JOHNSTON: ELASTIC BEHAVIOR OF METALS 265 



of the phenomena observed in the " hardening" of metals, and 

 for the increase of strength following upon deformation. 



Le Chatelier 5 used this conception of unequal pressure to 

 account for regelation— the consolidation of a mass of loose snow 

 at 0° into a block of solid ice. The pressure, due to the superin- 

 cumbent material, lowers the melting point at the surface of 

 contact of adjacent grains by an amount A t. The water formed 

 flows out into the interstices of the snow grains, where it is at a 

 pressure of 1 atmosphere but at a temperature of - A t, and is in 

 contact with ice at 0° ; consequently it freezes again. This process 

 continues until all the interstices are filled up; that is, until a 

 solid block of ice is formed. The behavior of metals under the 

 action of an unequal compression we conceive to be identical 

 with that pictured above for ice. Namely, that metal melts 

 wherever the pressure reaches the appropriate value, flows into 

 the interstices where the pressure is smaller, and solidifies again, 

 with the formation in general of very small crystals, owing to the 

 exceedingly rapid rate of recrystallization. 



This mode of action, besides accounting in an approximately 

 quantitative manner for many of the phenomena observed with 

 metals, is also in harmony with observations on the structure of 

 metal which has " flowed" or has been subjected to deformation 

 of any kind. 



According to Beilby 6 the process of deformation is always 

 accompanied by a partial transformation of the metal to an 

 "amorphous" form, which acts as a cementing material for the 

 untransformed grains. In favor of this view, he adduces evi- 

 dence that there is (a) a difference in the energy content of the 

 strained and unstrained metal, which is manifested in a differ- 

 ence between the two forms, (1) in their electrolytic potential 

 when immersed in a solution, (2) in their thermo-electric power, 

 (3) in their heat of solution; (b) a difference in structure mani- 

 fested in differences in (1) microscopic appearance, (2) mechani- 

 cal properties, — hardness, tensile strength, etc., (3) density, (4) 



5 Z. physik. Chem., 9: 338. 1892. 



6 Phil. Mag. (6), 8: 258-76. 1904. 



