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taken from an alloy, the metal of which is soluble in nitrie acid; but if the powder is from an alloy, the metal of which is not soluble in nitric acid, then a black residuum is left not touched by the acid; and which, when washed and carefully dried, is found, when heated, to be deflagrating; and with some of the metals, when carefully prepared, strongly explosive.

The fulminating preparation obtained from the platina alloy, when dissolved in nitromuriatic acid, gave a solution containing much platima, and very little iron. When a little of it was wrapped in foil and heated, it exploded with much force, tearing open the foil, and evolving a faint light. When dropped on the surface of heated mercury, it exploded readily at 400° of Fahrenheit, but with difficulty at 370°. When its temperature was raised slowly, it did not explode, but was decomposed quietly. When detonated in the bottom of a hot glass tube, much water and fume were given off, and the residuum collected was metallic platina with a very little iron and charcoal. We are uncertain àow far this preparation resembles the fulminating platina of Mr. Edmund Davy.

In these alloys of steel the differences of specific gravity are not great, and may probably be in part referred to the denser state of the metals from more or less hammering; at the same time it may be observed, that they are nearly in the order of the specific gravities of the respective alloying metals.

The alloys of steel with gold, tin, copper, and chromium, we have not attempted in the large way. In the laboratory, steel and gold were combined in various proportions; none of the results were so promising as the alloys already named, nor did either tin or copper, as far as we could judge, at all improve steel. With titanium we failed, owing to the imperfection of crucibles. In one instance, in which the fused button gave a fine damask surface, we were disposed to attribute the appearance to the presence of titanium; but in this we were mistaken; the fact was, we had unintentionally made wootz. The button, by analysis, gave a little silex and alumine, but not an atom of titanium ; menachanite, in a particular state of preparation, was used: this might possibly contain the earths or their basis, or they may have formed a part of the crucible. * M. Berthier, who first made the alloy of steel and chromium,* speaks very favourably of it. We have made only two experiments: 1600 grains of steel, with 16 of pure chrome, were packed into one of the best crucibles, and placed in an excellent blast furnace : the metals were fused, and kept in that state for some time. The fused button proved good and forged well: although hard, it showed no disposition to crack. The surface being brightened, and slightly acted on by dilute sulphuric acid,

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exbibited a crystalline appearance; the crystals, being elongated by forging, and the surface again polished, gave, by dilute acid, a very beautiful damask. Again, 1600 grains of steel with 48 of pure chrome were fused : this gave a button considerably harder than the former. This too was ás malleable'as pure iron; and also gave a very fine damask. Here a phenomenon rather curious was observed: the damask was removed by polishing, and restored by heat without the use of any acid. The damasked surface, now coloured by oxidation, had a very novel appearance: the beauty was heightened by heating the metal in a way to exhibit all the colours caused by oxidation, from pale-straw to blue, or from about 430° to 600° of Fahr. The blade of a sabre; or some such instrument, made from this alloy, and treated in this way, would assuredly be beautiful, whatever its other properties might be; for of the value of the chrome alloy for edge tools we are not prepared to speak, not having made trial of its cutting powers. The sabre blade, thus coloured, would amount to a proof of its being well tempered; the blue back would indicate the temper of a watch spring; while the straw colour towards the edge would announce the requisite degree of hard

It is confessed, that the operation of tempering any blade of considerable length in this way, would be attended with some difficulty.

In the account now given of the different alloys, only one triple compound is noticed; namely, steel, iridium, and osmium; but this part of the subject certainly merits further investigation, offering a wide and interesting field of research. Some attempts to form other combinations of this description proved". encouraging, but we were prevented, at the time, by various other avocations, from bestowing on them that attention and labour they seemed so well to deserve.*

It is a curious fact, that when pure iron is substituted for steel, the alloys so formed are much less subject to oxidation. Three..per cent. of iridium and osmium fused with some pure iron, gave a button, which, when forged and polished, was exposed, with many other pieces of iron, steel, and alloys, to a moist atmosphere : it was the last of all showing any rust. The colour of this compound was distinctly blue ; it had the property of becoming harder when heated to redness and quenched in a cold fluid. On observing this steel-like character, we suspected the presence of carbon none, however, was found, although carefully looked for. It is not improbable that there may

be other bodies, besides charcoal, capable of giving to iron the properties of steel; and though we cannot agree with M. Boussingault,+ when he would replace carbon in steel by silica or its

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base, we think his experiments very interesting on this point, which is worthy further examination.

