When zinc is dissolved by an acid, a black powder is precipitated, which has been thought to consist of the carbonat of iron: but M. Proust conjectures it to be a compound of arsenic, copper, and lead; he also supposes that zinc usually contains iron and magnesia. Zinc appears to be capable of forming only one oxyd, with whatever metal it may be combined, or in whatever acid it be dissolved.

These are the principal topics detailed in this valuable memoir; they convey important information on some very interesting parts of chemical science; the experiments are simple, but decisive; and the whole is marked by that acuteness which so eminently distinguishes the writings of the Spanish philosopher.

The next two papers are by M. SABATIER, containing his Report of a memoir of M. Maunoir on the organization of the Iris, and the operation for forming an artificial pupil, when by accident the natural aperture has been closed.-M. Maunoir conceives that he has detected in the iris two distinct sets of fibres, one radiate and the other circular; these latter composing the inner part of the aperture. We are scarcely able, from the abstract here presented, to conclude how far we may depend on the observations; similar opinions have been supported by former anatomists, but have afterward been abandoned as

untenable.

Report of a Committee appointed to examine the Experiments of M. Achard, respecting the Sugar contained in the root of the Beet. By M. DEYEUX. This interesting paper commences with an account of the different experiments that have been instituted for the purpose of obtaining sugar in France, first by attempting to naturalize the cane, and afterward by planting the sugar maple. The cane acquired a sufficient size, and seemed to grow with vigor: but it was found that its juice was not so far matured as to contain the due proportion of saccharine matter; and with respect to the maple, the expense attending its cultivation renders its use inadmissible. Margraff had long ago shewn that the beet contained a very pure sugar: but he had not estimated its quantity with sufficient accuracy to enable him to point it out as an economical concern. was lately done by M. Achard, who published a set of experiments on the subject; and who concluded from them that a pure sugar might be obtained from the beet at a moderate expense. The committee divide their remarks into three heads: in the first, they attempt to ascertain the exact quantity of sugar that is contained in the beet root; in the second, they examine the process recommended by Achard; and in the third, they endeavour to improve on this process.

This

In order to ascertain the proportion of sugar in the beet, a quantity of the roots was cut into small pieces, and digested for some time in alcohol; the latter being evaporated, the sugar was formed into a crystallized mass, while a substance like melasses was left behind. The proportion of sugar obtained was very considerable: but a process, in which a large quantity of alcohol is employed, could never be recommended as an economical method of forming sugar. The plan adopted by M. Achard was to boil the roots, then to break them down into a pulp, and afterward to successively strain and evaporate until all the sugar was separated. The committee imitated this process, and obtained a quantity of good sugar, but less in proportion to the weight of the roots employed than by the former method with alcohol. They also found that the beet sugar, by being refined, lost one-sixth more than the sugar from the cane. They tried a number of experiments with a view to the improvement of Achard's process; especially with the intention of separating from the juice a mucous substance, which seemed to be mixed with it, and to prevent its crystallization: but they were not successful; and the only suggestion which they offer is that the root should not be boiled, but should be rasped down into a kind of pulp. They conclude by endeavouring to form an estimate of the expense at which sugar could be furnished from the beet root; and after having made the necessary allowance, it appears to be somewhat more than the price at which common sugar is usually sold in France. They remark, however, that possibly by culture the juice of the Beet might be rendered more abundant in its saccharine impregnation.

Report on the mode of escaping the Small Pox by the Vaccine Inoculation. By M. HALLE.-This author traces the history of vaccination, from its first discovery by Jenner to its general adoption in France; he describes the appearance and progress of the pustules; and he relates at some length the trials that were instituted to ascertain its preservative power. He afterward notices those circumstances which have produced a want of success in the operation; which he reduces to three heads; first, when the pustule produced does not exhibit the characters of the true disease; secondly, when deseases have succeeded which have been thought to be the small pox, but were not so in reality; and lastly, when the small pox has been deve loped at the same time with the vaccine, in consequence of the patient having been previously exposed to the contagion. The paper contains much useful matter: but the subject has been so fully discussed in this country, and is so generally understood, that we shall not dwell on it.

7

MEMOIRS.

MEMOIRS. Second Memoir on the Physical Structure of the Hill of Montmartre, and other corresponding hills. By M. DESMAREST. -The quarry of Montmartre exhibits a great number of regular, prismatic strata of the gypseous or marley earths, which the author here describes with considerable minuteness. In a former memoir, he had explained his ideas respecting the manner of their formation by gradual subsidence; and he endeavours to shew that the actual appearances correspond with his hypothesis. The English reader will be somewhat amused, and probably puzzled, with the names given by the workmen to the different layers; many of which bear but a very remote resemblance to the objects from which they have received their denominations.

Second Memoir on the Anomaly which takes place in the change of bases of two Salts by levering the temperature. By M. GuyTON.-It had been observed by Scheele that, when the solutions of the sulphat of soda and the muriat of magnesia were mixed together at an ordinary temperature, no particular effect ensued: but that, if the mixture was cooled below the freezing point, a mutual decomposition took place, and the new compounds remained permanent, although the temperature was again elevated; and there are other salts which exhibit the same phænomena. The effect is obviously produced by the extrication of caloric; it has been ascribed to the expansive force of freezing water: but this supposition cannot be admitted, because the decompostion takes place before the freezing commences, and in course before the change of bulk is produced. M. GUYTON endeavours to explain the effect by supposing that, in consequence of the passage of the caloric out of each molecule of salt, a motion is produced; and the external parts, which first become cooled, not exercising so much pressure on the internal, leave them to form new compounds; when, as in the case before us, the quiescent and divellent affinities were previously almost exactly balanced.

