invented in England by Count Szerelmy, and called zopissa. This is essentially a paint composed of boiled linseed oil, brown umber, lime water, sulphate of copper, Prussian blue, copperas, burnt clay, calcareous silex (whatever that may be), litharge, asphalt, read lead, gum animi, and turpentine. It was probably through mere modesty that the inventor stopped after adding these ingredients, and did not continue through the rest of the drug shop. The paint is no better and no worse than one containing an impure oxide of copper for pigment, and liuseed oil and asphaltum for the menstrum. It will no doubt protect the wood to which it is applied in sufficient quantities from external action, so long as it lasts.

The second method of preserving wood consists in removing as com pletely as possible the sap and protein matters contained in it, and then keeping the wood without further treatment, or impregnating it with some material that will tend to prevent decay.

The most common method of removing the sap, or rather, in this case, the water contained in the sap, is by simple air-drying. It is found by experience that the season of the year at which wood is cut has great influence on its keeping properties; wood cut after the fall of the leaf in the autumn, and before the ascent of the sap in the spring, being considered much more durable than that cut at other seasons. It is also of much importance that wood should be well ventilated, if exposed in damp situations; otherwise it soon commences to mould, and decay sets in. This may be frequently seen in the floor-beams of a cellar, and on the under side of boards laid next the ground. If, however, the wood is placed so as to be completely excluded from the air, as when buried in dock mud, it will last for a long-time, the buried portion of piles in such situations out-lasting the tops.

Wood may also be seasoned by being placed in water. Dialysis takes place, and the sap passes out, and the water in the wood is afterwards removed by drying. Much of the timber used in the navy-yards is seasoned in this manner. If boiling water be employed instead of cold,

this takes place much more rapidly, and a steam-bath hastens still more the process. But without subsequent treatment the benefit of steaming is doubtful, as the wood is rendered harsh and brittle.

It has been proposed also to remove the sap by mechanical pressure between a pair of large rollers, which are gradually brought nearer together. In England it is very common to employ a new vessel on her first voyage in the lime trade, as it is found that if thoroughly dried by this means she lasts much longer. Of late years it has been frequently the practice to pack all spaces between the timbers of a ship with salt, which preserves the wood in the same manner as it preserves meat and other substances susceptible of decay.

The sap may also be driven out of the pores of wood by the entrance of some substance which will prevent decay by forming insoluble compounds with the albumen of the wood. Creosote, crude carbolic acid, pyrolignate of iron, chloride of mercury, sulphate and chloride of zinc, sulphate of copper and sulphate of iron, have all been used for this purpose. One of the most simple methods of impregnating the wood is that proposed by Boucherie, who surrounds the butt of the recently felled tree with a tank containing the fluid, and allows it to be absorbed by natural action. This method will not, however, work on all kinds of timber, and is not very certain in its effects. Kyan, who used bichloride of mercury, simply soaked the wood in a solution containing about one per cent. of the salt. The process answers well for preserving the wood, the chief objection to it being the injurious effect of the mercury upon the health of the workmen. Burnett's method consists in impregnating the wood under pressure with a solution of chloride of zinc. This answers very well to protect the wood from dry rot, and from fungus in a damp situation; but in places where the water in contact with the wood is being continually renewed, it is not effectual, as the compounds formed by the chloride of zinc are not completely insoluble, and they may be removed by continued washing. Bethell's method consists in impreg nating the wood by strong pressure with dead oil. The dead oil owes its antiseptic properties to carbolic acid. Seeley's method is a modification of Bethell's. The wood is first treated with hot dead oil, until the moisture is completely expelled, in a strong iron cylinder; cold oil is then admitted, which completely fills the pores. The method is one of the most satisfactory that is in use, but for thorough treatment the cost is an objection. Another process consists in treating the wood with the vapors of dead oil, the air having previously been exhausted by an air-pump.

Wood may be treated by simple boiling in the dead oil. This is found to be very effectual with short pieces, such as are used for paving-blocks.

Dr. E. P. Morony, of this city, having observed that the direction of the flow of water in wooden paving blocks is always from below upwards, and that decay also takes place in the same direction, proposes to protect the wood by thoroughly disinfecting the sand upon which the blocks are laid, by means of carbolic acid or a mixture of dead oil and lime. He claims that the expense of treating the wood in this manner will be much less than by any other method, and that it will be as effectual. As fast as the water evaporates from the surface of the blocks, it is reabsorbed at the lower end, and this process is a continual one. This water, in passing through the carbolic acid and sand, must absorb more or less of the acid. This method may be found useful in laying beams for cellar floors and other timbers that come in contact with the ground.

