506 Dr. D. MendeUeff [May 31 



WEEKLY EVENING MEETING, 



Friday, May 31, 1889. 



Sir Fbederick Abel, C.B. D.C.L. F.R.S. Yice-Presklent, 

 in the Chair. 



D. Mexdeleeff, Esq. LL.D. 



PROFESSOR OF CHEMI.STKT IX THE UXnERSITT OF ST. PETERSBURG. 



An Attempt to apply to Chemistry one of the Frinciples of Newton 8 

 Natural Philosopliy . 



Nature, inert to the eyes of the ancients, has been revealed to us as 

 full of life and activity. The conviction that motion pervaded all 

 things, which was first realised with respect to the stellar universe, 

 has now extended to the unseen world of atoms. No sooner had the 

 human understanding denied to the earth a fixed position and 

 launched it along its path in space, than it was sought to fix immov- 

 ably the sun and the stars. But astronomy has demonstrated that 

 the sun moves with unswerving regularity through the stur-set 

 universe at the rate of about 50 kilometres j^er second. Among the 

 so-called fixed stars are now discerned manifold changes and various 

 orders of movemeut. Light, heat, electricity — like sound — have been 

 proved to be modes of motion ; to the realisation of this fact modern 

 science is indebted for powers which have been used with such 

 brilliant success, and which have been expounded so clearly at this 

 lecture table by Faraday and by his successors. As in the imagination 

 of Dante, the invisible air became peopled with spiritual beings, so 

 before the eyes of earnest investigators, and especially before those of 

 Clerk Maxwell, the invisible mass of gases became peopled with 

 particles : their rapid movements, their collisions, and impacts became 

 so manifest that it seemed almost possible to count the impacts and 

 determine many of the peculiarities or laws of their collisions. The 

 fact of the existence of these invisible motions may at once be made 

 apparent by demonstrating the difi'erence in the rate of diffusion 

 through porous bodies of the light and rapidly moving atoms of 

 hydrogen and the heavier and more sluggish particles of air. Within 

 the masses of liquid and of solid bodies we have been forced to 

 acknowledge the existence of persistent though limited motion of their 

 ultimate particles, for otherwise it would be impossible to explain, for 

 example, the celebrated experiments of Graham on diffusion through 

 liquid and colloidal substances. If there were, in our times, no belief 

 in the molecular motion in solid bodies, could the famous Spring have 

 hoped to attain any result by mixing carefully dried powders of 

 potash, saltpetre, and acetate of soda, in order to produce, by pressure, 

 a chemical reaction between these substances through the interchange 



