and Soft States in Metals. 261 
arrest of molecular movement or gradually through the 
increasing viscosity of the liquid phase. 
14. The stability of an amorphous solid, depending as it 
does on the curtailment of the tree movements of the mole- 
cules, is obviously determined by temperature. If that 
freedom is sufficiently restored by heat to permit the molecules 
to fall into orderly formation under the direction of polarity, 
the amorphous state will pass over into the crystalline. That 
this degree of freedom is obtained at a definite transition- 
temperature very much below the liquefying-point is abun- 
-dantly shown by the observations which are presented in this 
paper. The stability of the crystalline phase persists from the 
transition-temperature up to the liquefying-point, at which 
point the movement of the molecules can no longer be re- 
strained even under the influence of their cumulative polarity. 
15, The conclusions brought forward in this paper were 
directly led up to by a study of the micro-structure of metal 
and other surtaces, some of the results of which have already 
been communicated to the Royal Society *. In particular 
the discovery of surface-flow during the polishing of cry- 
stalline solids appeared to open up the possibility of a new 
theory of the hardening of metals by plastic flowy. In 
following up this matter a number of experimental obser- 
vations have been made, some of which will be referred to in 
what follows. 
Argument. 
16. Metals ordinarily occur in two distinct solid phases: 
the hardened or amorphous, which will be referred to as the 
A phase, and the annealed or crystalline, which will be referred 
to as the © phase. The A phase is transformed into the 
C phase by the agency of heat, the C phase is transformed 
into the A phase by mechanically-produced flow. In the 
transformations A —— C there are two intermediate mobile 
phases M and M’; so that the transformations may be written 
Bier SL Ciand C => M—=> A. Theargument 
is based on evidence drawn from : 
1. The distinct mechanical properties of the two phases A 
and C. 
2. The micro-structure of these and the evidence which it 
supplies of the existence of the mobile phases M’ 
and M. 
3. The optical properties of the phases A and C. 
4, The electrical properties of the phases A and C. 
5. The thermochemical properties of the phases A and C. 
* Proc. Roy. Soe. vol. Ixxii. pp. 218-225. 
+ Hurter Lecture, Liverpeol, 1903. Soc. Ch, Ind. J. pp. 1166-1177. 
