Penny Blood: Serial Sensation and Working-Class Entertainment — page 250: what you’re looking at

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

cH. xvi] THEORY OF VOLCANIC ENERGY. 233 on increasing until one of these places gives way. Let P, be a general symbol for this increasing horizontal force, measured by the pressure, in terms of the weight of a cubic mile of mean rock at the surface, upon a square mile of vertical section of the crust. Now it is evident that no greater lateral shortening, or ap- proach of the particles of the crust among themselves, can take place at one place than at another, except through a lateral movement of the layers of the crust over the nucleus towards the place in question. Hence any localization of work at a given place must require this to occur more or less, Conse- quently if the pressure goes on accumulating until it becomes equal to P, all round, and under that pressure the crust begins to yield at A, the yielding there cannot relieve the pressure anywhere else, unless the crust is shifted over the nucleus towards A. Having premised thus much, we will endeavour to find the utmost amount of heat which could be developed along a vertical section at any one place in the crust. Conceive a strip of the crust, one mile in width, situated along a great circle; and suppose the pressure to have gone on increasing to some value P,, which has caused the crust to yield B A B’ ee at A; and that by such yielding the pressure has been reduced to P, at A, and partially relieved over 4B and AVF on either side of A, but not just beyond B and B. Hence at B, B the pres- sure will still be P,. Somewhere beyond B and B' it will have been relieved by yielding at other places; and it is supposed that it does so yield all round, so as to fit the reduced nucleus, Hence the amounts to which the pressure will accumulate at different places will depend upon the strength of the crust; but the amount of shortening of the whole crust will not depend upon the amount of the pressure, but solely upon the amount of contraction of the nucleus. Consequently if e be the coef- ficient of linear or radial contraction, seeing that the points GONG oOo SS (CO)