Page:Popular Science Monthly Volume 14.djvu/102

92 ice either as glaciers or icebergs, or both. A slight inquiry into the nature of aqueous erosion must instantly discredit those views which rely upon its efficacy, and relegate them with the rest to unqualified rejection.

Water, though supplied in torrents so tremendous as to transport the enormous bowlders which are now found scattered so far from their origin, would toss and tumble these masses over the subjacent rock, breaking, fracturing, and denting the latter, but never impressing it with deep, straight furrows for miles, or scoring it with delicate and reticulating striæ.

Again, the numerous pebbles and stones which are found upon and through the topmost soils, in gravel-beds and sand-heaps, would have been smoothly rounded like beach-worn agates, and not, as they really are, tattooed and etched with fine lines running the length of the stone. In the grooves of the rock, and in the fine lines of the pebbles, we have evidence of a body firmly held upon the engraved surface, and passed along with undeviating directness and irresistible power. Prof. Agassiz has traced these flutings upon the rocks of Maine for miles, up hill and down dale, across rivers disappearing upon one side, and reappearing upon the other; and it is beyond possibility to have a plunging torrent of water, charged with stones and rocks, pursue such continuous and definite traces over the hardest rock. More than that, the action of water has been recorded alongside of these very grooves, both in this country and the Alps, as if to invite attention to the opposite character of the two inscriptions. The original traces are firm, direct rulings, and the water-marks beneath them, as in rocky troughs, are waving lines and cracks of denudation following the relative softness of the rock.

Untenable as this theory is, after such considerations, it seems more inadequate when we remember that this element was to transport for leagues masses weighing hundreds and thousands of tons, and to raise them to almost inaccessible altitudes, to arrange them in long succession across intervening slopes. We find, on the contrary, that moderate sized bowlders have sunk to the bottoms of streams, which have removed the soil and lighter material upon which they rested, allowing them, otherwise undisturbed, to sink almost vertically to their beds. Lastly, the high mounds and "horsebacks" associated with this era, composed of unassorted gravel, pebbles, bowlders, and clay, would have been arranged in superimposed layers. Their present composition is almost irrefragable evidence that water had no part in their construction.

On the other hand, the demonstration of the adequacy of the glacial theory to account for these phenomena is found only in a study of those glacial effects which are contemporaneous, or have been witnessed within the memory of man. By establishing an exact accordance between these latter, wherever examined, and the indications of erosion and transportation wide-spread over the continents, we prove the