the animal is held up by its tail, or the part between the anterior extremities of the electrical organs, no shock is experienced. He made an incision round the electrical organs, and even separated them entirely from the body, except that they still communicated by the nerves; and it did not appear that any diminution took place in the power of producing shocks. We are informed that the nerves which are distributed to the electrical organs come from the medulla oblongata.

A Description of a Process, by which Corn tainted with Must may be completely purified. By C. Hatchett, Esq. F.R.S.-It is probable that many of our readers may have already seen an account of Mr. Hatchett's process, since, in consequence of its great practical importance, pains were taken to make it publicly known: but we shall quote it in the ingenious author's own words:

The wheat should be put into any convenient vessel capable of containing at least three times the quantity, and the vessel is to be subsequently filled with boiling water; the grain should then be occasionally stirred, and the hollow and decayed grains (which will float) may be removed; when the water has become cold, or in general when about half an hour has elapsed, it is to be drawn off. It will be proper then to rince the corn with cold water, in order to remove any portion of the water which had taken up the Must; after which the corn, being completely drained, is without loss of time to be thinly spread on the floor of a kiln, and thoroughly dried, care being taken to stir and to turn it frequently during this part of the process.'

Observations on an astringent vegetable Substance from China. By W. T. Brande, Esq. Sec. R.S. The bodies which Mr. Brande examined were irregular vescicles, about one-tenth of an inch in thickness, of a greyish red colour and very brittle; some of them were adhering to the young twigs of a tree. The same substance appears to have been described by Du Halde. They have a remarkably astringent taste, and seem to possess all the properties of tan in a very high degree. Distilled water took up three-fourths of the whole substance; and, when the fluid was evaporated, a brown transparent residuum was left, having a resinous fracture, a rough, astringent, and sour taste, and which powerfully reddened litmus paper.' It was perfectly soluble in alcohol, as well as in water, and seemed to consist of tan of a particularly pure quality. A small part of what was left by the water was diesolved by alcohol, and was considered as a resin; the remainder exhibited the characters of the simple woody fibre. The aqueous solution procured in the first instance appeared to contain no extract, but gave obvious indications of gallic acid. Mr. Brande succeeded in obtaining this acid in a state

of considerable purity, by boiling pure caustic lime in a strong infusion of the galls, and adding to it, when cold, oxalic acid, by means of which the lime was precipitated. When the

Chinese galls are distilled, a quantity of liquid gallic acid is obtained tolerably free from admixture. Mr. Brande observes that the tanning principle in these galls is soluble in alcohol; and he remarks that the assertion of many chemical writers concerning the insolubility of pure tannin in that menstruum is not correct.' He also particularly notices the experiments of M. Bouillon La Grange, and concludes that the tannin which that gentleman used must have been impure. It must, however, be stated that the alcohol employed by Mr. Brande was only of the specific gravity of 820, and still therefore contained a quantity of water, which might affect the result. With respect to the probable use of the substance in question, we shall transcribe the paragraph with which the paper

concludes.

The want of extractive matter in the China galls, would probably render them very unfit for the purposes of tanning, and I do not find from Du Halde, that they are ever applied by the Chinese to that use. I found the leather produced by their infusion extremely brittle when dried. The same circumstance however, namely, the absence of extractive principle, probably would materially contribute to their excellence as a source of the black dye, the intensity and perfection of which is, I conceive, often interfered with by the presence of extractive matter in the common gall nut and other vegetable astringents usually employed. These galls are likewise particularly proper for the production of writing ink, the tendency of which to become thick and mouldy seems principally to be derived from extractive

matter.'

Some Researches on Flame, By Sir H. Davy, LL.D. F.R.S. &c.—The author had shewn, in some former papers, that the explosion of highly combustible gaseous mixtures required a powerful heat to produce their combustion, and that the effect might consequently be prevented by inclosing them in the wire-gauze tissue, which, although permeable to light and air, cooled the gas in its passage through the orifices. The beautiful application of this principle to the preservation of the lives of the miners, in those collieries in which inflammable air prevails, is well known, and cannot be too highly appreciated.

In his continued researches on the subject of flame, Sir H. Davy found that the intensity of the light depends principally upon the production and ignition of solid matter in combustion, and that the heat and light in this process are in a great measure independent phenomena.' He has since that time still farther pursued the subject, and the present paper

contains

contains the results of his investigations.

remarks into four heads:

He divides his

In the first,' he says, 'I shall discuss the effects of rarefaction, by partly removing the pressure of the atmosphere upon flame and explosion. In the second, I shall consider the effects of heat in combustion. In the third, I shall examine the effect of the mixture of gaseous substances not concerned in combustion upon flame and explosion. In the fourth, I shall offer some general views upon flame, and point out certain practical and theoretical applications of the results.'

