260 JOHNSTON: ELASTIC BEHAVIOR OF METALS 



ever the need for it became insistent, for the rewards of such effort 

 are considerable. And it is no longer an argument against pro- 

 ceeding to establish relationships in a new field, that the scope 

 of their application cannot be completely foreseen. 



Now, what more promising questions occur to one than these: 

 If the earth was originally fluid, as it appears to have been, and 

 has gradually cooled down to its present state, its component 

 minerals must at some time have been much more thoroly mixed 

 than now; how did they come to separate in the process of cooling 

 into highly individualized masses and groups as we now find them, 

 and what were the steps in their deposition? If the whole earth 

 was hot, whence came the marble of which we have so much and 

 which can withstand no heat? What has given us the valuable 

 deposits of iron, of gold, of precious stones? What determines 

 the various crystal forms found in the different minerals, and 

 what is their relation? Some must have formed under pressure, 

 some without pressure, some with the help of water, and some 

 without. Where is the center, and what the source of energy 

 in our volcanoes? All these questions, and many more, the 

 geophysicist may attempt to answer. 



PHYSICS. — A correlation of the elastic behavior of metals with 

 certain of their physical constants. John Johnston. Com- 

 municated by A. L. Day. 



As is well known, the effect of pressure acting on both the solid 

 and liquid phase of a single substance is to raise or lower its melt- 

 ing point according as the process of melting is accompanied by 

 an increase or a decrease of volume respectively, the latter being 

 the exceptional case. But, when pressure acts only on the solid 

 phase, but not — or not to the same extent — on the liquid phase, the 

 melting point is always lowered and by an amount which is many 

 times as great as the corresponding change produced by the same 

 pressure acting on both the liquid and the solid phase. 



It seemed of interest to calculate the effect of pressure, acting 

 on the solid phase alone, in lowering the melting point of metals, 

 and to compute the amount of such unequal pressure required 



