Page:Popular Science Monthly Volume 40.djvu/234

222 the eruption, arriving here before the ashes, plunging down after its lofty flight through the air, and sinking into the mud at the bottom of the water. In this it recalls the reptilian footprints that have made the sandstones of the valley famous. The old reptiles walked over the mud-flats and left their heavy prints on the surface to be buried under the next layer of mud; the lava block fell into the soft sandy mud and made its print, where it still lies. Long may it rest undisturbed! A poor indication of it is presented in Fig. 1, copied from a photograph by a friend in New Britain, Conn. All this was much more evident and more easily interpreted than those who try to learn geology from books are disposed to believe. Indeed, one of the students with me exclaimed: "This is the most realistic thing I ever saw; I had no idea that it could be so plainly made out." The ledge has been visited by hundreds of persons from Meriden and the surrounding towns, and a well-beaten path now leads up to it from the road. I have taken parties of students there every summer since then, and hope to do my share toward beating down that path for many years to come. But although the meaning of the ash-bed is plain enough, there is a question suggested by it that is not so easily answered. Where is the volcano from which the ashes and bombs were blown out?

The same question has arisen in other countries. For example, in central France, in Auvergne, there are chalky beds that were once a soft white mud, and in these lie bombs of lava, bending down the layers on either side; manifestly again the result of a bombardment from some adjacent volcano. In the same district there are beds of ashes and flows of lava, all indicating volcanic outbursts in their vicinity; but when the question is there asked—Where are the volcanoes from which these products came?—it is easily answered, for many volcanic cones still stand up in plain sight near by; the lava-flows may be traced up to their bases, the craters are still visible at the summits, and although no record exists of their eruptions, it is manifest that at a relatively recent prehistoric period these cones exhibited a brisk activity. I walked over them a dozen years ago; they make a delightful strolling and sketching ground, and I remember well lunching with a shepherd on one of their sunny slopes, and answering his questions about distant America (Fig. 2).

We may look in vain for volcanic cones in the neighborhood of our Meriden ash-bed bluff. There are hills and ridges all around, but nowhere can we see the smooth and characteristic concave slopes of a volcanic cone. To the south, there are several symmetrically rounded hills, but they are convex, not concave, on the side, and an examination of the road-cuts made in their slopes shows them to be of anything but volcanic origin. They are "drumlins," hills