Penny Blood: Serial Sensation and Working-Class Entertainment — page 248: what you’re looking at

Machine-transcribed from the original scan — historical spelling and the odd misread are preserved.

cu. xvul.] THEORY OF VOLCANIC ENERGY. 231 ‘Fransactions. Indeed the experimenter must have felt sur- prised that the cubes were not melted, seeing that the heat Ceveloped ought to have been three and a half times as great as necessary for the purpose. It will also occur to the reader, that Mr Mallet has not made any allowance on account of the latent heat of fusion, but has assumed that, when sufficient heat had been supplied to a mass of rock to raise it to the temperature of fusion, it would become wholly fused. This of course is not the case, because much of the heat would be employed in producing the change of state from solid to liquid, without producing any effect on the temperature. But accepting the conclusion that the heat resulting from crushing one cubic foot could fuse 0°108 of a cubic foot, since this is not capable of fusing the whole of the cubic foot crushed, Mr Mallet considers that this heat may be localized, and that the heat developed by crushing ten cubic miles of rock, may fuse one mile. But it may be conclusively shown that this 1s not possible; for let us consider a horizontal prism of rock of any length. This is itself a part of the earth’s crust, and by its rigidity has, up to the moment of its giving way, resisted, and so permitted, the necessary accumulation of the pressure which eventually causes it to yield. Conceive that in this prism there are portions situated here and there which are weaker than the average, and that these weak portions when crushed allow of the prism being shortened at the places where they are situated by the quantities a,, a,, a,, &c. respectively. It is clear that the weaker places will yield first and under a less pressure, and by the relief so afforded delay the crushing of the others, because the pressure must accumulate afresh. But, for argument’s sake, we will suppose all to yield together, and the pressure throughout the action to be equal to the value it had at the first yielding. Now suppose that when the prism has yielded the whole of it becomes shortened by the length a. If, then, P be the pressure which caused it to yield, Pa will be the whole work done upon the prism. The length a is made up of the portions GOR G OO SS (CO)