GRAVISTATIC HEAT 333 



ings. As in the case of the vacuum-tube experiment they 

 blindly prejudge the issue. 



But let us reason the thing out in a common-sense 

 way. Suppose the experiment to have taken place up to 

 the point where the lead is liquefied, in the cylinder, and 

 still under the full pressure of the piston. We will now 

 assume, to begin with, the possibility that, given time, the 

 lead will cool off and become solid, notwithstanding the 

 continuance of the pressure. At this latter stage imagine 

 the piston to be undamped completely and then immedi- 

 ately reclamped with precisely the same effort as in the 

 first instance, what effect will the proceeding have on 

 the lead? Will the latter be liquefied afresh? How so? 

 Surely the second clamping, by merely restoring the 

 former conditions, cannot compress the ingot to less com- 

 pass than before ; and without accomplishing this much, 

 according to general acceptation, the lead must remain 

 in the solid state. Alternatively, suppose the metal in 

 this case should nevertheless become liquefied; then in 

 the name of reason why did it not stay liquid in the first 

 place. Again, if no change at all should occur and the 

 ingot under the second application of the pressure re- 

 tained its solidity just as it was immediately prior to the 

 moment of unclamping, then all the energy expended in 

 the second act, though by premiss precisely the same as 

 in the first, would be utterly lost, not being compensated 

 by any increase of temperature whatsoever in the lead. 

 Shall we then precipitately conclude that, given a particu- 

 lar mass of lead that has once before been liquefied by a 

 certain intensity of pressure, it can never again be lique- 

 fied save by a higher pressure than other lead samples 

 would require; resulting at the end of a series of such 

 steps in a specimen of the metal altogether impervious 

 to compression? Such a conclusion cannot be true, 

 surely, for it would be tantamount to saying that gold is 

 not always gold, lead not always lead, nor iron always 

 iron. 



When Proctor, therefore, speaks of a cubical iron 

 mountain being able to liquefy its base, and when the 



