Imatges de pàgina

generation is a true crystallization. The question then is reduced to this problem :-can the liquors capable of forming an organised being by crystallization be prepared only by other organised beings. This is the most common process of nature at this time, though, at the first beginning, she may have followed a different plan. It is then demonstrated that she may still employ it, and observation can only decide, whether the has entirely renounced it.'

The inconclusiveness of the above reasoning is too obvious to require refutation. It is only necessary to remark, that spontaneous generation, in our author's language, is very different from the same system of the earlier English philosophers, who possessed equal ability, judgment, and piety. They supposed that the Almighty had originally created matter with diftinct properties, capable, in given situations, of producing beings without his immediate interposition; nor was it, in their opinion, at all derogatory from his honour to suppose him capable of forming a vast system, where each distinct part had a power of repairing its own defects, or its gradual decay. It is obvious, that the system of M. de la Metherie is very different,

If we were to examine some other part of this author's theory, we should find it equally defective: in that passage, particularly of his theory of the earth, for instance, where he contends, that metallic veins are coeval with the rocks in which they are contained, because if a cavity had been originally left, the weight above would have crushed the superincumbent part. A little reflection would have shown him, that it is not necessary a hollow should have been originally in that spot, and that the resistance from the cohesion or the arched form might have been sufficient to have preserved it. We know that there are vast cavities in the earth, whose roofs are supported by these means.

A curious phænomenon in the natural history of the earth, which has occafioned much discussion, and continues still the subject of enquiry, is the regularly formed basaltes. It was almost decided that it was a rock melted and crystallized ini this peculiar form, when two German chemists, M. M. Werner and Wedenman, discovered a mass of basaltes resting on coal *. This the editor of the Journal de Physique explains,

• In another memoir of M. Werner, which we have seen since writing the above, he meotions an argument of somewhat more force, viz. his having obterved a balaltic rock resting on clay, land, and wache. From this allo he concludes, that tasaites are the production of water. But it is well known that a part of the basaltic mountain in the north of Ireland refts on a calcareous ftratum, and this proves only that basaltes is a production, posterior to the formation ci ftrata in consequence of depofition from water.


by supposing that water is essential to the formation of basaltes, and consequently the cooling may have been too sudden to admit of the destruction of the coal. This answer we cannot admit, for a regular crystallisation is in every instance inconfiftent with rapid cooling. It is more probable, allowing the fact, which is not, however, very clearly stated, or unexceptionably supported, that lava falling in a melted state on a bed of coal, and immediately excluding the air, would affect the coal only to a certain distance, whose ashes would combine with the lower lamina of the melted mass. Or it may have happened, that the coal was formed subsequent to the basaltes, as baron Born found veins of coal in the retractions of a common lava.

· M. Dolomieu has considered this subject in general, instead of answering the German mineralogists more particularly, and his memoir deserves attention, as it contains some very important observations on basaltes. It is introduced by a description of what has been called the Egyptian basaltes, a stone very hard, black, and greatly prized for its durable nature, and the high polish of which it was capable. It was the subItance of many ancient works in ftatuary, and was brought fiom Ethiopia: it is styled by Strabo and Herodotus lapis Ethiopicus, and it is said to equal iron in hardness. Many works in this stone remain, which M. Dolomieu, after a care, ful examination, thinks are not volcanic, with the exception of a single statue of the Villa-Borghese, covered with hieroglyphics, and formed of a black lava pierced with numerous little pores. The other black stones belong to the trapps, the fchoris in mass, rarely finely grained, but often of a scaly texture, like the hornblend.

The most frequent of these black stones are granites, in which the black scaly schorl predominates so much as to give them their particular colour, while the white spar is united so sparingly, and in such minute threads, with the rest of the mass, or in such transparent particles, as to be almost invísble. In reality, he adds, the black compact lavas resemble so clofely the trapps, and the natural horn-itones, as to be indistinguitra able by external characters, and even by analysis: a careful and scientific examination of the surrounding country is often alone able to determine the difference; "for lavas often preserve the grain, colour, texture, and other external characters of the rocks from which they are formed,' without any addidition or diminution; resembling rather the fusion of metals than any other efect of fire. It was our author's opinion in his former work, his Description of the Pontiæ Insulæ, that basaltes was the effects of the lava being cooled by water, or as he paradoxically expresses himself, the regular retraction of


the prisms is the effect of the sudden cooling. The trapp, or the schorl in mass, is not, he thinks, the only earth which in cooling assumes this form, as every kind of lava is occasionally crystallised in the same way; and earth crystallising from a watery folution, as the volcanic tufa of the Campagnia of Rome, will occasionally assume the prismatic form. On the whole, he concludes, that basaltes is a vague indeterminate term, leading to no certain conclufion; that the appellations should be prismatic and globular lavas, while the regularity of form, though most commonly depending on a cryftallzation, in consequence of fusion, may sometimes happen when the fluidity is occafioned by solution, and in neither instance is the form connected with stones of a peculiar nature.

Such are M. Dolomieu's ideas; and as he has attended closely to the effects of fire in volcanic countries, his observations deserve much attention. Long before the publication of his work on the Insulae Pontiæ, we suggested the suspicion, that the fimilarity of the trapps to the basaltes arose from the fusion taking place in the bowels of the earth, and the little change that could in such a situation take place in the ingredients. But that the regular crystallization can be owing to the rapid cooling, is repugnant to every other chemical fact, and it is repugnant to observation, which shows that basaltic columns are often found where water could not probably have been at the period of their formation. In short, though the different facts recorded add to our knowledge of nature, and the changes that have taken place on the globe, they scarcely improve the philosophy of this branch of natural history.

