Penny Blood: Serial Sensation and Working-Class Entertainment — page 138: what you’re looking at

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

CH. x.] DISTURBED TRACT. 121 circumstance will therefore be determined by the resistances which operate to resist the motion of the element in question. These will be the weight of the element acting downwards, the friction tending to resist the motion, and opposite to it in direction, and the pressure of the crust upon the fluid beneath. It 1s evident that the friction among the particles of the crust will depend upon its physical state. If it were rigid it would be infinite; if liquid it would be zero. As it is, we may conclude that its plasticity 1s increased in the lower parts by the influence of the high temperature there. We will therefore assume the friction to be some function of the depth. It will be sufficient for our purpose to consider the density constant throughout the thickness of the crust. Let then AB=k be the thickness of the crust before motion commences. When the lateral pressure has become so great A that compression begins to take place, suppose that the portion AZ of the column AB is sheared upwards, and the portion ZB downwards, and let us call the locus of the point Z the “neutral zone.” Let p be the force at P which resists the upward motion of the element PQ; AP=a2, PQ=dz, f=the frictional force, which we assume to be a function of 2. | Then dp =gpda + fdx ; p=gpx+ | fan +C. GONG oOo SS (CO)