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tily concur with the translator in the very just encomiams he has bestowed upon his author.

“ We feel," with him “perfectly confident, that no apology for presenting this translation to the public, nor any eulogy on the author of the original work, are at all necessary.

The name of Berzelius, as a skilful and patient experimenter, stands almost unrivalled ; and the present Essay amply' vindicates his claim to the high reputation he has acquired. It is an invaluable collection of important and new facts, and admirably supplies the want, which has long been felt and acknowledged, of a scientific practical treatise on the blowpipe.”

The translator next proceeds to apologise to his author for some liberties which he has taken with the work. Many of these, he says, consist merely in the omission of details which appeared to him unnecessary; but the most important are those which affect the peculiar chemical theory and symbols which Berzelius bas adopted. Mr. Children has thought it advisable, wherever any expressions occur in the work founded on these principles, or wherever any of the symbols are employed, to substitute for them more common expressions not involving the peculiar hypothesis of his author, and to translate the algebraical symbols into words at full length. The discussion of these points occupies the principal part of the prefatory division of the work. A general explanation is next given of the leading principles of Berzelius's system of mineralogy. His arrangement is purely chemical ; at the same time, the external forms and characters of the substances are employed as important secondary distinctions, although the chemical composition is the fundamental principle of arrangement. The chemical principle upon which the whole depends, is,

“ That the elements, of which minerals are composed, unite with forces proportionate to the differences that exist in their mutual electrical relations. Hence one or more electro-positive, and one or more electro-negative ingredients, must be found in every compound body: thus, if it be formed of oxides, for every ingredient which we call a base, another must act as an acid, although the latter, in its insulated state, may not have the sour taste and other properties by which acids, usually so called, are distinguished: such are silica and the oxides of titanium, columbium, and many other metallic oxides, so that all the immense series of earthy mi. nerals may be classed after the same principles as salts. An ingredient which acts as an acid in one case, may act as a base in another, according as it is electro-negative, or electro-positive, with respect to the substance it combines with : and consequently in a combination of two acids, the weaker may serve as a base to the stronger.

The order of arrangement depends on the electrochemical properties of the elements of which mineral substances are composed, proceeding from the most electro-negative oxygen, to the most electro-positive potassium : but as we are yet only very imperfectly acquainted with the electro-chemical relations of the simple bodies, we must be contented with an approximate arrangement.” P. xxiii.

Having thus just given the fundamental principle upon which Berzelius proceeds in his system, we will not enter into the details of it, but content ourselves with recommending them strongly to the attention of our readers, as given in the subsequent pages of the work.

Before we proceed, however, it may be desirable to many of our readers to have a short sketch of the principle apon which the atomic theory proceeds; as that theory and certain deductions from it form the subjects of some discussion in the work before us.

The doctrine of definite proportions or the atomic theory, is decidedly the most important extension which chemical science has received of late years. The establishment of these doctrines has done much towards imparting a mathematical precision to our views of chemical composition. It was observed, that, when one substance forms with another several different compounds, according to the different proportions of that second body, with which it unites, then, the numbers which express those proportions of the second body by weight, are always multiples by'a whole number of the first of them; and if these be reduced to their lowest terms, and the weight of the first body be expressed by a number proportionally reduced, this number for the first body, and unity for the other, give what are called the atomic weights of the two bodies. And it was further observed, that the number being thus determined for the first body, if that body became, in its turn, united to another in several proportions, the weights of it in each of those proportions, are exact multiples of that precise number which was in the former case taken as its atomic weight. In this way every substance in chemistry has a particular number affixed to it; and we owe to Mr. Dalton the ingenious idea that these numbers represent the weights of an atom of each body; for as there cannot be a combination of atoms, except in numbers which are whole multiples of each other, (a fraction of an atom being an absurdity) and as chemical combinations must be formed by unions among the ultimate atoms of bodies, so we can only account for the differences of the numbers above

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mentioned, by supposing the atoms of different bodies to be of different weights. This beautiful theory, which has opened to us a vast variety of new ideas respecting the phenomena of nature, has been ably and successfully studied and improved by many of the most eminent chemists of the age. In our own country no man has done more for it than Ďr. Thomson ; and in foreign countries Berzelius stands foremost on the list of those chemists who have directed their labours to the extension and improvement of the atomic theory. He has made many important observations, some of which are collected in certain general rules known by the name of Berzelius's canons. One of these Mr. Children has alluded to as more closely connected with the mineralogical system and symbols of his author, it is this:

When two elements combine, one of them is always supposed to be electro-positive, and one electro-negative with respect to the other. And compound atoms of the first order (that is, composed of only two simple elementary atoms) having a common electro negative element, always combine in such proportions that the number of atoms of the electro-negative element of one, is a multipłe by a whole number of that same number in the other.”

Mr. Children regards this canon as differing in nothing essential from the common doctrine of chemical proportions, and that in fact it is merely an hypothetical extension of it. With the greatest deference to the high chemical abilities and fame of Mr. C. we cannot help remarking that we think his observations on this point somewhat unfounded. The canon of Berzelius is an extension of the atomic theory, but surely not an hypothetical one; at least it is not more hypothetical than the whole of that theory itself is. It surely cannot be considered as differing in nothing essential from the common theory; it expresses what its author at least believes to be a general fact. If that fact is not true, or not general, let it be shewn that such is the case, and the canon falls to the ground.

It appears that in a subsequent part of the work, the author had given the atomic composition of each mineral which he describes, expressed in the symbolical notation which he adopts, and the atomic numbers assumed in compliance with another part of his theory. The translator has given the substance of these statements in words at length, in a continued series of notes to that part of the work in which they

It appears from “a note to the reader” following the preface that he considers himself guilty of some "errors” in

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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 “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 pbilosopher: 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 oxygep.

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 bas 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 assist. ance 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 a 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 thos venture to oppose our opinion to his, especially as he most perceive that though we may not feel quite disposed to acquiesce in one or two points of very inferior importance,

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