gas are equally clear. When equal volumes of oxymuriatic gas and hydrogen are inflamed together, this gas alone is formed; there is no deposition of water, and no water can be procured from it, excepting when compounds are used known to contain water or oxygen. Sir H. Davy does not assert that oxymuriatic gas may not contain oxygen; he merely maintains that it has not yet been decompounded, and that till it has been decompounded, it must be considered as a simple substance. The name oxy muriatic is evidently not very consistent with its simple nature, and he has accordingly discarded it and substituted chlorine, which expresses a physical quality of the gas. The same necessity of change extending to all substances containing chlorine, a total reform in this part of nomenclature became absolutely necessary; and we are happy to say has been effected on the most philosophical principles. The new names proposed by Sir H. Davy for this class of bodies are independent of theory, and will not require change, whatever discoveries may be hereafter made relative to their composition, which is a great advantage in a progressive science like chymistry. A superficial observer might perhaps complain, that as these names convey no information respecting the constituent parts of substances, they are of no assistance to the student, and a great burden to the memory. But such an objection, were it correct, is of little importance; their advantage is, that they convey accurate ideas, and cannot retard the progress of discovery. The object of science being truth, that nomenclature is best which most promotes its acquisition.

Sir H. Davy considers chlorine and oxygen analogous to each other, and to be similar acidifying principles; he has accordingly placed them together in his Elements in one class, in opposition to all other substances. Chlorine, like oxygen, is attracted by the positive pole of the Voltaic battery, and repelled by the negative. Both form acids by union with certain inflammable substances. The metallic combinations of both are also allied in many properties: and there are triple combinations of chlorine with carbon and hydrogen, very similar to certain vegetable substances, of which carbon, hydrogen, and oxygen are the constituent parts.

This doctrine respecting chlorine appears to us one of the most perfect parts of the whole theory of chymistry. Satisfied with embracing the known, it does not extend to the unknown; nothing in it is taken for granted, and nothing imagined; it rests wholly upon sound logic and true philosophy. The fate of all new doctrines is opposition, and this doctrine is not an exception. The very few who are dissatisfied with it, defend

the old hypothesis, as the phlogistians did their expiring creed. Since they are obliged to acknowledge that muriatic acid gas is not a simple substance, they call it a compound of an unknown basis and water; and since they will not grant oxymuriatic gas to be a simple substance, they call it a compound of the same unknown basis and oxygen; and this unknown basis, say they, is muriatic acid. Assertions and imaginations of such a description might, among the alchymists, very well pass for sound arguments and realities, but in the present state of the science, they are unworthy of serious consideration.

One of the most interesting parts of Sir H. Davy's work is that on "chymical attraction, and the laws of combination and decomposition." In this chapter he developes the doctrine that bodies combine only in certain definite proportions, and controverts the opinion that they are capable of uniting in all quantities. His arguments are facts, which are alone deserving of confidence in an experimental science. By an appeal to facts, the accuracy of which cannot be doubted, he has satisfactorily shown that a substance either combines with one quantity of another, or with a double, triple, or quadruple quantity of it, or to express it more concisely, with some multiple or divisor of that quantity. Thus there are four distinct combinations of oxygen and nitrogen, viz. nitrous oxide, nitrous gas, nitrous acid gas, and pale nitric acid: the first is composed of one quantity or propor. tion of nitrogen and one proportion of oxygen, the weights of which are to each other as 26 to 15; the second consists of one proportion of nitrogen, the number of which is 26, and two proportions of oxygen, which are equivalent to 30, or twice 15; the third contains four proportions of oxygen to one of nitrogen, and the fourth five to one. He has also proved that the relation of the proportions, or of the saturating powers of substance, is constant and regular, so that their states being ascertained, in respect to neutrality, or the excess of one ingredient or the other, the composition of bodies may be calculated on a few data, and chymistry be reduced almost to a mathematical science. Thus, oxygen combines with twice its volume of hydrogen, and twice its volume of chlorine, to form water and euchlorine; and two volumes of hydrogen require two volumes of chlorine, to form muriatic acid gas. Thus, there are two combinations of phosphorus and chlorine, the one a liquid, and the other a solid body, and both decompose and are decomposed by water; the hydrogen of which, uniting with the chlorine, forms muriatic acid gas, and the oxygen uniting with the phos

phorus, in one instance, forms phosphorous acid, and in the other phosphoric ;-or in other words, the phosphorus which. was combined with two proportions of chlorine, can only acquire, by the decomposition of water, two proportions of oxygen, and that which in the solid substance was united with three proportions of chlorine, cannot, by the decomposition of water, acquire less than three proportions of oxygen.

