There are upon the earth mountainous forms resembling the isolated peaks of the moon, and which have been explained by a similar theory to the above. We reproduce a figure of one observed by Dana at Hawaii (Fig. 37), and a sketch of another observed on the summit of the Volcano of Bourbon, (Fig. 38); we also reproduce (Fig. 39) an ideal section of the latter, given by Mr. Scrope, and showing the successive layers of lava which would be disposed by just such an action as that manifested in the case of the freezing fountain; and we quote that author’s words in reference to this explanation of the formation of Etna and other volcanic mountains. “On examining,” says Mr. Scrope,[11] “the structure of the mountain (Etna) we find its entire mass, so far as it is exposed to view by denudation or other causes (and one enormous cavity, the Val de Bove penetrates deeply into its very heart), to be composed of beds of lava-rock alternating more or less irregularly with layers of scoriæ, lapillo and ashes, almost precisely identical in mineral character, as well as in general disposition, with those erupted by the volcano at known dates within the historical period. Hence we are fully justified in believing the whole mountain to have been built up in the course of ages in a similar manner by repeated intermittent eruptions. And the argument applies by the rules of analogy to all other volcanic mountains, though the history of their recent eruptions may not be so well recorded, provided that their structure corresponds with, and can be fairly explained by this mode of production. It is also further applicable, under the same reservation, to all mountains composed entirely, or for the most part, of volcanic rocks, even though they may not have been in eruption within our time.” To these illustrations furnished from Scrope’s work we add another, copied from a photograph by Professor Piazzi Smyth, of a “blowing cone” at the base of Teneriffe (Fig. 40), which is but one of many that are to be found on that mountain and which has been formed by a process similar to that we have been considering, but acting upon a comparatively small scale. Professor Smyth describes this cone as about 70 feet high and of parabolic figure, composed of hard lava and with an upper aperture still yawning, “whence the burning breath of fires beneath once issued in fury and with destruction.” [Illustration: PLATE XVI TYCHO, AND ITS SURROUNDINGS.]