XIII. Report on M. Alcide D'Orbigny's Memoir, entitled, General Considerations on the Geo- logy of South America. By M. ELIE DE BEAUMONT. (Concluded from Vol. XXXVI. page 62), XIV. On the Classification of Fishes. By L. Agas- XV. On the Mode of Formation of Crystalline Limestone, Contact Products, Crystalline Silicide-Slates, and Unstratified Crystalline Silicide-Rocks; with Preliminary Observa- tions on the present state of Geology, and on the Methods of Investigation pursued in that Science. By B. M. KEILHAU, Professor of Unstratified Crystalline Silicide Rocks, XVI. Analysis of Wines from Palestine, Syria, and Asia Minor. By Professor EDWARD HITCH- COCK, LL.D., of Amherst College, XVII. Description of an Improved Apparatus for Levelling Small Theodolites. By Mr JOHN SANG, Land-Surveyor, Kirkaldy. With a XVIII. Observations on the Motion of Earthquakes transmitted under the Andes. By RICHARD 111 THE EDINBURGH NEW PHILOSOPHICAL JOURNAL. On Isomeric Transmutation, and the Views recently published concerning the compound nature of Carbon, Silicon, and Nitrogen. By GEORGE WILSON, M.D., Lecturer on Chemistry, Edinburgh. Communicated by the Author.* I propose, in the following Memoir, to offer some observations on the views recently published by Dr Samuel Brown, Mr Knox, and Mr Rigg, concerning the compound nature of silicon, nitrogen, and carbon. Before entering, however, at any length on the discussion of these, I would consider, very briefly, some points connected with the general question of the simplicity and unity of matter. The great majority of chemists acknowledge the existence of some 55 simple or elementary substances. These are declared to be simple, not in virtue of any test of simplicity which the chemist has discovered and applied to them, but solely because they resist the decomposing or modifying action of all the forces which are, or at least are known to be, at man's disposal. The chemist, as it were, begins with the globe itself, and breaks it down into some thousand organic and inorganic compounds; these, in their turn, he resolves into some hundred less complex substances; and the latter, last of all, into the 55 bodies which are called simple. Here his analysis, in the meanwhile, has ended; all the forces which are at his command, for the modification of matter, having * This memoir contains nearly verbatim the substance of a lecture delivered on 6th May 1844. VOL. XXXVII. NO. LXXIII.-JULY 1844. A been spent in vain on these refractory substances. The single and combined agencies of heat, light, electricity, magnetism, mechanical pressure, and the like, have been directed in innumerable ways against them. But they have emerged from every trial, except those we are soon to consider, without betraying any sign of non-simplicity, or unfolding, if they are compound, the hidden secret of their true nature. On the negative evidence of this insusceptibility of decomposition, the residual undecomposed bodies have been termed simple or elementary: they are the visible elements out of which all things are made. It cannot be denied, however, that in the minds of many, the term "simple" has passed for something more than the expression of "hitherto undecomposed," and has been accepted as fully equivalent to essentially "indecomponible." But it would be doing injustice to the majority of chemists, to affirm that they have not employed the word "elementary" in its restricted and negative meaning, and have been willing to acknowledge the possible compositeness of all the so-called simple bodies. I refer to this the more particularly, that, in a curious volume recently published by Professor Low, exception has been taken to the maxim acknowledged among chemists, that a body should be considered simple till it can be shewn to be compound, and the opposite opinion advocated, "that a body is to be regarded as compound, when we are not able to prove it to be simple."* Mr Low is at great pains to shew, that the maxim he objects to "is unsound, and is arrived at, not by the just logic of Chemical Philosophy,' but by a chemical dogma which ought, long ere now, to have been banished from the science into which it has been introduced." Every chemist, however, will smile at this correction; for the proposition that all bodies, which cannot be resolved into something less complex than themselves, shall be accepted as simple, is quite accurate, and of much practical value, when taken in the sense in which he uses it. The simplicity of the so-called elementary bodies, is not affirmed to be intrinsic, essential, or absolute, but only to exist in relation to the decomposing or modifying forces which * An Inquiry into the Nature of the Simple Bodies of Chemistry, by David Low, F.R.S.E., &c. p. 9. t Ibid. pp. 11, 12. chemistry supplies. It remains competent to whomsoever chooses, to affirm, on the grounds of analogy, probability, direct experiment, or whatever else may seem to warrant it, that any or all of them are not simple substances: all that the chemist contends for is, that, tested by their power to resist the weapons and agents he can direct against them, they preserve their simplicity. Professor Low would have the chemical elements included among compound substances, because it violates the law of continuity in nature, to suppose some 55 bodies simple, whilst all the rest are compound. This may or may not be true; but it could do no service to term the elements compound, unless we were prepared immediately to follow up the statement, by shewing of what they are compounded. Such a proposition is consistent enough on Mr Low's part, since he offers a scheme of their composite constitution, founded on certain hypothetical views; but it is not competent to the chemist. All the knowledge he possesses of the composition of bodies, has been obtained by decomposing, or combining them, or by transforming them without decomposition, into each other. According to the characters they have shewn, when thus treated, they have been named and classified in the order of their complexity, and so as to shew, within certain limits, the nature and number of their several compo-. nents. But the elementary bodies being insusceptible of resolution into substances more simple than themselves, cannot. be affirmed to be compound in the sense the other bodies the chemist considers, are; and it is not his office to discuss their complexity on other grounds than those afforded by their behaviour, when subjected to analytic, synthetic, or purely transformative forces. Whilst, therefore, I fully sympathise with the speculative spirit that has led Mr Low to propose a scheme of elemental constitution, and differ from most of my fellow chemists, in believing that some such scheme will hereafter be realized in our laboratories, I dissent from him in thinking that the chemist has erred, in demanding that every undecomposed. body shall be considered simple. The term residual, or residuary, might indeed be better than simple, as indicating more |