not appear that any superfluity of hydrogen occurred. The general conclusion, which Mr. Davy deduces from this part of his experiments, is that by the operation of potassium upon ammonia, it is not a metallic body that is decompounded, but the volatile alkali, and that the hydrogene produced does not arise from the potassium, as is asserted by the French chemists, but from the ammonia, as I have always supposed; the potassium in the most refined experiments is recovered, but neither the ammonia nor its elements can be reproduced, except by introducing a new body, which contains oxygene and hydrogene.'

Precisely the same observations apply to the metal of soda; and, as it is less violent in its action, the phænomena can be better ascertained than in the corresponding processes with pot

assium.

The author next examines the opinion of Mr. Ritter, who also imagines that hydrogen is essential to the existence of the alkaline metals. He draws that inference from their specific levity, but to this argument we have the following very satisfactory reply: Sodium absorbs much more oxygen than potassium, and on the hypothesis of hydrogenation, must contain much more hydrogen; yet though soda is said to be lighter than potash, in the proportion of 13 to 17 nearly, yet sodium is heavier than potassium in the proportion of 9 to 7 at least.' Mr. Ritter likewise endeavours to support his opinion by a curious circumstance which he first noticed, respecting the effect of galvanism on tellurium. When this metal is placed in the circuit, oxygen is discharged at the positive surface; while at the negative side a compound is formed, which appears to consist of the metal and hydrogen, or to be a proper hydruret of tellurium. The fact may be considered as sufficiently established, but it does not appear that any inference or analogy can be drawn from it to the other metallic bodies. As potassium and tellurium exhibit a strong attraction for each other, it seemed probable that potash might be decomposed by permitting heated charcoal to act at the same time on a mixture of potash; and the oxyd of tellurium; and it was accordingly found that, by these means, an alloy of potassium and tellurium was produced, of which the leading properties were very similar to those of sulphuretted hydrogen. An alloy of a somewhat similar nature, though less perfect in its composition, was formed by the oxyd of arsenic and tellurium; a circumstance which Mr. Davy was led to predict, from the known affinity which arsenic possesses for hydrogen. With respect to the nature of the metals from the fixed alkalies, he conceives himself warranted in still retaining his original

idea. After these illustrations,' he says, I trust the former opinions which I ventured to bring forward, concerning the metals of the fixed alkalies, will be considered as accurate, and that potassium and sodium, can with no more propriety be considered as compounds, than any of the common metallic substances; and that potash and soda, as formed by combustion of the metals, are pure metallic oxids, in which no water is known to exist.'

We have next a section containing a number of experiments on nitrogen. From some circumstances attending the action. of nitrogen on ammonia, it might be supposed that the former of these substances was a compound; and either that it consisted of oxygen and hydrogen, or that it might be produced from water. The Professor has bestowed much pains on the solution of this problem, but hitherto without success; in all these processes, when nitrogen was evolved, he saw no sufficient ground for believing that it had been either generated or decomposed. In some of the processes in which it has been supposed to have been formed, as in those of Dr. Pearson on the electrization and of Dr. Priestley on the freezing of water, the nitrogen disengaged may be traced to some accidental circumstance. Mr. Davy attempted to decompose it by permitting nitrous gas and sulphuretted hydrogen to act on each other, by electrifying potassium and the phosphuret of lime in nitrogen gas, and by passing nitrogen gas and oxyge nated muriatic acid-gas through heated tubes: but in no case were any decisive results obtained; and nothing occurred, in any of these experiments, which can be considered as proving the decomposition of nitrogen.

Some experiments on ammonia are next given, particularly on the proportion in which hydrogen and nitrogen enter inta its composition; and also respecting the existence of oxygen as This latter question cannot yet be one of its constituents. considered as decided, though the evidence appears to preponderate against the existence of oxygen:

'On the whole.' says the author, the idea that ammonia is decomposed into hydrogene and nitrogene alone, by electricity, and that the loss of weight is no more than is to be expected in processes of so delicate a kind, is in my opinion, the most defensible view of the subject.

But if ammonia be capable of decomposition into nitrogene and hydrogene, what, it will be asked, is the nature of the matter existing in the amalgam of ammonia? what is the metallic basis of the volatile alkali? These are questions, intimately connected with the whole of the arrangements of chemistry; and they are questions, which, as our instruments of experiment now exist, it will not, I fear, be easy to solve.'

A section

A section follows on the metals of earths. It principally consists of a detail of experiments which were made for the purpose of forming alloys with potassium and the metallic bases of the common earths, and amalgams from those metals and mercury. The paper concludes with some hypothetical considerations. It is remarked that hydrogen combines with more oxygen than any other substance, that therefore it must be more highly positive than any other substance, and that consequently, if it be an oxyd, as has been conjectured, no simple attraction can decompose it. At present, it seems rather doubtful whether the recent discoveries of Mr. Davy be favourable to the antiphlogistic hypothesis, or whether they do not rather lead to the conclusion that hydrogen is the common principle of inflammability. We are disposed to the former opinion, though it is probable that the theory will require some modifications before it can be adopted.

