Penny Blood: Serial Sensation and Working-Class Entertainment — page 267: what you’re looking at

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

250 SEQUENCE OF VOLCANIC ROCKS. [cu. xx. slow, and there will be a tendency for the two fluids to become mingled in varying proportions according to circumstances. If the fused rock creeps along the top, itself in contact with the under side of the crust from which it has been derived, its com- position on the upper side of the flow will be little altered, but on the lower side it will be more or less mingled with the sub- stratum, owing to the friction between the two. There can be no doubt that there will be sufficient heat in the substratum for the above purpose, because the magma, even after the water which it contains has been blown off in vapour, and so carried away a vast amount of heat, retains sufficient heat to afford liquid lava. There must therefore be heat to spare in the substratum to melt matter off the roots without it- self becoming congealed. It will be desirable to compare the force which urges the fused rock up the inclined root, with that which would urge a liquid down the incline at the point vertically above it on the surface of the mountain. Let @-be the angle of inclination to the horizon at a point on the side of the mountain at a height 2 above the mean level, and let 6 be the angle of inclination to the horizon at the point vertically beneath it upon the side of the root at the depth h’ below the lower mean level. And suppose, as usual, that W’=—P_ hp, o—p Neglecting the thickness of the crust, which is immaterial to the demonstration, the tangents at these two points will meet at the same point in the crust. This follows because h' bears a constant ratio to A. Let J be the distance from: the common ordinate h +h’, where the tangents meet. Then, resolving the forces along the two tangents, we have, Force below (¢— — Pp) gsin Force above | gsin®@ JO +h ao Stree COMIC OOOKS.EO