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these notes, which he has there corrected in detail, giving for each mineral the correct numbers to be substituted for those printed; the fault not having been discovered till too late to correct the press. Our only object in noticing these "errors" is, that Mr. Children particularly represents his falling into them as 66 one proof among a thousand of the danger of involving plain matter of fact in unnecessary hypothetical dogmas." p. xiii.

Now we cannot help thinking that Mr. Children is somewhat too severe upon himself in calling these differences between the numbers given by Berzelius, and those which result from the common theory, errors. These differences arise from one peculiar doctrine maintained by that philosopher: namely that bodies which have weak affinities combine atom with atom, whilst in others whose affinities are more energetic, one atom of base takes two atoms of oxygen.

Now we would only ask is this doctrine of Berzelius established by experiment, or is it a mere gratuitous assumption? it certainly bears the appearance of an inference from facts; but surely before it is decidedly rejected as unworthy of admission, and leading to erroneous conclusions, it ought to be fairly refuted and shewn to be an hypothetical assumption.

In consequence however of his opinion that this doctrine of Berzelius is merely hypothetical, that his nomenclature is obscure and perplexed, and his mineralogical symbols intricate and puzzling to the student, Mr. Children has on all occasions substituted for the former, the terms commonly used in this country: and has omitted the latter altogether, substituting for them words at length. He observes in a note p. 106.

"I do not expect Berzelius will acquiesce in the change I have adopted, but as no disrespect is intended I trust he will pardon me. The English reader will I hope pardon and approve."

With respect to the system of nomenclature adopted by the author we are much disposed to agree with the translator; indeed we think great want of symmetry is to be found in all the chemical nomenclatures which have yet been brought forward, and the introduction of new names is always an evil of the first magnitude. We think also that every thing tends to induce the opinion, that in the course of time as chemical science enlarges its boundaries, the best existing nomenclature will be found deficient; and we are much inclined to consider the commonest names of substances the best, pro

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vided at the same time their chemical composition be recorded in that simple and universally applicable manner which the symbolical method affords. Mr. Children has rejected Berzelius's symbols partly because they are united with his hypothetical views. We think however that these symbols might easily have been purged from every thing theoretical, had they been thought worth retaining on other grounds; he thinks symbols however, puzzling incumbrances in themselves; and we must own we are somewhat surprized at finding him compare them with the chemical symbols adopted by the alchymists. The nature and design of the two are surely entirely different. The alchymical symbols were merely childish hieroglyphics without meaning or use, except to conceal the mysteries of the art from the eyes of the vulgar. But on the other hand when we wish to express chemical compounds in the complicated forms under which they frequently exist, and the relative proportions in which the ingredients unite, the adoption of some concise notation is not only a great saving of words, but we should suppose every student must acknowledge the great assistance afforded by such a plan, both to the conception and the memory. To a beginner it has long been our conviction that it is almost impossible to convey a clear idea of the atomic theory, for instance, without the use of some notation of this kind; and similar observations will we think apply to many other parts of the science.

The advantages in point of clearness, brevity, and assistance to the memory, derived from the use of symbolical notation, every student we think will alow are clearly exemplified in some of the admirable chemical papers of Mr. Herschell; as well as in those of other no less distinguished authors; in Dr. Henry's excellent paper on coal gas, for instance, the superiority of this mode of illustration appears to us to be most decidedly shewn. As new chemical compounds are discovered every nomenclature however ingeniously devised will be likely in some instances either to fail in affording a descriptive name, or to express it in so barbarous and complicated à manner as to be worse than useless. By algebraic symbols, on the contrary, the composition of every possible substance may be expressed with readiness, clearness, and elegance. We have perhaps said too much on this point which after all, is of minor importance. We must add however that we trust Mr. Children will excuse us if we thus venture to oppose our opinion to his, especially as he must perceive that though we may not feel quite disposed to acquiesce in one or two points of very inferior importance,

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yet upon the whole we cannot but admire the judgment and ability displayed throughout the whole undertaking. It is time however that we should proceed with our examination of the volume.

We come now to the body of the original work; it commences with a short introduction by the author, in which he points out briefly the design of his treatise, and the nature of those objects to which the blowpipe is applicable. This invaluable little instrument affords the means of readily trying a vast number of experiments for determining the nature and composition of different substances, and which though always conducted on a microscopic scale, yet present us in an instant with the most decisive results. To the mineralogist in particular it is of the most essential use; for those employed in such researches the present work is more immediately designed, and after a full description of the apparatus, and the methods of operating successfully, the author has given a detailed account of the different characteristics discoverable in each species of minerals when exposed to the action of the blowpipe.

