Page:Geological Evidences of the Antiquity of Man.djvu/381

Rh, and the intervening valleys, the hypothesis of glaciers is out of the question. I conceive, therefore, that the erratics were conveyed to the places they now occupy by coast ice, when the country was submerged beneath the waters of a sea cooled by icebergs coming annually from arctic regions.

Suppose the highest peaks of the ridges in the annexed diagram, to be alone above water, forming islands, and d e to be masses of floating ice, which drifted across the Canaan and Richmond valleys at a time when they were marine channels, separating islands, or rather chains of islands, having a NNE. and SSW. direction. A fragment of ice such as d, freighted with a block from, might run aground, and add to the heap of erratics at the NW. base of the island (now ridge), or, passing through a sound between and the next island of the same group, might float on till it reached the channel between and. Year after year two such exposed cliffs in the Canaan range as d and e of the map, fig. 50, p. 357, undermined by the waves, might serve as the points of departure of blocks, composing the trains Nos. 5 and 6. It may be objected that oceanic currents could not always have had the same direction; this may be true, but during a short season of the year when the ice was breaking up the prevailing current may have always run SE.

If it be asked why the blocks of each train are not more scattered, especially when far from their source, it may be observed, that after passing through sounds separating islands, they issued again from a new and narrow starting