63. It requires a very extensive survey of the actual dominion of science, and a great sagacity to judge, even in the loosest manner, what is beyond the possible limits of human knowledge. Certainly, since the time when this passage was written by Playfair, more steps have been made towards realising the sanguine anticipations of Bacon than in the two centuries that had elapsed since the publication of the Novum Organum. We do not yet _know_ the real nature of heat, but few would pronounce it impossible or even unlikely that we may know it, in the same sense that we know other physical realities not immediately perceptible, before many years shall have expired. The atomic theory of Dalton, the laws of crystalline substances discovered by Häuy, the development of others still subtler by Mitscherlich, instead of exhibiting, as the older philosophy had done, the idola rerum, the sensible appearances of concrete substance, radiations from the internal glory, admit us, as it were, to stand within the vestibule of nature’s temple, and to gaze on the very curtain of the shrine. If indeed we could know the internal structure of one primary atom, and could tell, not of course by immediate testimony of sense, but by legitimate inference from it, through what constant laws its component molecules, the atoms of atoms, attract, retain, and repel each other, we should have before our mental vision not only the Latens Schematismus, the real configuration of substances, but their _form_, or efficient nature, and could give as perfect a definition of any one of them, of gold for example, as we can of a cone or parallelogram. The recent discoveries of animal and vegetable development, and especially the happy application of the microscope to observing chemical and organic changes in their actual course, are equally remarkable advances towards a knowledge of the Latens processus ad formam, the corpuscular motions by which all change must be accomplished, and are in fact a great deal more than Bacon himself would have deemed possible.[207] [207] By the Latens processus, he meant only what is the natural operation by which one form or condition of being is induced upon another. Thus, when the surface of iron becomes rusty, or when water is converted into steam some change has taken place, a _latent_ _progress_ from one form to another. This, in numberless cases, we can now answer, at least to a very great extent, by the science of chemistry. |But should be kept within bounds.|