Penny Blood: Serial Sensation and Working-Class Entertainment — page 140: what you’re looking at

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

CH. X. | DISTURBED TRACT. 123 assume some function to express the value of f which has a constant value > at the surface, and decreases, at first slowly, and afterwards more rapidly, as the depth @ is increased. For the purpose in hand we may admit that it becomes zero at the bottom of the crust, although this is of course not strictly true. An appropriate function for our purpose appears to be, : d cos 5 The corresponding force upon an element at P will there- fore be cos = Ok ~ daz; and the whole frictional force upon AZ will be . 7H ; cos oe dz, 2k . wh or, A — — sin oh If we make 2 =k, we find the friction across the whole crust to be A = . And it 1s evident that the friction along AZ, plus the friction along ZB, make up the whole friction across AB. Hence the friction along ZB =X = (1 — gin mys. Our condition for the position of the neutral zone then gives us, oF i wh = . mh in Te 1 or 8 oh 2” wh 1-7 ' Ok =3 2? 1 GONG oOo SS (CO)