and Soft States in Metals. 2D 
Note on Flow in Hardened Steel. 
70. In 1890 Mr. C. A. Carus- Wilson * discussed the 
hardening of steel by overstrain, and foreshadowed some of 
the conclusions which are advanced in the present paper. 
His reading of the stress-strain curve of hardened steel as an 
indication of molecular displacement during the progress of 
viscous flow ending in the production of greater resistance to 
stress, which he associated with molecular strain and atomic 
displacement, 1s particularly interesting in the present con- 
nexion. In one passage he says :—“ These stress-strain curves 
indicate the condition of strain as by gradually increased 
stress the steel is converted from an elastic solid to a viscous 
fluid.” While he clearly recognized a stage of viscous flow 
ending in a state in which the molecules were in a state of 
strain, he makes no suggestion as to why the viscous flow 
should terminate ina condition of greater hardness ; or indeed 
why it should terminate at all. 
Note on the Mobile Phase M. 
71. On one occasion [ was, through a fortunate chance, 
able io watch actual movement taking place in a metal 
surface. A piece of copper which contained from 5 to 
7 per cent. of nitrogen had been drawn over the surface of a 
fine Turkey stone. On examining the streak left by the 
copper by normally reflected light with a 4-mm. objective of 
0-95 M.A. and a high-power eyepiece, it was noticed that 
movement of some kind was going on on the surface. By 
careful watching it was seen that the surface was being 
broken up by the issue from the metal of minute gas-bubbles. 
The bubbles were detected by the holes which they left on 
bursting. The holes were from 500 to 1000 wy in diameter. 
The process lasted for fully an hour, during which time the 
appearance of the metal ‘completely changed, the original 
smooth surface having given place to a spongy structure. 
Fortunately a careful record of the observation was made 
at the time, for I have not yet been able to reproduce the 
particular combination of conditions to which it was due. 
The mobility of the metal was evidently caused by the 
passage of the gas from among its molecules (see pars. 46, 
52, and 53). 
72. In 1893 Mr. Thomas Andrews + made a series of expe- 
rimental observations on “‘The Effect of Stress on the Corrosion 
* Phil. Mag. February, 1890, p. 203. 
+t Proc. Inst. C. E. vol. exviii. p. 10 (1894). 
T 2 