He found, in reference to the first of these objects of inquiry, that a jet of hydrogen from a small glass-tube was no longer capable of burning in air that was rarefied six times, but that, when the jet was made larger, the rarefaction might be continued to ten times. As in the latter instance the point of the tube was rendered of a white heat, and the gas continued to burn as long as the tube remained red-hot, the author was induced to suppose that the combustion ceased, not from the deficiency of oxygen, but from the want of a due degree of heat; and he was confirmed in his opinion by the issue of a number of experiments, which shewed that those bodies, which require the least oxygen for their combustion, are such as evolve most heat. The conclusion to which Sir H. Davy was led by the results of his experiments is contrary to the opinion of M. de Grotthus on this subject, who supposed that rarefaction destroys the combustibility of gaseous substances; and the same effect ensues, whether the rarefaction be produced by removing the atmospherical pressure or by heat. M. de Grotthus, from an experiment which seems to be obviously incorrect, inferred generally that expansion by heat destroys the explosive power of gases; whereas Sir Humphry's experiments, which seem to be unexceptionable, lead him to conclude that they explode at a lower temperature when expanded by heat. It had been supposed by many eminent chemists, and among others by M. Berthollet, that, when heat or the electric spark is employed to produce an explosion in a gaseous compound, the compression arising from the sudden expansion of the heated portion is the cause of the effect: but Sir H. Davy's experiments induce him to take a different view of the subject. It would appear,' he says, 'then, that the heat given out by the compression of gases is the real cause of the combustion which it produces, and that at certain elevations of temperature, whether in rarefied or compressed atmospheres, explosion or combustion occurs, i. e. bodies combine with the production of heat. and light.'

In the third part of his paper, the author considers the effects of the mixture of different gases in explosion and combustion; for which purpose he made a series of experiments, evincing that an explosive compound of two volumes hydrogen and one volume oxygen is differently affected by the mixture of a certain quantity of other gases; or that the proportion of these gases necessary to prevent the explosion is different in each particular case. Their operation in this respect seems to bear no ratio to their density, or their capacity for heat.

Thus nitrous oxide, which is nearly denser than oxygene, and which, according to De la Roche and Berard, has a greater capacity for heat in the ratio of 1.3503 to .9765 in volume, has lower powers of preventing explosion; and hydrogene, which is 15 times lighter than oxygene, and which in equal volumes has a smaller capacity for heat, certainly has a higher power of preventing explosion; and olefiant gas exceeds all other gaseous substances in a much higher ratio than could have been expected from its density and capacity.'

The conclusion deduced from these experiments is that

The power of elastic fluids to abstract or conduct away heat from solid surfaces, is in some inverse ratio to their density, and that there is something in the constitution of the light gases, which enables them to carry off heat from solid surfaces in a different manner from that in which they would abstract it in gaseous mixtures, depending probably upon the mobility of their parts. The heating of gaseous media by the contact of fluid or solid bodies, as has been shown by Count Rumford, depends principally upon the change of place of their particles; and it is evident from the results stated in the beginning of this section, that these particles have different powers of abstracting heat analogous to the different powers of solids and fluids. Where an elastic fluid exerts a cooling influence on a solid surface, the effect must depend principally upon the rapidity with which its particles change their places: but where the cooling particles are mixed throughout a mass with other gaseous particles, their effect must principally depend upon the power they possess of rapidly abstracting heat from the contiguous particles; and this will depend probably upon two causes, the simple abstracting power by which they become quickly heated, and their capacity for heat which is great in proportion as their temperatures are less raised by this abstraction.'

In the fourth section, Sir Humphry recurs to his opinion, already stated, of the nature of flame; and of the cause which prevents it from being made to pass through the wire-gauze, depending on the metallic substance of which the gauze is composed cooling each portion of the elastic matter that passes through it, so as to reduce its temperature below the degree at which it is capable of becoming luminous: by which means the temperature is kept below the exploding point. The

author

author gives many illustrations of this doctrine; shewing how different inflammable bodies, in proportion to the temperature at which their combustion takes place, require a gauze of different degrees of fineness. A much finer mesh is necessary to prevent the explosion of a mixture of oxygen and hydrogen than of the fire-damp, which is fortunately the least combustible of the known inflammable gases.'

Sir Humphry makes an application of his principles to luminous meteors, which we confess appears to us not worthy of the other parts of the paper. He imagines that what are called falling stars may be small solid bodies moving round the earth in very excentric orbits, which become ignited only when they pass with immense velocity through the upper regions of the atmosphere;' and that the meteoric bodies, which throw down stones with explosions, may be similar bodies which contain either combustible or elastic matter.'

He

Some new Experiments and Observations on the Combustion of gaseous Mixtures; with an Account of a Method of preserving a continued Light in Mixtures of inflammable Gases and Air, without Flame. By the Same. This paper may be regarded as a kind of appendage to the preceding, but contains some of the most interesting and curious of all the experiments that have been performed by this chemist, who is equally distinguished for his industry and his genius. had observed, in his researches on flame, that oxygen might be made to combine both with hydrogen and charcoal at a temperature below that of a red heat, and in course below that which produces explosions; and it seemed to him probable that the heat given out, during these combinations, might be sufficient to turn a metallic wire to redness. The conjecture was verified by experiment; he plunged a lamp into a mixture of atmospherical air and carburetted hydrogen, which extinguished the lamp; and he found that a platinumwire, held over the lamp, became red-hot, which effect is produced by the heat evolved during the silent combination of the gases composing the mixture. He also observed that the vapour of ether and other inflammable liquids possessed the same power of silently combining with the oxygen in the air of the atmosphere, and evolving so much heat as to redden a platinum-wire. From this elegant experiment, he draws the following practical application:

By hanging some coils of fine wire of platinum, or a fine sheet of platinum or palladium above the wick of his lamp, in the wire-gauze cylinder, the coal-miner, there is every reason to believe, will be supplied with light in mixtures of fire-damp no longer explosive; and should his flame be extinguished by the

S 4

quantity