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Sierra Club Bulletin 



possessed a keen, exact, and philosophical mind, which showed 

 through his speech and writings. He delighted to extract new 

 principles from masses of observed facts, and these mental 

 quaUties, combined with a love of nature, determined the Hnes 

 of his life-work. Into this he grew as opportunity offered 

 through the Ward Natural Science EstabUshment, the Ohio 

 Geological Survey, the Wheeler and Powell explorations of 

 the west, and finally the United States Geological Survey. He 

 was the only man who, during the existence, through the past 

 thirty years, of the Geological Society of America, has been 

 elected a second time its president, a recognition of his char- 

 acter as much as of his ability. Speaking in acknowledgment 

 of this unusual honor, he said that he was fortunate in being 

 able to pursue a life-work which had always been to him a 

 source of delight. 



Gilbert entered geology at a time when it was mostly a de- 

 scriptive and qualitative science. The habit of his mind was 

 logical and mathematical. These were the qualities of which 

 geology at that time stood in need, and his ability in these di- 

 rections, even to the close of his life, is shown in his mono- 

 graphic studies on the ''Transportation of Debris by Running 

 Water," prosecuted during years of ill-health, and published 

 when he was seventy-one years old. That the same quahties 

 were present even in his boyhood may be gathered from the 

 following extract from one of his letters to the writer, in which 

 he was discussing the possibility of the rhythmic action of the 

 tides producing a progressive motion : 



When I was a boy I noticed that by rocking a skiff I gave it a for- 

 ward motion. That led to the trial of other impulses, and I found that 

 by standing near the stern and alternately bending and straightening my 

 legs, so as to make the skiff rock endwise, I could produce a forward 

 velocity of several yards a minute. If I stood one side of the medial 

 line, the skiff moved in a curve. The motions I caused directly were 

 strictly reciprocal, the departures from initial position being equaled by the 

 returns. The indirect result of translation was connected with reactions 

 between the water and the oblique surfaces of the boat. There seems to 

 me a close analogy between these reactions and theoretic reactions of an 

 ocean swayed by tidal forces upon oblique surfaces of its basin. 



He will be longest remembered for his classic papers on the 

 Henry Mountains and on Lake Bonneville, but his deep-seated 



