Penny Blood: Serial Sensation and Working-Class Entertainment — page 222: what you’re looking at

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

exw. xv.| COMPRESSION AND VOLCANIC ACTION. 205 been transmitted across such fissures filled with fluid, nor could they have supported a pressure propagated from the further side of the elevated tract, so that the intervening region could have been compressed. According to the suggestions offered in the present chapter to explain the compression of the crust, the store of energy from which the mechanical force is derived resides (1) in the heat of the interior, and (2), if we refer any part of it to expansion of the rocks on solidifying, in the molecular force attending a change of state; while in the theories discussed in the former chapters the force is derived from the gravitation of the crust towards the centre of attraction of the globe. This latter force is practically infinite compared with the work it would have to perform in shearing the crust, but it has been shown that the hmit to the space through which it can have acted, owing to the small amount of the globe’s contraction, is so quickly reached, that it cannot fully explain the pheno- mena. The case is entirely different with regard to the theory now suggested. Here the force (1) is limited, since it never can exceed, or indeed practically reach, the pressure of a column of the earth’s crust, viz. about 23,547,900 pounds, or 10,066 tons, upon the square foot, but there is no limit to the space through which it might act, so long as the fissures did not reach the surface. The limit imposed is the resistance which the crust offers to shearing. And it is probable that this may have been reached, where a tract has been thickened to such an extent, that its surface has been elevated to the normal height of the highlands of the globe. The direction orthogonal to a fissure in which motion would take place when the crust yielded, would depend upon its rigidity; and it 1s conceivable that, although thicker beneath continental areas, it may be weaker there, because less homo- geneous and less dense; and we know that surfaces of rupture, once formed and faced with slickenslide, are ready prepared for repeated movements. If such be the case, the tendency would be for compression to take place in the direction from the shore margin towards the mountain ranges. The latter being continu- ECONNIE OOO SS (CO)