Ragnarok : the age of fire and gravel

THE CONSEQUENCES TO THE EARTH. 103

described as lustrous. The heat may not have been great enough to melt them—it may merely have softened them ; but when the mixture of clay, gravel, striated rocks, and earth-sweepings fell and rested on them, they were at once hardened and almost baked ; and thus we can account for the fact that the “till,” which lies next to the rocks, is so hard and tough, compared with the rest of the Drift, that it is impossible to blast it, and exceedingly difficult even to pick it to pieces; it is more feared by workmen and contractors than any of the true rocks.

Professor Hartt shows that there is evidence that some cause, prior to but closely connected with the Drift, did decompose the surface-rocks underneath the Drift to great depths, changing their chemical composition and appearance. Professor Hartt says:

“Tn Brazil, and in the United States in the vicinity of New York city, the surface-rocks, under the Drift, are decomposed from a depth of a few inches to that of a hundred feet. The feldspar has been converted into slate, and the mica has parted with its iron.” *

Professor Hartt tries to account for this metamorphosis by supposing it to haye been produced by warm rains! But why should there be warm rains at this particular period? And why, if warm rains occurred in all ages, were not all the earlier rocks similarly changed while they were at the surface ?

Heusser and Clarez suppose this decomposition of the rocks to be due to nitric acid. But where did the nitric acid come from ?

In short, here is the proof of the presence on the earth, just before the Drift struck it, of that conflagration which we shall find described in so many legends,

* “The Geology of Brazil,” p. 25.