The Case of a Man, who died in consequence of the Bite of a Rattlesnake; with an Account of the Effect produced by the Poison. By E. Home, Esq., F.R.S.-Readers of news-papers will recollect that the subject of this case, a journeyman carpenter, having irritated a rattle-snake which was exhibited in Piccadilly, was severely bitten by it. He went almost immediately to St. George's hospital, where the arm was found to be considerably swelled and painful, the surface of the body was cold, and a degree of delirium prevailed, with sickness at the stomach. Ammonia was applied to the wound, and was given internally in combination with ether. In a few hours, the pain and swelling were much increased, faintings came on, the skin was very cold, and the pulse frequent. On the following day, the arm exhibited the symptoms of incipient gangrene, the skin became livid and mottled, and vesications began to be formed. The process of mortification slowly advanced, until sloughing took place; and the patient died on the 18th day. The case is related with minuteness, and no doubt with accuracy. From comparing it with others. of which we have authentic accounts, it would appear that very different effects are produced according to the size of the wound, or the force with which it is inflicted. Sometimes, the shock is so great as to prove almost immediately fatal; and in this case the only morbid appearance, discoverable on dissection, consisted in the destruction of the cellular membrane round the bite, and the inflammation of the contiguous muscles. Mr. Home does not think that any internal remedy can counteract the effects of the poison, and of course he has no faith in the supposed specific, the eau de luce. We subjoin, in his own words, the treatment which he recommends; pre

mising,

mising, however, that we can scarcely regard it as likely to prove very efficacious.

The only rational local treatment to prevent the secondary mischief, is making ligatures above the tumefied part, to compress the cellular membrane, and set bounds to the swelling, which only spreads in the loose parts under the skin; and scarifying freely the parts already swoln, that the effused serum may escape, and the matter be discharged as soon as it is formed. Ligatures are employed in America, but with a different view, namely, to prevent the poison being absorbed into the system.'

An Analysis of several Varieties of British and Foreign Salt (Muriate) of Sada, with a View to explain their Fitness for different economical Purposes. By W. Henry, M.D. F.R.S. &c.Although the object of this paper is rather economical than scientific, yet it is a point of so much importance, that we are glad to see it taken up by a person who is so capable of doing it justice. It has been frequently asserted that foreign salt, prepared by the spontaneous evaporation of sea-water, is preferable, for the purposes of preserving food, to the salt which is manufactured by artificial heat in various parts of this island. Dr. Henry proposes to inquire whether there be any real foundation for this preference, whether any chemical differences can be detected between the, several kinds of salt, and if so in what these differences consist, and lastly, whether all the varieties of British salt are equally proper as preservatives of food. He commences by briefly describing the several processes that are employed in this country, especially those which are adopted in Cheshire and Lancashire, in the neighbourhood of Edinburgh, and at Lymington. In Cheshire, the salt is prepared from salt-rock or brine springs, entirely by artificial heat; and principally in consequence of the degree of heat employed, it is formed into the several varieties of stoved salt, common salt, large grained flaky salt, and fishery-salt, the first being produced by the highest and the last by the lowest temperature. The same kind of processes are pursued on the banks of the Mersey. The stoved salt is in small crystals, and is preferred for domestic purposes; and the common salt is used for curing provisions which are not intended for long voyages, while for this purpose the fishery-salt is selected. In Scotland and Hampshire, salt is prepared by the evaporation of sea-water, in the former altogether by artificial heat. The salt usually called Bay-salt is procured entirely by the spontaneous evaporation of sea-water.

After these preliminary observations, Dr. Henry proceeds to give us his analysis of the different kinds of salt. The results of his experiments are placed in a tabular form; exhibiting the

proportion

proportion of insoluble matter, that of the muriate of lime and of magnesia, that of sulphate of lime and of magnesia, and lastly the proportion of the pure muriate of soda. The author's deductions from these experiments are, that the foreign baysalt is purer, generally speaking, than salt which is prepared by the rapid evaporation of sea-water; but that it is contaminated with about three times the amount of impurities, discoverable in an equal weight of the Cheshire large-grained salt, and with more than twice that of those that are found in the stoved and common salt of the same district.' The insoluble matter, which probably consists in a great measure of accidental impurities, is much greater in the foreign bay-salt than in any other species: more muriate of magnesia occurs in the Scotch than in the bay-salt, but very little of it is found in the Cheshire salt; the salt-rock, from which the Cheshire salt is manufactured, being almost entirely free from this ingredient. The sulphate of lime exists in the greatest quantity in the Scotch, and least in the Cheshire salt; and from this latter the sulphate of magnesia is totally absent, though it exists in considerable proportion in the others. Besides the saline ingredients which enter into these several varieties, Dr. Henry conceived it to be an object deserving of inquiry whether they might not possess different quantities of the water of crystallization. It was found, however, that, when they were equally dry, the proper water of crystallization existed in a very small quantity in any of them; that the fishery and the bay-salt, as we might expect from their larger crystals, contain the most, and that stoved salt supplies the least water. On what, then, it may be asked, does the different effect of these varieties of salt depend? To this question, the author proposes the following

answer:

If I were to hazard an opinion, on a subject about which there must still be some uncertainty, it would be that the differences of chemical composition, discovered by the preceding train of experiments in the several varieties of culinary salt, are scarcely sufficient to account for those properties, which are imputed to them on the ground of experience. The stoved and fishery salt, for example, though differing in a very trivial degree as to the kind or proportion of their ingredients, are adapted to widely different uses. Thus the large grained salt is peculiarly fitted for the packing of fish and other provisions, a purpose to which the small grained salts are much less suitable. Their different powers, then, of preserving food must depend on some mechanical property; and the only obvious one is the magnitude of the crystals, and their degree of compactness and hardness. Quickness of solution, it is well known, is pretty nearly proportional, all other circumstances being equal to the quantity of surface exposed. And since the surfaces of cubes are as the squares of their sides, it should follow that a salt whose crystals are of a given magnitude will

8

dissolve