Page:Popular Science Monthly Volume 40.djvu/238

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226
THE POPULAR SCIENCE MONTHLY.

of the ash-bed ridge, it must be still underground and not discoverable at present. It may be revealed to distant future ages, but to us it is buried. But if the vent lay to the west of the ridge, it may be discovered, not as the cone for which we looked at first, but as a pipe or neck of lava. Indeed, it must in this case be discoverable, for the lava and ashes must somewhere have

PSM V40 D238 Progressive erosion of a volcanic cone.jpg
Fig. 6.

risen from a deep subterranean reservoir, through the country rocks, up to the surface; and if their point of escape lie west of the ash-bed ridge, it must be in sight somewhere. We may not now hope to find the cone where the lavas rose and burst out through the body of water in which the muddy sandstones were accumulating; we can not now hope to discover the crater from which the ashes and bombs were scattered far and wide, and from whose flanks the lava-floods were poured over the low grounds around about it; but we may hope to find a knob or hill where the lava-pipe has been worn down to an undetermined depth beneath the surface on which its cone was built.

This seems to be the fact. Some ten miles southwest of Meriden lie the rugged Blue Hills, one of which is known as Mount Carmel. These may be seen to the west of Wallingford, on the railroad between New Haven and Hartford, or east of Mount Carmel station on the New Haven and Northampton Railroad. They consist of a network of thick necks and dikes of lava; not of loose texture like the ashes, not slaggy like the backs of the lava-sheets, but dense and solid, as if they had been driven there under great pressure. Mount Carmel and its fellows have not the simple outline of the Zuñi buttes; they are of irregular form, corresponding to their complicated structure, as if a compound fracture had been opened to give passage to the ascending lavas, or as if repeated eruptions had forced their way surfaceward at this point, every one increasing the size and complexity of the lava pipes and cracks. There is no other vent of the kind to be found so near to the ash-bed and lava ridges of the Meriden district as Mount Carmel; and while it is entirely possible that a vent may exist at a less distance on the east, concealed beneath the overlying strata in that direction, it is at least permissible