An excellent Method of draining Wet Land to render it fit for Culture. From the ANNALES DES ARTS ET MANUFACTURES, Low lands, as well as meadows, may be drained, if not all at once, at least by degrees. In the first place, pits must be dug in the lowest places, of four or five feet wide, and seven or eight feet deep. The earth thrown upon the sides to be afterwards spread over the surface, and to raise it a little. As many holes may be dug as we choose, because the more there are of them, the more rapidly the land drains. From one pit to the other are dug small ditches, from two to three feet wide, and four or five feet deep. The pits and ditches are heaped to a certain height, which is determined by the state of the soil, with rough pieces of stone, so that the water may filter through the interstices. Above this bed of irregular stones is placed a base of flat stones, which is covered with the earth taken from the excavations. The soil can then be cultivated as before. Method Method of preparing the Branches of Hops for spinning. From the ANNALES DES ARTS ET MANUFACTURES. AFTER the hops are gathered, the branches are cut into strips, of the length of three ells; they are exposed to macerate in the dew for a few nights, then in running water, and are afterwards dried in the air. They are beaten and crushed, and then treated in the same manner as flax. The cloths made from this material are stronger than those made from flax or hemp. Method of preserving Asparagus for the Winter. From ARCHIVES DES DESCOUVERTES, &c. CUT off the lower part of the asparagus, and boil them in water, in an earthen vessel or tinned saucepan. As soon as the water boils, the asparagus is to be put into it, being previously well washed: the vessel is afterwards to be taken from the fire, covered with a napkin, folded into several doubles, and left at rest for an hour. Then put the asparagus to drain in a sieve, envelope them in another linen cloth, and put them in a place where the sun cannot penetrate, in order to cool, and finish drying them. In the mean time boil some salt in water, and when this solution is cold, put the asparagus into glass or earthen bottles, and moisten it with the salt water. To prevent the contact of the air, cover the surface of the bottles with fat. When the asparagus is wanted for use in the winter, put it into water, and eat it like fresh asparagus. On On Tannin, and on some new Combinations of the Gallic Acid with Vegetable Substances. By M. PELLETIER. From the ANNALES DE CHIMIE. TANNIN is one of the substances which have most exercised the sagacity of chemists. A collection of the different memoirs that have been published on this subject would fill several volumes. Yet, notwithstanding the numerous works of Séguier, Deyeux, Proust, Davy, and several other chemists, we have no clear ideas upon this matter; the most able professors find themselves embarrassed when they have occasion to speak of this immediate principle of vegetables. We are astonished when, in the works of the learned gentlemen I have mentioned, we find properties so different attributed to the same body. And, indeed, the tannins obtained by the processes which have been successively proposed have been different in most of their properties. They have in common only, the faculty of uniting with several animal substances, of forming with them combinations almost insoluble, and which are not susceptible of putrefaction; they have, besides, all of them the faculty of precipitating, in a manner nearly similar, the same metallic solutions; but they are different in taste, colour, solubility in water, &c. &c. We may say, therefore, that pure tannin is not known, or rather that it does not exist. The properties that have been attributed to it, and by which it has been attempted to distinguish it, belong to several of the combinations which vegetables form of themselves. I doubt not, but that if the learned chemists, who have been engaged upon tannin, had considered it as possible to be a com bination bination, they would have discovered the true nature of the tannin matter. Why do they continue to consider this matter as an immediate principle? is it because it precipitates several metallic oxyds from their solutions? but most of the extracts have this property, and it is known that the extracts are at the least triple combinations of acid, of colouring substance, and of vegeto-animal matter. Is it because the precipitates that form the tannin matter in these solutions are gifted with constant, and often lively and brilliant colours: but if it is considered that the gallic acid always accompanies the tannin, and that the colour of the precipitates furnished by the tannin matters in the metallic solutions are the same as those that are manifested by the addition of the gallic acid in the same metallic solutions, might we not then conclude with M. Thenard, ("Memoire de la Société d'Arcueil,”) that the colour of its precipitates is owing to the gallic acid, which, according to this philosophy, can never be entirely sepa rated from the tannin, and which I regard as one of its constituent parts? will this be the property that tannin possesses of combining with animal matters, and of preserving them from putrefaction? But numberless combinations of vegetable matter possess this property, and not to speak of the astringent matters formed by the action of the mineral acids upon the charcoal in several vegetable matters, without referring to the fine experiments of M. Chevreul upon hematine, which in several of these combinations acquires this property, I shall venture to give some observations that I made while employed on * * This chemist has told me that he no longer believes in the existence of tannin. The Analysis of Gall-Nuts, which he is on the point of publishing, will, without doubt, remove the uncertainty which still exists respecting this matter. VOL. XXV.-SECOND SERIES. Rr the the analysis of the juice of hypocistes, and which tend to prove that the gallic acid can combine with several vegetable matters, and thus acquire the properties of tannin. If some gallic acid be poured into a solution of pure gelatine, no precipitate is formed, neither does this acid produce any cloud in gummy solutions; but the union of these substances cannot take place until the liquor be troubled by the formation of numberless white flakes, which at length precipitate. Among these pharmaceutical extracts there are a great number which contain no astringent principles, and which form no precipitate in the solution of gelatine; but by the addition of a certain quantity of gallic acid they acquire this property. The same phenomenon does not occur with the other vegetable acids, which seem, on the contrary, to oppose the precipitation of the gelatine. We know that pure gallic acid forms no precipitate in the solution of sulphate of iron at the maximum, but fixes a fine deep blue in it. The infusion of gall nuts, on the contrary, produces a precipitate in it which is attributed to the tannin; but the gallic acid itself acquires the property of precipitating in part the iron of this solution when associated with extractive matters. Most of the vegetable infusions act with the gallic acid and gelatine like the extractive substances, and the reason is plain; the phenomenon is very evident with the -infusion of saffron made cold. The properties of these precipitates ought not to be absolutely identical; they ought to differ according to the nature of the substances that enter into each combination that formed by gum arabic, gelatine, and gallic acid, is the only one that I have hitherto been enabled to examine; it varies from the others by its extreme ad herence |