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Sierra Club Bulletin 



gineers had hinted at the idea, but only in an uncertain way. In 

 letters to the writer Gilbert considered that "all great engineers 

 had a sort of intuitive knowledge of the principle." 



In 1898 Gilbert accompanied the Harriman Expedition to 

 Alaska, and there he appreciated the action of glaciers in ex- 

 cavating the peculiar land forms known as fiords, sounds, 

 cwms (coombs), cirques, corries, overdeepened lake basins, 

 and U-shaped valleys in cross section. Although he had come 

 to this idea quite independently, nevertheless Henry Gannett 

 had already in 1898-1899 announced the principle, while W. 

 M. Davis and others had also appreciated the facts indepen- 

 dently, from a study of Norway, New Zealand, and other 

 places, between 1899 and 1902. 



Gilbert also made valuable contributions to the theory of 

 isostasy, first announced by C. E. Button — namely, that unit 

 cylinders of earth material, considered at right angles to the 

 earth's surface, whether in the high mountains or in the deep 

 oceanic areas, are approximately equal in weight down to a 

 depth which is approximately one hundred miles below the 

 earth's surface. 



But his greatest work is his ''Analysis of Land Sculpture," 

 in v/hich he gives a clear statement of the manner in which the 

 weather and the streams combine to carve the lands into the 

 shapes as we see them now, whether as fretted alpine peak, as 

 scarred volcanic pile, as deeply dissected plateau or rolling up- 

 land, as foothill slopes, or as coastal or inland plain of accu- 

 mulation. 



This is a masterpiece, a classic, like Hutton's work and 

 Playfair's ''Illustrations." It is only fair to state here that Hut- 

 ton and Play fair, about one hundred and twenty years ago, had 

 evolved a similar scheme. They lived before their time, and 

 their classics lay unheeded in libraries almost inaccessible to 

 workers. Gilbert rediscovered their principles and went be- 

 yond them. Later, upon learning of their work, his modesty 

 led him to award Hutton most of the credit. Naturally, Gil- 

 bert was a great admirer of Hutton, and could never under- 

 stand why the Englishmen had neglected their great com- 

 patriots. 



During recent years Gilbert had made a detailed and valuable 



