RECENT SCIENCE. 817 



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 be- 

 tween a state under which the mutual attractions between the 

 particles of the solvent and the suspended particles of the dis- 

 solved 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 rela- 

 tive to the subject of solutions and the various theories already 

 germinating, we may hope that the day is not far off when a com- 

 plete 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 Mendele'eff has so well expressed in a lecture delivered 

 before the Royal Institution in May, 1889 ; * namely, that the 

 molecules of all bodies, simple or compound, borrow their indi- 

 vidualities 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 satel- 

 lites 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 in- 

 vestigation into the mechanical basis of chemical energy will be 



made in this direction. 



11. 



One of the chief objections to the theory of evolution which 

 was especially laid stress upon some thirty years ago, was the im- 

 possibility 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 knowl- 

 edge of what it contains. The recent progress of both geology 



* An attempt to apply to Chemistry one of the Principles of Newton's Natural Ph 

 losophy, in the Principles of Chemistry, vol. ii, Appendix I. 

 vol. xli. 60 



