Physical and Chemical Behavior of Solids. 221 



a large number of observations, which demonstrate the exist- 

 ence of important differences between metal which has 

 "flowed," or has been subject to deformation of any kind, and 

 the same metal in the annealed condition. All the available 

 evidence* goes to show that there is: (a) a difference in the 

 energy content of the strained and unstrained metal, which is 

 manifested in a difference between the two forms (1) in their 

 electrolytic potential when immersed in a solution, (2) in their 

 thermoelectric power, (3) in their heat of solution ; {b) a differ- 

 ence in structure, manifested in differences in (1) microscopic 

 appearance, (2) mechanical properties — hardness, tensile 

 strength, etc., (3) density,f (4) conductivity for heat or elec- 

 tricity, etc. For any one metal these differences vanish about 

 a single temperature common to all — that is, at the tempera- 

 ture at which annealing proceeds with appreciable rapidity. 



According to Beilby,;}; the process of deformation is always 

 attended by a partial transformation of the metal into an 

 " amorphous "§ form; according to Faust and Tammann,|| on 

 the other hand, the change of properties on deformation is 

 parallel to the production of smaller crystallites. Whichever 

 be the correct interpretation — if indeed these views are mutu- 

 ally exclusive — the fact remains that deformation of a metal is 

 attended by changes in its properties. These changes are such 

 that they would be difficult to account for reasonably, except 

 by the very simple supposition that an actual melting has 

 occurred. 



Further evidence in support of the view here advocated is 

 presented in the paper above referred to ; enough has been 

 presented here, we hope, to demonstrate the plausibility of the 

 idea that any permanent deformation of a crystalline substance 

 is determined by an actual melting of some part of the 

 material — a melting which occurs as soon as the local stress 

 reaches the melting pressure corresponding to the temperature 

 of the mateiial. 



In what follows we shall make use of this conception to 

 interpret the observations of those who have investigated the 

 effect of high pressure upon solid systems : and hope to dem- 

 onstrate that by the use of well-known criteria in conjunction 

 with this conception the various observations can be recon- 

 ciled ; which will enable us then to give a consistent account 

 of the present status of the question. 



*Cf G. T. Beilby, Phil. Mag. (6), viii, 258-76, 1904, who discusses the 

 evidence in detail 



f These differences have been discussed in detail by the authors in a 

 previous paper. J. Am. Cheni. Soc, xxxiv, 563, 1912. 



X Loc. cit. 



§ Beilby here uses the term " amorphous " to denote a heterogeneous 

 assemblage of molecules. 



|| Zs. phys. Chem., lxxv, 108-26, 1911. 



Am. Jour. Sci.— Fourth Series, Vol. XXXV, No. 207.— March, 1913. 

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