Memoir on the method of preparing Morocco Leather at Fiz and Tetuan. By M. BROUSSONET.This substance is formed from the skins of goats; and the best kind is manufactured at Fez. Before the skins undergo the operation of tanning, they are stained with cochineal and alum. The tan is procured from the bark of a native tree, the botanical characters of which do not appear to be accurately ascertained. One part of the process consists in keeping the skins immersed for some time in water, with a quantity of unripe figs. The yellow morocco is dyed with the pomegranate rind and alum.

On the Decomposition of the calcareous Marine Salts, by means of lime, fixed alkali, and volatile alkali. By M. BAUMÉ.-There

appears

appears to us very considerable confusion in this paper, arising probably in part from a want of precision in the terms employed. The author, however, seems to entertain very peculiar opinions respecting the nature of the earthy bodies ;if we are not deceived in his meaning, he affirms that they may be converted into each other, both by the gradual operation of time and by the process of calcination.

Experiments on a viscid substance which collects on the branches of the Robinia Viscosa. By M. VAUQUELIN.-This substance was found not to be affected either by water or by alcohol, but to be easily soluble in ether. From a consideration of its properties, the author concludes that it differs in some respects from any vegetable substance hitherto examined. In the two next memoirs, we have an account of the plant from which this substance is procured; the first by M. CELS, the second by M. VENTENAT.

Reflections on a disease of Rye, and the dreadful destruction of Trees. By M. ROUGIER LABERGERIE.-In the disease which is here considered, parts of the plant become of a red colour; which is imagined by the author to be produced by cold winds coming on the plants when nearly in blossom, after a moist or foggy spring. He describes the effects of the disease at length, and supposes that it may be in some measure obviated by sowing the land, which is exposed to the north-east, later than is now usually done; and by forming a shelter for it by hedges or plantations. He speaks of the great destruction which the woods of France have lately undergone from various causes, principally depending on the events of the revolution; and he earnestly calls on the government to endeavour to remedy the grievance.

Memoir on the cultivation and economical uses of the Date-bearing Palm. By M. DESFONTAINES.-We have here a long and (as far as we can judge) an accurate description of the properties, culture, and uses of this plant; which, in the number of people to whom it affords nourishment, may vie with any of the corn-bearing tribes.

Reflections on the decomposition of the Muriat of Seda by the Oxyd of Lead. By M. VAUQUELIN.-The fact that common salt may be decomposed by the oxyd of lead, its acid being united to the lead, while the soda is disengaged in a state of purity, has been long known, but has not been very satisfactorily explained. The present author, by carefully examining the results of the operation in its different stages, and after its termination, concludes that the effect is produced in consequence of the affinity of the muriat of lead for an excess of oxyd; this excess of oxyd also rendering the compound insoluble in water,

and

and giving to it the fine yellow colour. Although it be true, however, that a muriat of lead with an excess of oxyd is formed, and that it possesses the properties here ascribed to it, we have some doubt how far it can be supposed to be instrumental in effecting the decomposition.

Experiments on the Oxyds of Lead, especially the Brown Oxyd. By the same. This oxyd is formed by the action of the nitric acid on minium, or by exposing white lead to the oxygenated muriatic acid gas. The properties of the substance are detailed, and we have some experiments to determine the quantity of oxygen in this and the other oxyds of lead. M. VAUQUELIN thinks that Bergmann and Klaproth have estimated the quantity of oxygen in white lead too highly, and that it contains only 7 per cent. ; the oxygen in the red he calculates àt 9; and that in the brown oxyd at 21 per cent.

The next memoir, by M. VILLARS, gives an account of some specimens of Fossil Wood, larch, birch, and aspin, found in the mountains of Lans, at a great elevation.-It appears from their position that these substances could not have been transported to the place in question, and yet there are no woods now found nearly so high. Hence it is rendered probable that the mountains must at some period have been warmer than they are at present; a circumstance which the author principally ascribes to their having been formerly much more covered with forests. The wood was found imbedded in peat; which, together with the low temperature, was probably the cause of its long preservation.

Extract from a Memoir on the Marine of Venice. By M. FORFEIT. This very long paper contains some curious and interesting matter, but we think that it is not of a nature exactly suited to the collection in which it is inserted. It gives a very particular account of the geographical situation of Venice, its marshy islands or lagunes, its canals, the method which is adopted for preserving them in order, the arsenal, the military and civil establishment for the marine, the management of the forests, and the maritime festivals. On each of these topics, the author dwells with much minuteness.

Memoir on the application of the Steam Engine to the drawing of Coals from the Pits. By M. PERIER.-The object of this paper is sufficiently expressed in the title. In order to accomplish it, the author proposes a piece of mechanism, by which, whenever the cylinder is stopped, its motion will be reversed; and in this manner the buckets will be kept alternately ascending and descending, as in the usual way when horses are employed. On a method for superseding the operation of amputating the Arm at the Shoulder Joint. By M. SABATIER.-The author observes that, where the head of the humerus has been fractured,