The mode of analyzing these compounds is then described. And here there are some interesting facts to be observed. The action of acids upon the alloys when compared with that which they exhibit on simple steel is amazingly greater. A very small quantity of platina in alloy confers this property, and a greater destroys it. Sir H. Davy had suggested that this action was probably electrical: the whole mass being a series of voltaic combinations. The manner in which our authors reason upon this point, we will exhibit in their own words. Speaking of this action they observe,

"It may be considered as occasioned by the alloying metal existing in such a state in the mass, that its particles form voltaic combinations with the particles of steel either directly, or by producing a definite alloy, which is diffused through the rest of the steel; in which case the whole mass would be a series of such voltaic combinations: or it may be occasioned by the liberation, on the first action of the acid of particles which if not pure platina, contain, as has been shewn, a very large proportion of that metal, and which being in close contact with the rest of the mass, form voltaic combinations with it in a very active state: or, in the third place, it may result from the iron being mechanically divided by the platina, so that its particles are more readily attacked by the acid, analogous to the case of protosulphurit of iron."

"Although we have not been able to prove by such experiments as may be considered strictly decisive, to which of these causes the action is owing, or how much is due to any of them, yet we do not hesitate to consider the second as almost entirely, if not quite, the one that is active. The reasons which induce us to suppose this to be the true cause of the action, rather than any peculiar and previous arrangement of the particles of steel and platina, or than the state of division of the steel, are, that the two metals combine in every proportion we have tried, and do not in any case exhibit evidences of a separation between them, like those for instance which steel and silver exhibit; that when instead of an acid, weaker agents are used, the alloy does not seem to act with them as if it was a series of infinitely minute voltaic combinations of steel and platina, but exactly as steel alone would do; that the mass does not render platina wire more negative than steel, as it probably in the third case would do; that it does not rust more rapidly in a damp atmosphere; and that when placed in saline solutions, as muriate of soda, &c.; there is no action takes place between them. In such cases it acts just like steel; and no agent that we have as yet tried, has produced voltaic action that was not first able to set a portion of the platina free by dissolving out the iron."

We leave this reasoning without comment to the consideration of our readers. In any point of view this peculiar action is highly interesting, especially connected as galvanism

now is, and is every day becoming more so, with a vast number of other phenomena in the natural world.

We will merely proceed briefly to mention, that the fullest practical directions are given for forming and working the alloys in their greatest purity; and their extensive uses are also duly adverted to.

Several other interesting particulars are also brought forward, respecting the difference in the action of the acids on these kinds of steel when hard, and when soft.

Some curious facts are mentioned respecting the action of nitric acid on the powders, resulting after the action of the acids on the alloy. When the alloying metal is one not soluble in nitric acid, a black residuum remains after the alloy has been for some time acted on by other acids, which when washed and dried is found to possess the property, of deflagrating with heat; and with some of the metals, when carefully prepared, is highly explosive.

The paper which is of some length, contains also a great variety of other no less curious facts, observed by these skilful experimenters, who in their endeavours to make science subservient to the uses of art, have thus reciprocally made the progress of art contribute to the extension of science.

No. 24. Experiments and Observations on the Newry Pitch-stone and its Products, and on the Formation of Pumice. By the Right Hon. George Knox, F.R.S.

No. 26. Some Observations on Corrosive Sublimate, By John Davy, M.D. F.R.S.

Neither of these papers, though of considerable importance in regard to some particular chemical questions, are of sufficient general interest to induce us to give an analysis of them.

No. 27. On the State of Water, and aëriform Matter in Cavities found in certain Crystals. By Sir H. Davy, Bart. P.R.S.

This curious and interesting paper has many claims on the attention both of the geologist and the general philosopher. It is in regard to the objects of the former that the author has particularly considered his subject, and he opens his paper with some remarks on the interest attaching to enquiries into the probable manner of the formation of the different rocks; observing that he had often looked for facts or experiments which might throw light on the subject, until on considering the phenomena of certain rock crystals and other siliceous stones containing small cavities, partly filled with fluid, he conceived that they might be examined in a manner so as to afford some important arguments bearing on the

question of the formation of rocks. With this view, therefore, the various specimens which were liberally supplied him from different sources, were subjected to examination.

The following was the mode of conducting the experi

ments:

Holes were drilled in the crystals by the use of diamonds, under distilled water or mercury, the gas was expelled by the introduction of wires, and the fluids included in the cavities were drawn out by means of fine capillary tubes, and experiments were afterwards made to determine the space they occupied which had been accurately measured and marked upon the crystal. In all the experiments it was in the first instance essential to assertain that the crystal was impermeable to the atmosphere. This was tried with an air pump.

In five specimens, the fluid in which they were immersed rushed in the moment they were pierced, and the globule of elastic fluid contracted, so as to appear from six to ten times less than before the experiment.

The fluid was found to be water nearly pure, containing only a minute portion of the alkaline sulphates. The elastic fluid, as well as could be ascertained from the very minute quantities obtained, appeared to be azote. In one instance the contraction of the gas was much greater, it being reduced to nearly 1-27th of its original volume.