We shall give another example, and from Sir H. Davy's work. "There is not," says he, "perhaps in the whole series of chymical phenomena, a more beautiful illustration of the theory of definite proportions than that which is offered in the decomposition of hydrophosphorous acid (which consists of four proportions of phosphorous acid and two of water.) Four proportions of the acid contains four proportions of phosphorus, and four of oxygen; two proportions of water contain four proportions of hydrogen, and two of oxygen. The six proportions of oxygen unite to three proportions of phosphorus to form three of phosphoric acid, and the four proportions of hydrogen combine with one of phosphorus to form one proportion of hydrophosphoric gas, and there are no other products. This relation of proportions might be illustrated in a thousand ways, particularly by the decomposition of metallic salts by metals, and of earthy salts by alkalies;-in the former, when the salts are neutral, there is merely an exchange of metals, the one taking the place of the other, without any exchange whatever in the combined proportions of oxygen and acid: so that M. Gay Lussac's law, respecting these neutral metallic salts, is perfectly correct, -that the acid is proportionable to the oxygen, and that the one being known, the quantity of the other may be calculated. This doctrine, in its present extended form, is of very recent origin. When chymistry began to be cultivated as a science, all those who investigated the subject of affinities, seemed satisfied that bodies were capable of combining only in certain determinate proportions, but their views were not at all definite, and apparently rather the result of general speculations on the nature of attraction, than induction from facts. Mr. Higgins was the first who descended to particulars, and embracing the corpuscular philosophy, attempted to prove that bodies combine particle to particle, and, of course, in definite quantities. Thus, he considered water a binary compound of one particle of hydrogen and one of oxygen, and sulphureous acid gas as a similar compound of one of sulphur and one of oxygen, whilst he supposed sulphuric acid to be a ternary compound of one particle of sulphur and two of oxygen. But Mr. Higgins's views were VOL. I. New Series.

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very much neglected till the attention of the learned were directed to them by Sir H. Davy; and Mr. Dalton had all the merit of being the original founder of this doctrine. Mr. Dalton is certainly deserving of great praise for what he has done. He revived the theory when it was entirely forgotten, and supported it with much ability; extending its empire, . and showing its agreement with a great number of facts. Of all the authors who have written on it, Sir H. Davy, in the present work, has taken the most comprehensive view of the subject, and introduced, by means of his original researches, the greatest harmony into all its parts. And he, too, has the merit of separating it from the corpuscular philosophy, and of making facts its only foundation. Mr. Dalton, on the contrary, appears to be a fond disciple of Leucippus and Democritus, who, above 2,000 years ago, taught that all things were composed of immutable atoms. This philosopher not only believes in the existence of atoms, but even imagines. himself acquainted with their invisible forms, and conceives himself capable of calculating their relative weights and their number in any given volume of elastic fluid. Admitting his premises, his conclusions we will allow are capable of demonstration; but the existence of atoms, and even of matter itself, must be taken for granted, and does not admit of rigorous proof. We, therefore, consider the science as much indebted to Sir H. Davy for having devested this important theory entirely of its hypothetical dress, and placed it before the eyes of his readers in its proper attitude.

Nothing can show to greater advantage the benefits of the theory of definite proportions than the work before us. Everywhere there is the greatest precision; the compositions of bodies are rigorously ascertained and compared together; no ingredient is overlooked as insignificant; water in particular, hitherto so much neglected, has received a due attention, as forming a part of the character of the compound. The proportions of the constituent parts of bodies are represented by numbers, and the memory is but little burdened with retaining them, as each simple substance has always the same numerical representative. Thus 15 is the general symbol of oxygen, and 26 of nitrogen, so that when the proportions are known in which they combine together, the weights of the constituent parts are most readily found.

The late progress of this theory has been surprisingly rapid. It now embraces all the substances we are accurately acquainted with. The numbers representing oxygen and chlorine, hydrogen, sulphur, phosphorus, and carbon, and most of the metals, have been determined, and the proportions

in which all these substances combine respectively with each other, is in a great measure ascertained. So that chymistry is now become almost a numerical science, and its operations admit of being reduced to numerical exactness.

The refutation which the author has given of Berthollet's doctrines appears to us to be completely satisfactory. He has repeated some of his experiments, and found them incorrect; others he has explained on more simple principles; and Paff has proved, in some of the particular instances adduced by the French chymist himself, that quantity or mass has no influence in modifying the results, or of enabling weak to overcome powerful attractions. We must confess that this refutation affords us no little pleasure, as Berthollet's views had not the simplicity of truth to recommend them, and their tendency was to create confusion, and to render chymistry an art rather than a science." If chymical attraction," observes Sir H. Davy, "be regarded as capricious in its effects, and as tending constantly to produce different arrangements, chymistry is left without a guide, without any certain combinations, and no results of analysis can be perfectly alike: but fortunately for the progress of science, this is not the case: the changes of the terrestrial cycle of events, like the arrangement of the heavens, and the system of the planetary motions, are characterized by uniformity and simplicity; weight and measure can be applied to them, their order perceived, and their laws discovered."

We cannot, in conclusion, deny ourselves the satisfaction of transcribing the following extract, as a specimen of the ruling impressions which the ardent and successful pursuit of science has left upon the mind of Sir Humphry Davy. "It is contrary to the usual order of things, that events so harmonious as those of the system of the earth, should depend upon such diversified agents as are supposed to exist in our artificial arrangements; and there is reason to anticipate a great reduction in the number of the undecompounded bodies, and to expect that the analogies of nature will be found conformable to the refined operations of art. The more the phenomena of the universe are studied, the more distinct their connexion appears, the more simple their causes, the more magnificent their design, and the more wonderful the wisdom and power of their AUTHOR."

We have little doubt that these solemn views of the grandeur and simplicity of the works of God have been useful to Sir H. Davy in the regulation of his scientific pursuits, and have given a zest to every object. Nor can we withhold from him the tribute of our thanks, for his virtuous, and, we