Penny Blood: Serial Sensation and Working-Class Entertainment — page 55: what you’re looking at

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

38 LATERAL PRESSURE, ITS AMOUNT. [cu. 1Vv. likely to be crushed under the circumstance of a contraction of the mass beneath. Suppose that, on a unit of area, P is the pressure towards the centre at a distance r from the centre, caused by so much of the weight of the superincumbent rock as is sustained by the next inferior stratum (which is supposed not to be yet crushed). Then, if we consider the effects of the crushing of the rock above it to be uniformly distributed, P cannot be so great as the pressure which would arise from the same rock were it fluid, because part of the weight of the crushed rock will be sustained by latera] pressure. Hence if we consider the conditions of equilibrium of an element of the stratum in question lying next beneath the rock which produces the pressure P, and suppose this shell and the superincumbent mass to be in equilibrium without resting upon the interior mass, we shall be able to calculate the horizontal pressure which tends to crush the shell. Let Z” be the horizontal pressure upon a unit of area of ‘any vertical section of this shell, r’ the thickness of the shell, and g’, p’, the values of g, p, at that depth. Then we shall have, by the same reasoning as in ‘the pre- vious proposition, T's’ = (P+9'p'r') 5. Let us compare this horizontal pressure 7” with the cor- responding pressure 7' at the surface, which has been shown to be equal to gp 5 T'>=<T. — Ptget ry gpa As Pr>=< (gpa-—g'rr)r. As P>=< (27 2P 9), IP \ 7. gp Let y be the depth of a column of rock of a unit of section and density p, whose weight at the surface would equal the commiclsoolkks ee eel (C@ __) _) —_—— wa