EVOLUTION AND MUTABILITY OF -MATTER/ 271 



diffusion. The microscopic observation of alloys by 

 H. and A. Lechatelier, J. Hopkinson, Osmond, Charpy, 

 J. R. Benoit; researches into their physical and 

 chemical properties by Calvert, Matthiessen, Riche, 

 Roberts Austen, Lodge, Laurie, and C E. Guillaume; 

 experiments on the electrolysis of glass, and the 

 curious results of Bose upon electrical contact of 

 metals, show in a striking manner the chemical and 

 kinetic evolutions which occur in the interior of 

 bodies. 



Migration under the Action of Weight. — An ex- 

 periment by Obermeyer, dating from 1877, furnishes 

 a good example of the motions of solid bodies 

 through a hardened viscid mass, taking place under 

 the influence of weight. The black wax that 

 shoemakers and boatbuilders use, is a kind of resin 

 extracted from the pine and other resinous trees, 

 melted in water, and separated from the more fluid 

 part which rises from it. Its colour is due to the 

 lampblack produced by the combustion of straw and 

 fragments of bark. At an ordinary temperature it is 

 a mass so hard that it cannot always be easily 

 scratched by the finger-nail; but if it is left to itself 

 in a receptacle, it finally yields, spreads out as if it 

 were a liquid, and conforms to the shape of the vessel. 

 Suppose we place within a cavity hollowed out of a 

 piece of wood a portion of this substance, and keep it 

 there by means of a few pebbles, having previously 

 placed at the bottom of the cavity a few fragments of 

 some light substance, such as cork. The piece of wax 

 is thus between a light body below and a heavy body 

 above. If we wait a few days, this order is reversed 

 — the wax has filled the cavity by conforming to it; 

 the cork has passed through the wajc and appears on 