We are not informed as to what extent these alloys, or any them, have been made at home, or to what uses they have been applied; their more general introduction in the manufacture of cutlery would assuredly add to the value, and consequently to the extension of that branch of trade. There are various other important uses to which the alloys of steel may advantageously be applied. If our information be correct, the alloy of silver, as well as that of platina, has been, to some considerable extent, in use at His Majesty's Mint. We do know, that several of the alloys hạve been diligently and successfully made on the Continent; very good specimens of some of them having been handed to us; and we are proud of these testimonies of the utility of our endeavours.

To succeed in making and extending the application of these new compounds, a considerable degree of faithful and diligent attention will be required on the part of the operators. The purity of the metals intended to form the compound is essential; the perfect and complete fusion of both, must in every case, be ascertained : it is further requisite, that the metals be kept for some considerable time in the state of thin fusion; after casting, the forging is with equal care to be attended to; the metal must on no account be overheated; and this is more particularly to be attended to when the alloying metal is fusible at a low temperature, as silver. The same care is to be observed in hardening: the article is to be brought to a cherry-red colour, and then instantly quenched in the cold Huid.

In temperiug, which is best performed in a metallic bath properly constructed, the bath will require to be heated for the respective alloys, from about 70° to 100° of Fahrenheit above the point of temperature required for the best cast steel. We would further recommend, that this act of tempering be performed twice; that is, at the usual time before grinding, and again just before the last polish is given to the blade. This second tempering may, perhaps, appear superfluous; but upon trial its utility will be readily admitted. We were led to adopt the

practice by analogy, when considering the process of making and tempering watch springs.

New Series, vol. V.

tanab in dist lte FETC

idina cellula

Memoir illustrative of a general Geological Map of the principal

Mountain Chains of Europe. By the Rev. W. D. Conybeare,
FRS. &c.

(Continued from p. 149.)

GREAT SALIFEROUS SERIES, Including, a. The rothetodteliegende.

b. The alpine or magnesian limestone,

c. The variegated or new red sandstone. In comparing the series of deposits which immediately succeed the great carboniferous order as presented in England, and in some parts of the Continent, we shall

, perhaps, perceive rather a parallelism than identity of formations in the representatives of rothetodteliegende and the alpine limestone; but in the variegated sandstone an unequivocal identity is manifested.

4. Rothetodteliegende.-Conglomerates, including rolled fragments of the neighbouring rocks, characterise this formation: the cement is sometimes argillaceous, sometimes quartzose; by the diminution in size of the fragments, the rock often passes into a sandstone more or less granular. Beds of red micaceous shale alternate in the formation; it contains subordinately in some places carboniferous beds (distinct, however, according to Freisleben, from those of the true coal formation). Trap rocks (amygdaloid and porphyry) are often associated with these deposits, usually, as it should appear, in their lowest members where they rest on the true coal series. Beds of limestone also occur, though sparingly. The upper members where they support the alpine limestone, pass into a calcareous conglomérate called in the Hartz and neighbouring districts, the Weissliegende. This is by some authors considered as a distinct formation; by others (with whom I am inclined to agree), it is included as the last deposit of the rotheliegende. Ores of iron, cobalt, and copper occasionally occur.

The pétrifactions of this rock appear to belong chiefly, if not exclusively, to the vegetable kingdom.

All circumstances indicate a near connection, but not an identity, of formation between the rothetodte and the great carboniferous series. * It seems rather to hold an intermediate place

between this and the following deposits, and to introduce, as it Were, the latter.

b. The Alpine Limestone; Zechstein, or Magnesian Limestone. (Werner's first Floetz Limestone.)-This formation is very variable in different places, and may be said generally to present in distant districts a parallelism rather than identity of deposits. The prevailing rock in the continental deposits (zechstein) is a grey compact, and generally argillaceous limestone; sometimes slightly granular, and having a small degree of lustre from the facettes of the calcareous crystals imbedded: its colour is grey or bluish, sometimes acquiring a reddish tinge; it contains subordinate beds of magnesían limestone, of ferriferous limestone, of cellular and crystalline limestone (rauchwacke), of fetid limestone, and of bituminous and cupriferous' marl slate. Copper, galena, calamine, and mercury, are among the metallic products of this formation ; and the association of rock salt and gypsum attest its connexion with the superimposed sandstones which also abound in these minerals.

Organic remains are scarce in this formation, speaking generally, but yet in particular spots and beds occur even abundantly: the following species are enumerated by Sclottheim; but I am tot at present able to identify all the names employed with the synonymes in English writers.

Gryphites aculeatus,
G. gigas,
G. arcuatus,
Pecten textorius,
Pecten salinąrius,
Mytilus rostratus,
Terebratula alata,
Terebratula lacunosa,