Page:Popular Science Monthly Volume 40.djvu/239

Rh and plausible to regard Mount Carmel and the Blue Hills as the source of the ashes and bombs and lava-sheets over by Meriden and up and down the valley.

The Blue Hills have rough slopes to climb, but the view from their tops and the suggestion of past history that one gains there pay for the labor of the scramble. It is easily understood that the rocks are lavas and that they have ascended through the surrounding rocks from some deep source. It is manifest that they did not rise from below when the surface of the country had its present form, for in that case they must have flowed down into the low lands on all sides, and they must have had the slaggy and scoriaceous texture characteristic of surface lavas. One can not doubt that when the lavas of the Blue Hills were placed in their present relation to their surroundings they were deep underground, inclosed by rocky walls on all sides, and heavily pressed upon by the mass above. They forced their way upward from some deep reservoir of molten lava because the push upon them was even greater than the heavy resistance from above. They reached the surface at last, hundreds or thousands of feet above the present summit of the Blue Hills, and there burst out in true volcanic eruption, forming a conical island in the great estuary in which the valley sandstones were formed. We can hardly suppose that they built a grand cone, like Fujiyama, in Japan, twelve thousand feet above sea-level; perhaps they only formed a small mound, like the little temporary volcanic island that appeared in the middle Mediterranean in 1831, called Graham Island, Isle Julia, and Nerita, by its various discoverers. But the Blue Hills were undoubtedly in eruption more than once. This may be safely inferred from the complex network of their pipes and dikes, as well as from the repeated occurrence of lava flows among the series of bedded rocks in the Meriden district. In this respect, as in others, the Blue Hills were like volcanoes of our times. Some of their outpourings were more plentiful than others. Mount Lamentation is part of a lava-sheet whose thickness must be from three to four hundred feet, and whose total original area must have been at least two or three hundred square miles. But the other sheets are not so massive as this one; they indicate eruptions of less energy. While the eruptions were going on there must have been a great scurrying about of the old reptiles whose tracks are found on the sandstone beds at various points in the valley; perhaps the patient searcher may some day find one of their skeletons buried under the ashes of an eruption, just as the old Pompeians have been found buried under the mud and ashes from the outburst of Vesuvius that destroyed their city. During the intervals of rest between the eruptions a luxuriant growth of tree-ferns may have clothed the