come into juxtaposition merely, thus constituting molecules. By legitimate deductions from cosmical law, the forms and structures of these molecules must always be as symmetrical as the reaction of their own constituent particles, and that of their surroundings, will allow. The law of assimilation gives the same results as mathematics in determining the forms of systems of equal, and similar, elastic and reciprocally attractive spherical forces, or centres of force, when they have settled in a state of equilibrium; proving these forms to be symmetrical in the highest degree. Here, however, Macvicar and Keely differ, in hypothesis, as to the structure of the ultimate material element; but this difference does not affect "the scaffolding" of pure philosophy, in which everything that is cognizable has its own place, is on a solid basis, is harmonious with its surroundings, and is explained and justified by them:--raising chemistry to the level and bringing it within the sphere of mechanics; investing its objects, at the same time, with all the distinctness of the objects of other branches of natural science. Because the chemist in his laboratory cannot succeed in decomposing certain substances, it has been inferred that they are essentially undecomposable, simple and untransformable; and on this hypothesis the whole science of mineralogy proceeds. But when it is considered that all of these chemical atoms, before they have come into the chemist's hands, have been securely consolidated and mineralized, so as to be able to withstand the ordeal of the volcano and the central heat, compared with which the most powerful analytic agencies of the laboratory are but a mimicry, is it for a moment to be supposed, although their internal structure were still molecular, that they would break down in the chemist's hands? Surely, all his containing vessels, which are but things of human art, must go to pieces before them.