THE LIFE OF MATTER. 413 



i\I. Brillouin has a^'ain tHkeii up this hypothesis of (hiaiity of stiucture. 

 The metal is supposed to b^ foiHued of very small, isolated, (nystallinc 

 oiaius embedded in an almost continuous netwoi'k of viseous matter; 

 a more or less compact mass surrounding more or less distinct crys- 

 tals is the conception which may be formed of an alloy. 



ChatK/t's of struct u t')' 2)i'odueed hy defoi'tii'nxj (((/mdcx. — It has l)een 

 shown that profound chano-es of crystalline structure can be produced 

 by \ arious mechanical means, such as hammering and the traction of 

 metallic bars carried as far as rupture. Some of these changes are 

 \ cry slow, and it is only after months and y^ears that they are completed 

 and the metal attains the definitive equilibrium corresponding to the 

 conditions in which it is placed. Tliough there may be disi-ussions 

 concerning the nature of the transformations to which it is subjected, 

 though some believe they affect the chemical condition of the alloy, 

 while others limit its power to physical effects, it is nevertheless trui; — 

 and this brings us back to our sul)ject — that the mass of these metals 

 is at work and that it only slowly attains the phase of complete repose. 



TJie .slow reestahllslMnent of equlllhrlioii — Hesidiud ejf'txt. — These 

 operations by which the physical characters of metals are changed, 

 and by which they are adapted to a variety of industrial needs — com- 

 pression, hanuuering, rolling, traction, and torsion — have an inunedi- 

 ate, \Qvy apparent effect; l)ut they have also a consecutive effect, 

 slowly produced, much less marked and less evident. This is the 

 residual effect or "Nachwirkung" of the Germans. It is not with- 

 out importance even in practical applications. 



Heat also creates a sort of forced equilibrium. This becomes but 

 slowly moditied, so that a body ma}^ remain for a long time in a state 

 which is nevertheless the uiost stable for the conditions under which 

 it is considered. The number of these bodi(\s out of e(|uilil)rium is as 

 great as that of the matters which have been submitted to fusion. 

 All the Plutonian rocks are in this condition. Glass pres(Mits a simi- 

 lar one. Thermometers placed in melting ice d(^) not always mark the 

 z(Mo of centigrade. This displacement of the zero point falsities all 

 their indications if care is not taken to correct it. This correction 

 usually demands a long observation. The theory of the displacement 

 of the thermometric zero is not entirely established, but we may sup- 

 pose with the author of the Traite de Thermometrie that thei'(> exists 

 in glass, as in alloys, compounds which vary according to the tempera- 

 ture. At each temperature glass tends to assume a determinate com- 

 position and a corresponding state of equilibrium, but the pixnious 

 temperature to which it has been subjected has e\idently an influence 

 upon the rapidity with which it attains its state of repose. The effect 

 of vai'iation is more marked as we ol)ser\e glasses of luore complicated 

 composition. We can readily understand that those which contain 

 comparable (quantities of the two alkalies, soda and potash, may be 



