Since the establishment of the glacial theory the cause of the hummocky and roches moutonnées character of the rocky surface of the Archean terranes of North America has generally been ascribed to the action of the ice of the glacial epoch. Two opinions have been prevalent, having this belief as their basis. The first and older view was, in accordance with the theories promulgated by the Scotch geologists, that the hummocks and their complementary hollows were produced by the direct plowing or gouging action of glacier ice loaded with rock débris. The second and more modern view is, that just as south of the terminal moraine we find the crystalline rocks extensively decomposed in situ, so prior to the advent of the glacial epoch the Archean terranes of the north were similarly decomposed, and the present hummocky surface represents the locus to which rock decay had extended in . . .