Penny Blood: Serial Sensation and Working-Class Entertainment — page 212: what you’re looking at

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

cu. xv.] COMPRESSION AND VOLCANIC ACTION. 195 the fissure. If we substitute the values already found for 8 and a in this equation, 1t becomes 1 (Vp* ae + gpk (1— V) p= | pda. Now at the bottom of the crust p=gpk, and putting V=09 we have found that the value of p at the surface gpk P _ n.onx will be 14-4; And 5 7 9908. Using these values at the limits we obtain k gpk? x 0-489 = | pda. 0 And if we give to k the value 25 miles , ke gp X 12°2 miles =; / pde. 0 That is to say the mean horizontal pressure of the lava throughout the vertical section is equal to what would be produced by the weight of a column of the crust rather more than 12 miles high. The work done by the compressing force in raising a moun- tain chain (which we use as a generic term for any elevated tract) will consist of two parts, (1) the work producing deforma- tion of the crust, which will include the work of distortion and cleavage, and is done against the molecular forces, and (2) the work done against gravity. This last will in itself consist of two parts, viz. the elevation of the mass of the mountain above the upper mean level of the crust, and the depression of its root into the fluid, below the lower mean level. If we take y=f(J) to define the contour of the elevated mass along a section across the tract, the work against gravity on a section of unit of width will be y" gp | 5 dl. And similarly, if y’ be the ordinate corresponding to y for the root of the mountain below the lower mean level, the 13—2 GONG oOo SS (CO)