The question whether the Pleistocene ice-sheets accomplished a large amount of rock erosion has been a fruitful subject of discussion. The most diverse views have been expressed, and there are probably still some geologists who think that the ice executed only a slight superficial scraping and polishing, as well as others who ascribe to it works of such magnitude as the excavation of the basins of the Laurentian lakes. The most important recent contribution is by Goodchild, who shows that the topography of a large district in Scotland, a district largely occupied by sandstones, breccias, and other resistant rocks, was remodeled by Pleistocene ice. Its topography is rugged in detail, comprising many hills and valleys, and these features, instead of conforming in trend to the strike of the rocks, conform to the direction of ice motion, which makes wide angles with the strike.

In line with his conclusions are . . .

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