even introduced by imbibition a deliquescent salt, such as the muriate of lime, which retains moisture powerfully, as is well known, and seems to have the power of giving a remarkable degree of suppleness to wood. The experiments, contrived to show the effects of deliquescent salts, were made upon deal, which is allowed to be one of the most brittle woods. After having impregnated it with concentrated solutions it was sawed into very thin veneers, some of which I have seen in the possession of M. Boucherie, which after being strongly twisted and bent in various senses, immediately regained their original flatness and evenness when they were left free.

Warping, or shrinking, is occasioned by alternate shrinking and swelling in consequence of varying hygrometric states of the atmosphere. When timber is worked before it is thoroughly seasoned,— and this is apt to happen in regard to pieces of large scantling especially-the shrinking is of course extremely conspicuous when the time necessary to complete desiccation has elapsed. It is this inconvenience which makes it imperative on builders of all kinds, shipbuilders more especially, to keep stocks which necessarily absorb a considerable amount of capital. It has long been a question with engineers to find a remedy for this state of things. Seasoning, indeed, is now effected somewhat more quickly by squaring the logs at the time the trees are cut down; but the loss of time is still very considerable. The mode of seasoning by the stove or vapor has been abandoned as too costly.

After having found that the shrinking and separation of pieces of carpentry did not begin to take place until the timber was upon the point of losing the last third of the moisture which it contained at the time of being cut, M. Boucherie thought that to prevent all warping and shrinking it would be enough to retain this quantity of water in combination with the woody tissue; in other words, to prevent complete desiccation. Facts have proved the correctness of this view. Pieces of wood kept at a certain unchanging degree of moistness by means of a deliquescent salt infused into their pores, do not change their bulk or form, in spite of extreme variations in the hygrometric state of the air. Such pieces of wood, however, exhibit great differences in point of weight under the influence of different circumstances.

Several planks of great breadth and extremely thin were prepared with chloride of lime and joined together; some of them were left unpainted, others were painted on one side, or on both sides; after the lapse of a year these planks were found not to have shrunk or warped, while similar planks of the same thickness and kind of wood, but unprepared, were found to have cast in an extraordinary way."

M. Boucherie has done more than this; he has not only had it in view to preserve wood and to prevent it from warping, qualities so desirable, he has made use of the same faculty of imbibition to im

* Boucherie, op. cit. p. 151.

pregnate the wood with a variety of beautiful colors, and thus to give even the most common kinds tints that will admit of their being used in the construction of costly furniture. The pyrolignite of iron alone gives an agreeable brown tint that harmonizes excellently with the natural color of the harder parts of so many trees which usually resist penetration. By following up the pyrolignite with an infusion of nutgalls or oak-bark, the mass of the wood is penetrated with ink, which presents a black, blue, or gray color, according to circumstances; a solution of another salt of iron succeeded by one of prussiate of potash will cause a precipitate of prussian blue in the wood, &c.; in short, by the numerous reactions of this kind with which chemistry is familiar, a great variety of colors may be obtained.

Among the number of useful properties communicated to wood by impregnation with saline solutions, that of being rendered little apt for combustion ought not to be omitted. M. Gay-Lussac was the first who thought of rendering vegetable tissues incombustible by means of saline impregnations. By incombustible, we are not to understand unalterable by a red heat; for every one must see that the protecting power of no salt can extend so far as this; but tissues which take fire very readily, and burn with great rapidity, cease from giving any flame, and merely smoulder, after they have been impregnated with certain salts; they take fire with difficulty, go out of themselves, become charred, and are incapable of propagating fire. And this is exactly what happens with wood which has been properly charged: it burns, and is reduced to ashes with extreme slowness, so that two huts exactly alike, built one of charged wood, and the other of ordinary wood, having been set fire to at the same moment, the latter was already burned to the ground, when the interior of the former was scarcely charred.†

The ingenious process of impregnating wood by the way of vital inspiration is not without certain objections. In the first place, it can only be performed at those periods of the year when the sap is in motion, and the trees are covered with their leaves. This time, however, is limited to a few months of the year, and the usual practice being to fell timber in the winter, wont and usage are opposed to cutting down trees in the spring and autumn. To meet these objections, M. Boucherie engaged in new experiments, which led him to a means of impregnating timber at all seasons, in winter ås well as spring and autumn, and in a very short space of time; this second method is applicable to wood that has already been squared as well as to the round trunk, provided it has been recently felled.

