Penny Blood: Serial Sensation and Working-Class Entertainment — page 204: what you’re looking at

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

cH. xv.] COMPRESSION AND VOLCANIC ACTION. 187 produced by any cause in the under surface of the crust. The pressure of the fluid at the bottom of the crust is that due to the weight of the superincumbent crust, and consequently the tension of the water-substance in the magma there must be the same, If therefore, upon the opening of a fissure which did not reach the upper surface, the magma beneath were able to fill it with water-substance, which we may provisionally call vapour’, at a tension equal to the pressure which it sustains from the weight of the crust (about 10066 tons upon the square foot), the fused rock could not rise into the fissure at all, but the sides of the fissure would be subjected to a vapour pressure, only less than the pressure of the entire crust by the diminution upwards due to the decreasing weight of the superincumbent vapour, which, compared with its tension at the bottom of the chasm, would be inconsiderable. Thus we should under the circum- 4. uy ata. stances supposed (which could never be fully realised) have a + «-,.-¢ horizontal pressure upon every elementary area of the sides of w%s< \vs> the chasm equal to the weight of a column of rock of the same Wheres sectional area and about 25 miles high. Generally, let ¢ be the tension of the water-substance which occupies the chasm, # the height to which the magma rises in the chasm, then, if we neglect the weight of the water-substance bres ane <r i. i . a : > L { * i : 0 + t 1 oui compared with that of the magma, which owing to its high temperature we are probably justified in doing, t = gpk — gah. This will be the horizontal pressure upon the side of the fissure everywhere above the surface of the fluid magma in the fissure, 1 Perhaps it ought rather to be called gas. See Hannay ‘$On the states of matter,” Proc, Royal Soc,, Vol. xxxt1. p. 412. 1881, COMiCOOokxS.conn @