There is one part of this subject which, if well founded, will materially influence the systems of cosmogony; and it is a fact which we have formerly alluded to, viz. the reduction of some of the earths to a metallic state, which were supposed not to have the slightest connection with metals. We sometime ago mentioned that the calcareous earth, magnefia, and the earth of alum, had been apparently reduced, and we added soon afterwards, that the experiment was found to be fallacious. In fact, M. Klaproth asserted, that the pretended reguli were only siderite, formed by phosphoric acid in the charcoal, joining with some ürn on the Hessian crucible. He challenged the authors M.M. Tondi and Riprecht to the trial: they accepted the challenge; no earth was added, and no regulus was produced. M. Klaproth was seemingly defeated. Since that time, chemists have been divided in opinion, but the best appeared to lean to the system of M. M. Tondi and Ruprecht. In this situation we shall give the result of experiments made to a greater extent, and with a more exact attention. From a view of these,


there will be little necessity of our deciding either in favour of, or zgainit their authenticity.

The author of the memoir, whose steps we shall follow in this account, is M. Tihausky, first lieutenant of the imperial founderies, who introduces his observations by remarking, that the apparent utility of this discovery, and the natural desire of extending his knowledge, led him to repeat M. Tondi's experiments: that chemist had !imself repeated the experiments before M. Tihauíky, in the public laboratory at Vienna. The fiift objects of our present author's rese:rches were the tungStein and molybdlæna: but on these subjects he has added no. thing sew. Our principal attention must be directed to the pretended reduction of the simple earths.

The calcareous earth was put into a H ian crucible, after being formed into a parte with linfeed oil and charcoal, covered with bones well calcined and washed, to prevent the access of air. The fire was raised tothe greatest height, and continued above half an hour. The metal obtained, in colour and brilliancy resembled platina. Its texture was granulated, and when broken appeared like steel. The line which it formed on thie touchitone refembled, in its grey whiteness, that made by platina. It was brittle, susceptible of a beautiful polish, and magnetic only, when broken down to a powder. Four grains and a half of metal were produced from 100 of pure earth, and its specific gravity was 6.571. M. Tondi called it pardeniuni.

The metal obtained from magnesia, treated in the same manner, was of a cinereous colour, refembling martial platina : it. in other refpects resembled the parthenium: from 100 grains cf earth 3 of metal were only procured, of a specific gravity. equal to 7.380. This M. Tondi called austrum.

From the barytic earth in a very pure state, treated in the same way, a metal very similar to the austrum was procured. From 100 grains of earth 4 grains of a metal of a specific gravity equal to 6.744 was produced, which was styled borbonium.

The metal obtained from earth of alum resembled steel in colour, with reddish spots. Its texture was also granulated, and it broke with the greyish colour of steel. In other respects it resembled the former metals, affording 7 grains from 100 of the earth, of the specific gravity of 6.184.

From these facts it will appear, that the new metals greatly re'emble each other, which leads us to think that they are produced from one common substance. It is remarkable also, that no metal is produced if all communication of air is taken away; and in a larger crucible or a less viclent fire, those portions of carth contiguous to the crucible are only reduced. Besides, all the metal procurce, not magnetic, was in so minute a quantity, and with such different appearances, as plainly to indicate some other source; and in the scoriæ glass was almost always found, resembling that which is, in other operations, procured from the same earths. To this it may be added, that, as in all thele experiments the metal in the crucible, at least on its internal substance, must be reduced, the metal found in these processes should, in every instance, be a mixed one. This led our author to a series of experiments, in which he discovered that the crucible alone afforded iron; but when the process was conducted with powdered bone, the metal was only magnetic in its divided state. The results then in these different experiments was truly siderite : the appearances which we have mentioned support this resemblance, and the chemical qualities which, to shorten our account we have not noticed, are those of fiderite only. The earth of borax, also, which was reduced in M. Tondi's experiments, resembled these metals which we have described; and as calcined bones were essential to the success of the process, we must suppose the fource was the same.

There has been a more recent discovery in Cornwall of an earth apparently metallic, of which we can only give an imperfect account from a foreign Journal. It is with regret that we perceive no work in this kingdom which conveys an early account of such discoveries, or that our offer of consigning a few pages of this Journal for the purpose has been overlooked. Mr. W. Gregor is said to have found an earth at Menackanite in Cornwall, resembling gunpowder. It dissolves in the vitriolic acid, and the solution is yellow. If bright iron is added it assumes a reddish colour resembling amethysts. Phlogisticated alkali added to this martial amethystine solution precipitates a yellow white powder; and tincture of galls gives the same solution an orange colour. If the nitrous acid is added to the amethistine solution, and to the solution changed by the galls, the first assumes a blue colour, and the second a black. Mangunele produces nearly the sanie effects on these two liquors.

(To be continued occasionally.)


DIVINITY, RELIGIOUS, &c. The Meaning which the Word Mystery bears in the New Testament,

confidered and applied, in a Sermon preached to an Assembly of Mi| nifiers. By J. Toulmin, M. A. 8.00. 15. Johnson. 1791. IT is Mr. Toulmin's object to show, that, in the New Testa

ment, what has been concealed, and is afterwards explained, is usually called a mystery, and his chief conclufion is, that no


« AnteriorContinua »