To impregnate timber by this process, the logs are placed vertically, and the upper extremities are fitted with an impermeable sack for the reception of the saline solution destined to charge them; the fluid enters from above, and almost at the same moment the sap is seen to begin running out below. There are some woods which

* Ann. de Chimie, t. xviii. p. 211, 2e série.

+ Idem, t. lxxiv. p. 152, 2e série.

include a large quantity of air in their tissues; in this case the flow does not go on until this air has been expelled; once begun, it goes on without interruption. The operation is terminated when the fluid, which drips from the lower part, is of the same nature as that which is entering above. In my opinion this method must be preferable to that by aspiration. In the second mode of proceeding, in fact, we accomplish our object by a true displacement; almost the whole of the sap is expelled, and the saline solution introduced has only to subdue or neutralize the very small quantity of soluble organic matter which may remain adhering to the woody tissue. By accomplishing such a displacement by means of simple water we should undoubtedly obtain results favorable to the preservation of timber, inasmuch as we should have freed it from almost the whole of those matters which are regarded as the most alterable themselves, and the first cause of rotting in timber. The rapidity with which the fluid introduced is substituted for the sap which it displaces, and the quantity of this expelled sap which may be readily collected, exceeds any thing that could have been imagined before making the experiment; thus the trunk of a beech-tree about 521 feet in length by 333 inches in diameter, and consequently forming a cube of somewhat more than 29 feet and a half, gave in the course of twenty-five hours upwards of 330 gallons of sap, which were replaced by about 350 gallons of pyroligneous acid. The liquid which penetrates in this way acts so effectually in displacing the sap, that M. Boucherie says we can readily procure or extract by its means the saccharine, mucilaginous, resinous, and colored juices contained in trees. It would, perhaps, be possible, and I beg to suggest this idea to colonial planters, to apply the method of displacement to the extraction of the coloring matters of dye-woods. The trade in dyewoods does not extend beyond localities favorably situated for exportation, so that at a certain distance from the shores of the ocean, or the banks of rivers, it is found absolutely impossible to carry on a trade, the material of which is so heavy and bulky as timber. The greater number of the coloring matters found in wood being soluble, it is possible to export them in the state of extract. Various attempts of this kind have already been made, and if they have not been successful, the obvious cause of this lies in the method which has been followed, and which has hitherto consisted in treating the wood reduced to chips by means of boiling water, and then reducing the colored solution obtained; but it is obvious that in the remote forests of America, or of Africa, where all mechanical means are wanting, nothing but failure could attend upon such a procedure. By the method of M. Boucherie, the main difficulties appear to be got over; there is nothing more to be done, in fact, than to get the trees into the state of logs, and these are generally readily transportable, after which one or more evaporating pans seem all that are further necessary.

Dye-woods.-The greater number of these woods belong to the family of leguminosa; the principal kinds met with in trade are: 1. Mahogany wood, (hæmatoxylon campechianum,) of a reddish

yellow, which becomes brown with age; this wood, besides a variety of alkaline and earthy salts, of volatile oil and unazotized matter, contains a particular coloring principle, called hematine, discovered by M. Chevreul.*

The mahogany grows in the hot intertropical regions of America ; Mexico and some of the West India islands export considerable quantities.

Pernambuco or Brazil-wood is the name given in trade to the trunks of several trees of the genus Casalpinia. The Casalpinia crista of Jamaica, the C. sappan of Japan, the C. echinata of Santa Martha, afford kinds that are very much prized. In point of chemical composition Brazil-wood agrees with Campechy wood; the coloring matter which characterizes it has been named Braziline by M. Chevreul; it is obtained in small crystals of an orange color.

