Penny Blood: Serial Sensation and Working-Class Entertainment — page 262: what you’re looking at

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

CH. xIX.] THE VOLCANO IN ERUPTION. 245 The ultimate cause of its cessation has been the exhaustion of water-substance in the column of lava. It 1s not by any means requisite however, that the whole of the water-substance shall have been exhausted, or that none shall be passing through the column which still remains in the funnel. This is seen to be the case, because much vapour is continually given off by volcanoes when they are not in eruption, though the quantity 1s incomparably less than what is given off when they are so. According to the formula we have made use of to express the density of the lava, we find that if it rose in the vent, con- taining in its composition the same amount of water with which it started from below the crust, its density at the level of the surface of the crust would be little above that of ordinary water ; for C +9 a-¥) and giving to V the value 0°9 and to - the corresponding value at the surface, which, with o = 2°96, we have found to be 14°4, we obtain for w the value 1°26. And when a volcano 1s in full eruption, and immense volumes of superheated water are passing upwards, it does not seem at all improbable that the mean density of the lava at that level, which will be at the base of the mountain, may be as low as this. Such a low density would agree well with the evisceration of a cone during | , a great eruption, so well described by Scrope’.. We may conclude that a large supply of water is requisite for such manifestations of activity. If so much water must be present in the column to produce an active condition, we can understand how moderate quantities of superheated water passing upwards, although insufficient to cause €ruption, may nevertheless be enough to keep the column of lava, or at least its axis, in a state of fusion. But if the what similar to that which was proposed to explain the phenomenon of a geyser, before Bunsen suggested a better. 1 «¢ Volcanoes,” p. 186. CONNEC OOO @ (CO)