was ascertained that all these solutions, even those reputed as homogeneous, contain infinitely small solid particles, the presence of which is revealed, on Tyndall's method, by a beam of light. In some of them the particles—all of the same size and performing rapid oscillatory movements—are even seen under the microscope, when magnified a thousand times; while in antimonium sulphide the very formation of coarser agglomerations out of invisible particles can be followed under the microscope. In short, the authors came to the conclusion that there is no sharp limit between a state under which the mutual attractions between the particles of the solvent and the suspended particles of the dissolved body are very feeble, and a state when, these aggregations becoming of a smaller size, the forces which keep them in the solution become of a decidedly chemical nature. A new and promising method is thus given.
If we take into account the rapid accumulation of data relative to the subject of solutions and the various theories already germinating, we may hope that the day is not far off when a complete theory of these phenomena will be possible. Let us only remark that all the work hitherto done confirms more and more the idea which becomes more and more popular among chemists, and which Mendeléeff has so well expressed in a lecture delivered before the Royal Institution in May, 1889;[1] namely, that the molecules of all bodies, simple or compound, borrow their individualities from the characters of the movements which the atoms perform within the molecules. Each molecule may be considered as a system, like the systems of Saturn or Jupiter with their satellites—each separate type of such systems giving a separate type of molecules, and the chemical properties of the molecules being determined by the character of the system and its movements. It may already be foreseen that further progress in the great investigation into the mechanical basis of chemical energy will be made in this direction.
II.
One of the chief objections to the theory of evolution which was especially laid stress upon some thirty years ago, was the impossibility of producing at that time a series of "intermediate links" to connect the now existing animals and plants with their presumed ancestors from former geological epochs. To meet the objection, Darwin had to devote a special chapter in his great work to the imperfection of the geological record, and to insist both upon its fragmentary character and our imperfect knowledge of what it contains. The recent progress of both geology
- ↑ An attempt to apply to Chemistry one of the Principles of Newton's Natural Philosophy, in the Principles of Chemistry, vol. ii, Appendix I.
