Penny Blood: Serial Sensation and Working-Class Entertainment — page 188: what you’re looking at

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

CH, X111.] AMOUNT OF COMPRESSION. 171 If we revert to the datum level equation (1) in the fifth chapter’, which is perfectly general for a vertical section of the crust under compression, and adapt it to volumes, as has been done in equation (3)’, but retaining terms answering for volumes to & (a) and 2 (8) in equation (1), which terms we will call > (X) and & (VY), we then have, 8arke => (A) —% (B)+% (Y)—% (X), for our general datum-level equation of volumes for a solid crust resting on a fluid substratum. And we know that in this expression >(Y)—%(X)=0. In this equation it will be recol- lected that eis the mean linear compression of the crust, and that the surface above which the volumes %(A), and below which the volumes % (B), are reckoned, is the imaginary surface which occupies the position that the upper surface of the crust would occupy at the present time, had it been perfectly com- pressible in a horizontal direction ; and that }(X) and %(Y) are the volumes similarly situated with respect to the lower surface of such a crust®, Let us now transform this equation to the upper and lower “mean levels” of the crust, which by the defi- nition will be at the same distance apart as the datum levels". In the same manner that A, B, X, Y are referred to the datum levels, let A’, B’, X’, Y’ be referred to the mean levels; and, in the figure, let in the first place the outer circle be the lower mean level, and the inner one the lower datum level ;. lp. 47, 2 p. 50. 3 p. 48. + p. 115. COMMUC NOO SS (CO)