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of a Colorado Canyon. The objections to ice as an agent of profound erosion remind one very much of the objections which, in the early days, were urged against water as an agent of erosion. In this connection reference may be made to a short note, signed H. G., on page 249 of the National Geographic Magazine, Vol. 16, 1905. This little squib, which we may fairly safely ascribe to Henry Gannett, although written in a humorous and somewhat sarcastic vein, is really a noteworthy contribution to the discussion on glacial erosion. In it, as a sort of reply to a recent arraignment of glacial erosion, he applies to the now accepted belief in river erosion some of the same class of arguments as those which have been urged against glacial erosion, and with telling effect.

Since the establishment of the theory of profound glacial erosion is the work of the last fifteen years, and since the full force of the evidence has only recently been accepted by some of our leading physiographers, it is natural that as yet there should not be universal acceptance of so new an idea, carrying with it such tremendous consequences. But the fact that some workers have not yet accepted the doctrine does not necessarily constitute a strong argument against it, and certainly not enough to counterbalance the overwhelming evidence in its favor. When a large number of people are involved, ultraconservatism is always to be expected among some of them. There are, for example, even at the present day, some highly intelligent men who are writing

PSM V70 D119 Hidden glacier valley a tributary to the yakutat bay inlet.jpg

Fig. 13. The North Wall of Hidden Glacier Valley, a Tributary to the Yakutat Bay Inlet, the Glacier Terminus Showing in the Midground. Note the smoothed, striated lower walls due to glacial erosion as contrasted with the irregular topography of the higher slopes due to ordinary weathering and stream erosion. A hanging valley enter-at about the level between these two classes of slopes about a third of the way from the right margin above the glacier. Photograph by R. S. Tarr.