It now became an interesting subject of enquiry, whether the same circumstances occurred in productions found in rocks considered of igneous origin. The calcedonies from the Basaltic Rocks, near Vincenza, often contain cavities with globules of water. Some of these specimens being examined, the water was found in a slight degree impregnated with saline matter; and the azote was much more rarefied than in the rock crystal.

"It occurred to me," says Sir H. Davy," that atmospheric air might have been originally the elastic fluid included in these siliceous stones and in the crystals, and that the oxygen might have been separated from the azote by the attraction of the water, and a direct experiment seemed to confirm this idea. A chalcedony which had been bored, was placed in water free from air, under a receiver which was exhausted till a portion of gas from the interior of the crystal had escaped into a proper receptacle. This gas examined by nitrous gas was found to contain nearly as much oxygen as atmospheric air so that there is every reason to believe that the water had emitted oxygen during the exhaustion."

Sir H. Davy was anxious to find similar cases in secondary rocks: but wherever he found any such stones containing

1

cavities, they were always found to be permeable to air. He then proceeds to some speculations on the subject, which we will give in his own words:

"In reasoning upon the vacuum or rarefied state of the aëriform matter in the cavities of these rock crystals and chalcedonies, it appears difficult to account for the phenomenon, except on the supposition of their being formed at a higher temperature than that how belonging to the surface of the globe; and the most probable supposition seems to be, that the water and the silica were in chemical union, and separated from each other by cooling.

"Water in the temperature of the arctic winter is constantly a crystallized body. As a fluid, its solvent powers are increased as its heat becomes higher, and when elastic, the density of its vapour is exalted in proportion to its heat: so that an atmosphere of steam, supplied from an indefinite source above water, would render it capable of receiving a very high degree of heat. Lime retains water in combination at a heat above 250° Faht. Baryta retains it, (even under ordinary pressures) at a strong red heat, and fuses with it. It is extremely likely that a liquid hydrate of silica would exist under pressure, at high temperatures; and like all liquid bodies in the atmosphere, would probably contain small quantities of atmospheric air: and such a supposition only is necessary to account for the phenomena presented by the water in rock crystal and chalcedony." P. 373.

The author then remarks that the presence of steam in the cavity, will not allow any certain inferences from the degree of contraction observed in the liquid. And subjoins an Appendix giving an account of two specimens which differed from all the former, one containing an oily liquid; and the other a minute quantity of gas which was found to be highly compressed, instead of rarefied, as in the former in

stances.

No. 33. Some Experiments and Researches on the Saline contents of Sea Water, undertaken with a view to correct and improve its Chemical analysis. By Alexander Marcet, M.D. F.R.S. Honorary Professor of Chemistry at Geneva.

This paper, in which its lamented author has displayed all the skill and ability for which he was so justly celebrated, commences with a refutation of the opinion started by the French Chemist, Rouelle, that sea water contains mercury. Dr. Marcet's experiments seem quite decisive to shew that it does not.

The more general object of the paper was pursued in consequence of an opinion entertained by the author, and first brought forward as a conjecture in a paper on a similar sub

ject in the Phil. Trans. 1819, that the waters of the ocean would probably be found to contain traces of all substances in nature which are soluble in water. He was supplied with pure specimens of the saline matter contained in sea water by a friend who evaporated it under his own eye. The results obtained from the most careful analysis where chiefly these: No nitrates could be detected, nor any muriate of lime. Carbonate of lime was found in solution, which Dr. M. considered a new fact. He also succeeded in finding muriate of ammonia. Sulphate of soda having being supposed by some chemists to exist in sea water, Dr. M. took great pains to put the question to the test. He was convinced that this substance does not exist in sea water; and indeed considers that its occurrence would be quite incompatible with our knowledge of chemical affinities. The last circumstance investigated is the state in which potash exists in sea water, and this was found to be in a triple sulphate of magnesia and potash.

No. 34. On the ultimate Analysis of Vegetable and Animal Substances, By Andrew Ure, M.D. F.R.S.

Of this important and elaborate communication we fear we shall be unable to give our readers any account. The examination of a great number of animal and vegetable substances are given in detail, and the mode of experimenting devised by the author is minutely described, but could not be rendered intelligible without the plate which gives a view of the apparatus.

The subject of the paper last named under the chemical department naturally leads us to that of Anatomy, Physiology, and Natural History. Under this head we find several papers of considerable value: but their nature will of course preclude a very minute account of most of them.

No. 21. Some Observations on the buffy Coat of the Blood, &c. By John Davy, M.D. F.R.S.

This communication being wholly of a surgical nature, we pass it over briefly to notice the next:

No. 22. On the Mechanism of the Spine. By Henry Earle, Esq. F.R.S.

In this paper the author first describes a peculiarity which he has observed in the structure of the spine in birds, corresponding exactly to the peculiar motions which their habits require in that part different from quadrupeds. This peculiarity consists in a structure of the vertebræ, by which increased facilities for motion are given, without injury or pressure on a part of such vital importance as the spinal mar

row.

The number of cervical vertebræ in birds varies from