This wood comes to Europe in fagots of about 39 inches in length. Red Saunders-wood is furnished by the Pterocarpus santalinus; it contains a peculiar dye-stuff, santaline, observed by M. Peltier.f

To conclude, the yellow dye-woods of commerce are Fustic, Rhus cotinus, of the family of turpentine trees, a native of the south of Europe, and the Cuba and Tampico woods, which are probably va

rieties of the Morus tinctoria.

OF SUGAR.

'Sugar is met with in almost every part of vegetables; it has been found in flowers, in leaves, in stems, and in roots. It is less abundant in seeds; and it may even be said that the quantity of saccharine matter contained in vegetables in general is invariably diminished at the period of formation of the seed. Sugar, consequently, as well as starch, appears to contribute to the production of the seed.

The very characteristic taste of sugar generally suffices to proclaim its presence; nevertheless, it would be a great mistake a'd we rely upon this character alone for discovering the presence o sugar; several substances possess a very decided sweet taste, without being on that account sugar, in the sense which chemists attach to the name. True sugars, according to chemists, have one property which distinguishes them from all substances with which they may have, in other respects, the greatest analogy; this characteristic property is that of becoming changed, under the influence of water, a suitable temperature, and contact with yeast, into alcohol and carbonic acid. It is certain, nevertheless, that certain bodies which do not belong to the chemical genus, sugar, may, under the influence of fermentation, yield alcohol. I have already quoted starch as coming under this head; but it has been distinctly ascertained, as I have also said, that such substances, under the influence of the ferment itself, are first changed into sugar, which subsequently undergoes the vinous fermentation.

* Chimie appliquée à la teinture, 30e leçon, p. 88.

† Chevreul, Chemistry applied to dying, 30th lecture, p. 94.

It is admitted at the present time that fermentable sugars must be divided into two principal species, in harmony with characters which are most easily appreciated. One of these presents itself in the shape of hard, transparent crystals, and is met with in sufficient quantity to be profitably extracted from the juice of the cane and the beet, the sap of the maple and of certain palms; the other is obtained with some difficulty in the solid state, being most frequently and readily procured in the form of sirup; the taste of this is less sweet, less decided; it exists in the grape and the greater number of fruits. The chemical characters of these two kinds of sugar, which are designated cane-sugar and grape-sugar, are somewhat different; and the elegant researches of M. Biot have shown, that from some of their physical properties, particularly the action of their solutions upon polarized light, they cannot be regarded as constituting one and the same species. In the vegetable kingdom, these two kinds of sugar are frequently met with mixed; and there are certain chemical means which enable us readily to transform cane-sugar into grape-sugar. The inverse transformation has not yet been accomplished; but there is nothing which leads us to conclude that it is impossible; and the time, perhaps, is not very remote when the sugar which is manufactured from potato-starch may be changed into crystallized sugar, similar to that which is obtained from the

cane.

Crystallized sugar. Cane-sugar is readily obtained in large transparent crystals, which are known under the name of sugarcandy. Sugar is fusible under the action of a regulated temperature, it acquires a dark-red color, and passes into the state of caramel; a higher temperature effects its decomposition. It is much. less soluble in alcohol than in water; highly concentrated alcohol, indeed, only dissolves an extremely small quantity of sugar.

M. Peligot's analysis of cane-sugar shows it to be composed of—

Such is the composition of sugar dried at the temperature of boiling water; but the substance, like the majority of organic matters, still contains a certain proportion of constitutional water, which it abandons when it combines with certain bases. Thus sugar combines with oxide of lead, and forms a true saccharate, in which the sugar, deprived of its water of constitution, plays the part of an acid; this combination, which presents itself to us under the form of white mammillated crystals, analyzed by M. Peligot, would indicate the following as the composition of anhydrous sugar