Other methods have for their basis the production of insoluble salts in the pores of the wood, thus converting it into a stone-like mass; for instance, sulphate of iron followed by water-glass, or alum and chloride of barium or calcium. These processes, however, do not seem to be very successful.

If the wood is dipped into petroleum and then set fire to, the outside may be charred. This has been found very useful for posts and other articles that are to be buried in the ground, the coating of charcoal serv ing to protect the wood. It is said that the same object may be gained by filling the post-hole with charcoal. Wood buried in mines where iron pyrites abound is frequently preserved by the action of the water containing sulphate of iron. If the pyrites contain copper also, this action is more marked.

S.

EXHAUSTION OF THE SOIL OF GREAT BRITAIN,

[FROM THE LONDON QUARTERLY REVIEW.]

The enormus corn-imports, and the continual rising prices of those kinds of farming produce which cannot be readily imported, demand an examination into the state of our agriculture, and may, perhaps, justify an attempt to point out the causes of the increased cost of produce and of the diminished growth of corn.

A quantitative analysis of our past and present corn-growth cannot be obtained, but there is ample evidence to show that the production of grain reached a culminating point immediately after the repeal of the corn laws, and that it has subsequently steadily declined, the yearly average growth having been about three million quarters of wheat less in the past ten years than in the ten years ending 1851; while the value of the increase in corn-imports, including nearly five and one-third millions of quarters of wheat, has been about 20,000,000l. a year at the average prices. The agriculture of the United Kingdom maintained, so far as wheaten bread is concerned, an average of about five millions less in the past ten years than in the ten years ending 1841, taking six bushels of wheat per head as the accepted standard of consumption, instead of the old eightbushel standard which was established on data collected in the last century, when less meat and vegetables were consumed than at the present time. (Note 1.)

We do not question the advantage of buying in the cheapest market, and of obtaining from abroad what our fields have failed to produce; but as the results shown in the table marked (Note 2), coupled with the insufficient supply of wheat, have disappointed the expectations of thirty years ago, in reference to the improvements of scientific farming, it will not be inopportune to inquire into the defects of English agriculture.

We may here remind our readers that there are two schools of scientific agriculture. Baron Leibig and his followers maintain that the land is becoming exhausted by our system of modern farming, which does not return to the soil the residuum of the crops produced by it; while agricultural writers generally declare that the soil possesses a natural and inex. haustible store of plant food, which can be made available by tillage and the use of solvents.

No two schools of philosophy were ever more completely opposed than the idealists and realists of agriculture, whose rival doctrines raise the im

portant practical question whether the future development of agriculture may be sought ab intra, that is, by tillage and stirring the soil, or ab extra, by manuring it; and we may add that, until the opposite theories of agriculture, in regard to the inherent qualities of the soil, are reconciled, the public can hardly expect to be well advised on such important subjects as the sewage question, and the practicability and method of dealing profitably with our 31,000,000 acres of wastes.

We propose in the present article to consider, first, the history of price and production; and, secondly, the exhaustion of soils and means of restoration.

The evidence on the first part of our subject points to the existence of recurring cycles of good and bad harvests, and if it is insufficient to establish the fact of regularity in the alternation of favorable and inclement periods, it does, we think, conclusively prove that certain cireumstances in regard to the prevailing weather, and the consequent yield of crops, are curiously repeated in the history of agricultural production.

The records of the Merton College estates enabled Mr. Rodgers to ascertain that abundant harvests were continuous from 1321 to the incidence of the Great Plague (1318). The first seventy years of the fifteenth century were still more abundant, so that during great part of the civil wars between the houses of York and Lancaster corn was remarkably cheap.

In the sixteenth century, the number of " sturdy beggars," idle persons, "vagabonds," and "rufflers," who could not be cured by whipping and the stocks, was increased by a dearth. There were also so many deficient harvests in the next century during the Parlimentary war, and until the year 1655, that corn was remarkably dear, and there was an end to the use of wheaten bread for a time among the poor; and peas, beans, and even acorns were occasionally mixed with the grain before grinding it. At the expiration of another hundred years, Arthur Young found, in his "Tours," that wheaten bread was again common everywhere, except among the well-paid laborers of the north, who still retain a taste for oatmeal cakes and porridge. The prevalence of a wheaten loaf at every period of English history, in all but exceptional cases, is inconsistent with the common but erroneous idea that our climate is unsuited to the wheat crop, which is, in fact, nowhere more secure than in England. The epoch of abundance in the eighteenth century commenced about the year 1715 and ended in 1765, the only years of marked deficiency in this series being in 1727, 1728, 1740, 1756 and 1757, when the accumulation of old corn checked the rise in prices; and during this long period, laboring people once more obtained the same command over the necessaries of life which they had possessed in the early days of medieval agriculture, when their