[1. “The Great Ice Age,” pp. 70-72.]
the moraine profonde in their softness, and the large area which they cover. Strata of bowlder-clay at all comparable to the great clay mantle covering the lower grounds of Britain, north of the Thames, are conspicuous by their absence from the glaciated regions of Central Europe and the Pyrenees, which were not depressed beneath the sea.”
A RIVER ISSUING FROM A SWISS GLACIER.
Moreover, the Drift, especially the “till,” lies in great continental sheets of clay and gravel, of comparatively uniform thickness. The glaciers could not form such sheets; they deposit their material in long ridges called “terminal moraines.”
Agassiz, the great advocate of the ice-origin of the Drift, says:
“All these moraines are the land-marks, so to speak, by which we trace the height and extent, as well as the
[1. Dawkin’s “Early Man in Britain,” pp. 116, 117.]
progress and retreat, of glaciers in former times. Suppose, for instance, that a glacier were to disappear entirely. For ages it has been a gigantic ice-raft, receiving all sorts of materials on its surface as it traveled onward, and bearing them along with it; while the hard particles of rocks set in its lower surface have been polishing and fashioning the whole surface over which it extended. As it now melts it drops its various burdens to the ground; bowlders are the milestones marking the different stages of its journey; the terminal and lateral moraines are the frame-work which it erected around itself as it moved forward, and which define its boundaries centuries after it has vanished."
And Professor Agassiz gives us, on page 307 of the same work, the above representation of a “terminal moraine.”
The reader can see at once that these semicircular
[1. “Geological Sketches,” p. 308.]
ridges bear no resemblance whatever to the great drift-deposits of the world, spread out in vast and nearly uniform sheets, without stratification, over hills and plains alike.
And here is another perplexity: It might naturally be supposed that the smoothed, scratched, and smashed appearance of the underlying rocks was due to the rubbing and rolling of the stones under the ice of the glaciers; but, strange to say, we find that—
“The scratched and polished rock-surfaces are by no means confined to till-covered districts. They are met with everywhere and at all levels throughout the country, from the sea-coast up to near the tops of some of our higher mountains. The lower hill-ranges, such as the Sidlaws, the Ochils, the Pentlands, the Kilbarchan and Paisley Hills, and others, exhibit polished and smoothed rock-surfaces on their very crest. Similar markings streak and score the rocks up to a great height in the deep valleys of the Highlands."