The treatise itself commences with an historical account of the use made of this instrument. It appears to have been long known and used in the arts before it was applied to scientific purposes. It appears to have been first employed in this way by Andrew Swab, a Swedish metallurgist, about 1733. The art of using the blowpipe was transmitted tradi tionally, and little published on the subject: indeed as the author remarks, as in other practical sciences, books alone are weak masters to make adepts in this. The practical skill of Gahn in the use of this instrument was carried to greater perfection than that of any of his predecessors-as an instance, it is mentioned, that long before the question was started whether the ashes of vegetables contain copper, Berzelius had himself seen him many times extract with the blowpipe from a quarter of a sheet of burnt paper, distinct particles of metallic copper. It was from this distinguished mineralogist that the author of the present work derived his skill.

"I was so fortunate as to enjoy a familiar intercourse with this eminent man, during the last ten years of his life. He spared no pains to impart to me all that he could from his knowledge and long experience, and I have strongly felt the obligation I then contracted towards the public to perpetuate as far as in me lies the fruits of his labours."

VOL. XIX. MAY, 1823.

This it appears Berzelius did in a former work on chemistry, but this was confined to an account of the use of the instrument. The results obtained by the application of it to mineral substances, it remained for our author to describe, from his own experiments; which he was strongly urged to do by Gahn, who had promised to criticize the results "his blowpipe in his hand," had not the scheme been frustrated by his death.

Next comes a description of the blowpipe and the apparatus connected with the use of it. The author has detailed the various contrivances which have been proposed as improvements on it. The most complicated of which he rejects as absolutely useless, and considers the instrument in one of its most simple forms, as decidedly the best adapted to the purposes for which it is wanted. That of Dr. Wollaston is at once perfectly adequate to the production of the desired effects, extremely simple, and exceedingly portable. Persons unaccustomed to the instrument are apt to suppose that it requires great pulmonary exertion; this however is quite a mistaken idea: it has notwithstanding led to several attempts to substitute for the action of the lungs, bellows and other contrivances: speaking of these our author remarks,

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"By these pretended improvements, motions more or less troublesome have been substituted for a slight exertion of the muscles of the cheeks, and their inventors have demonstrated by their very contrivances, that they did not know how to use the blowpipe: they might as well have proposed to play on a wind instrument with a bladder. Our conclusion must be that all apparatus of this kind is perfectly useless." P. 18.

The notes by the translator form a very interesting and instructive appendage to the work. We will quote his remark on the same subject of contrivances to supersede the action of the lungs.

"These expedients are like the various devices for lathes and tools for gentlemen turners and carpenters, who waste their time and cut their fingers in ineffectual attempts to make a box worth sixpence, with an apparatus that cost a hundred pounds. The skilful workman needs no such aids; and the operator with the blowpipe will do well to render himself independent of them at once." Note, p. 13.

There is however one instrument of this description which, as it answers purposes to which the common blowpipe is necessarily inadequate, the translator has thought it right to

notice at some length in a note, p. 15. This is the apparatus called Brooke's or Newman's blowpipe, in which any gas or mixture of gases may be compressed with great force, and thus propelled through a jet; and in the case of a combustible mixture, the stream of gas itself being inflamed, the most intense heat is produced, so that the most refractory substances are fused in a very short time. Of this and the other apparatus plates are given in outline.

The author next discusses the point of what combustible is best. The flame of a lamp is found better adapted than that of a candle for excitation by the blowpipe: though perhaps more inconvenient in travelling.

He then treats on the art of keeping up the blast and giving a proper direction to the flame. The translator, in a note, p. 21, sums up a whole page of directions to this effect, thus: "In fewer words, the operator must breathe through his nostrils, and blow with his mouth by the mere compression of the cheeks." To produce a good heat requires some knowledge of flame and of its different parts. The author accordingly enters upon a description of flame, including the theory of the action of the blowpipe. This we consider one of the most able and interesting parts of the work; and it is greatly enriched by an abstract of Sir H. Davy's account of the nature of flame, by the translator.

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At the base of the flame of a candle, we may perceive a small part of a deep blue tint, and perfectly transparent. This forms the bottom of the flame, and terminates where the external surface begins to ascend perpendicularly. In the interior of the flame a dark part is seen through its brilliant covering. This space encloses the gases which issue from the wick, and which not yet being in contact with the air cannot undergo combustion. Round this space is the brilliant part of the flame, and a sort of thin covering may be perceived, slightly luminous, over this, thickest at the summit. It is in this outer part that the combustion of the gases is completed, and the heat the most intense. It is found that on inserting a very fine wire into a flame some remarkable appearances are observed, (for which we refer the curious reader to the work, p. 22.), which serve to indicate the relative temperature at different parts of the flame. These effects are found to be always greater just on the outside of the luminous part, and within the external part just spoken of; and they increase as we descend, keeping still in the same relative situation, till the wire comes upon the confines of the blue flame at the bottom. Here the maximum effect is produced. And it is upon this consideration that the

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