Penny Blood: Serial Sensation and Working-Class Entertainment — page 263: what you’re looking at

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

246 THE VOLCANO IN ERUPTION. [ou. xrx. means of supply of water-substance be more liberal, and be just balanced by the means of escape, a gentle and perpetual state of eruption like that of Stromboli, may result. That the main- tenance of the temperature of fusion in a habitual vent is due to the cause suggested, appears probable from the following consideration. Molten lava sometimes fills the bottom of a crater for a long period, its surface being maintained in a con- stant state of ebullition by the vapour and gases which pass through it. In such a case it must be the high temperature of these vapours which keeps it melted: for if the fusion were due to a continual supply of fresh lava from below, there would need to be a continual escape of it above. But this does not appear to be requisite. If such be a correct view of the case, it shows that the hot vapours are capable of fusing rocky matter, and accordingly, when once they have obtained a passage of escape, they may convert the sides of the channel into lava and fuse their own way through, carrying the fused matter with them’. It has been often urged that volcanic vents cannot com- municate with a common reservoir below, because, even in the same mountain, contiguous craters are not sympathetic. But this sympathy does not seem really necessary, for as soon as a column of ascending vapour has established itself in one crater, the tendency will be for it to continue to hold the same position, since its presence renders that the vertical of least pressure, and consequently the channel of easiest escape. We see the same sort of thing take place when water begins to boil in a vessel heated below. Before it passes into general ebullition, a column of bubbles will appear here and there, and rise from the same points of the bottom of the vessel for a considerable time. So, when the escape of vapour has commenced through one of the craters, it may carry off the vapour as fast as it is supplied, and determine the eruption to that channel, the neighbouring crater remaining quiescent, although they may both of them be in free 1 See the author's paper ‘“‘On the Inequalities of the Earth’s Surface upon the hypothesis of a liquid substratum.” ‘Camb. Phil. Trans.,” Feb. 1875. COMIC MOOOLKS @ (CO)