264 JOHNSTON: ELASTIC behavior of metals 



together all the data available on the elastic properties, namely, 

 compressibility, hardness, tensile strength, elastic limit, elastic 

 modulus, and modulus of rigidity. 



From this table it is evident that as the value of <p increases, 

 the compressibility decreases, and the values of the other elastic 

 properties increase steadily. The exceptions to this statement 

 are very few as regards any one property, and vary irregularly 

 as we pass from one property to another; in other words, there are 

 no systematic divergences between the sequence of the metals 

 as derived from the thermodynamic relationship discussed in this 

 paper, and that obtained when they are arranged progressively 

 with reference to any one of their elastic properties. The slight 

 divergences are no greater than one might expect from the uncer- 

 tain character of the thermal data, on the one hand, and of the 

 elastic constants on the other. 



From the above, then, it appears to be true that the mechanical 

 properties of metals are correlated with the amount of pressure — 

 assumed to act on the solid alone — requisite to cause the metal 

 to melt at or near the ordinary temperature. This pressure in 

 turn depends upon the melting point, the density, and the heat 

 of melting, of the metal. The first two of these quantities are 

 known to be periodic functions of the atomic weight, and there is 

 every reason to believe that the heat of melting, and therefore 

 also <p, is. Therefore we should expect some, or all, of the elastic 

 properties to be periodic functions. So far, thoro measurements 

 have been made only on the compressibility, which, according to 

 Richards, shows marked periodicity. 



The remarkable concordance shown in the above table, which 

 can hardly be due to coincidence, indicates that the "flow" of 

 metals — or indeed, every permanent distortion of a crystalline 

 solid — is due to an actual fusion and resolidification of the crystals. 



These considerations may also be used to throw light on the 

 general behavior and properties of metals, and on many geological 

 phenomena; but it would lead too far to go fully into these matters. 

 We wish, however, to give briefly a mechanical picture of the 

 probable mode of action of unequal pressure upon a metal, and 

 to indicate how such an explanation accounts plausibly for many 



