THE LIFE OF MATTP]R. 411 



tiiiiGs less, theii- prol);il)le velocity woukl he, as re((uire(l by tiie kiiu'tic 

 theory, some hundreds of- milKnieters per seeoiid. The Browiiiun 

 velocity of the smallest objects we can perceive is l)iit some thou- 

 sandths of a millimeter per second. Doubtless, concludes ]\I. (Jouy, 

 the particles that show this movement are really enormous when com- 

 pared with true molecules. Looked at in this way, the Hrownian 

 movement is ])ut the tirst degree and a gross manifestation of the 

 nioleculsir \ibrations which th<» kinetic theory sup})oses. 



3. THE INTESTINAL A(^TI\ITY OF ]U)1)IES. 



Mkjrat'uni of inaferidl p<uiivlix. — In the Brownian movement wo 

 take into account only very siuall, isolated masses, small free frag- 

 ments; thitt is to say, material particles which are not hampered by 

 their relations to neighboring particles. Any cither but a physicist 

 might believe that in true solids endowed with cohesion and tenacity 

 in which the molecules are l)ound one to the other, in which the form 

 and th(» volume are Hxed, then^ could l)e no longer any movements or 

 changes. This is an error. Physics teaches us the contrary, and, 

 especially in these latter j^ears, has furnished us characteristic exam- 

 ples. There are veritable migrations of material ])articles throughout 

 solid bodies — miorations of consideral>le extent. Thev are accom- 

 plished through the agency of diverse forces acting from the exte- 

 rior — pressures, tractions, torsions — sometimes under the action of 

 light, sometimes under the action of electricity, sometimes under the 

 intiuence of forces of diffusion. The microscopic observation of alloy's 

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

 J.-K. Benoit; the studies of their physical and chemical properties by 

 MM. Calvert, Matthiessen, Riche, Roberts Austen, Lodge, Laurie, 

 and Ch.-Ed. (uiillaume; the experiments in the electrolysis of glass, 

 and the curious results of Bose upon the electric touch [tact-electrique] 

 of metals show in a striking manner the chemical and kinetic evolu- 

 tions which occur in the 'interior of bodies. 



]\f!<jr((f!())i iindrr the ijirfJnence of irc/(jJit. — An experiment of 0])er- 

 meyer which dates from 1877 furnishes a good examj)le of the migra- 

 tions of solid bodies through a hardened viscid mass under the influence 

 of weight. Shoemaker's wax, the black wax that shoemakers and 

 boat builders use, is a kind of resin extracted from the pine and other 

 resinous trees, melted in water, and separated from a more fluid part 

 which rises above it. It is colored by the lampblack produced by the 

 combustion of straw and fragments of bark. At an ordinary temper- 

 ature it is a mass so hard that it can not always be indented easily 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 wax and keep it there by means of a few pcb- 



