Page:Popular Science Monthly Volume 68.djvu/308

304 in this way were the awful denunciations of an offended God, by the sure extermination of every beast of the field and every creeping thing that crawled upon the face of the earth.

To these causes he believed to be due, not merely the deposits of the coastal plain, but, as well, the barrenness of Labrador and the northeastern portion of the continent, and the general phenomena of the glacial drift, the boulders of the latter being conceived as transported by floating ice.

These essays, it may be noted, were favorably reviewed by Silliman in the third volume of his Journal, even the idea of the fusion of the polar ice-cap being allowed to pass with no more serious criticism than that the flood of waters might have been produced through the expulsion of the same from cavities in the earth. J. E. DeKay, however, writing some years later, ventured to take exception to the views regarding drift boulders, wisely suggesting that, since the speculative part of geology is but a series of hypotheses, we should in every case admit that which explains the phenomena in the simplest possible manner. To his mind the simplest manner of accounting for these boulders was to suppose that such had been, as igneous material, extruded through the superincumbent strata, forming peaks which have since been destroyed through some convulsion of nature or through the resistless tooth of time, the boulders thus being fragments which had escaped destruction, though their place of extrusion had become completely obscured.

The observations thus far recorded display a lack of close attention to details and, in some cases, indicate a decided leaning towards cosmogony. Those to which I now call attention were of quite different type and show their author to have' been a man of more than ordinary discernment.

While superintending excavations preliminary to the erection of a cotton mill at Vernon, Conn., Mr. Peter Dobson observed the boulders in what we now call the ground moraine or till, and in a letter dated November 21, 1825, described them as worn smooth on their under side as if done by having been dragged over rocks and gravelly earth in one steady position. They also showed scratches and furrows on the abraded parts. These appearances he could account for only by assuming that the blocks had been worn by being carried in ice over rocks and earth under water.

These observations seem to have attracted no attention at the time, and even Dr. Edward Hitchcock thirteen years later attached no serious importance to them, although his attention was called to the matter by another letter from Dobson, this time addressed to himself. In this last letter, written in 1838, Dobson described the boulders as having first been rounded by attrition and then worn flat on one side