194 GROVE KARL GILBERT— DAVIS 



successive volumes of proceedings do not contain his name, although they make frequent refer- 

 ences to " Gilberti" as attached to new species of plants and animals described by his admirers. 



After his famous Niagara lecture at the Toronto meeting of the American Association for 

 the Advancement of Science in 1889, Gilbert's contributions to its gatherings were of minor 

 importance for several years; but when the association met again at Buffalo in 1896, 10 years 

 after he had presented his first essay there on the age of Niagara, he reported upon new studies 

 of that river, as well as on the temporary "Algonquin River," by which the upper lakes were 

 for a time drained eastward across the Province of Ontario without passing through Lake Erie; 

 and the following year, at Detroit, he discussed "Earth movements in the Great Lakes region;" 

 both these contributions are elsewhere summarized. In the autumn of 1899 the death of 

 Edward Orton, who had been elected to the presidency of the association the previous summer, 

 left that office vacant; Gilbert was chosen to fill it and was thus given one of the highest marks of 

 scientific approval that an American scientist can receive. He presided at the meeting in 

 New York in 1900 and there read an address on "Rhythm and geological time," which proved 

 so acceptable that it was printed in full in three independent publications, 11 an honor rarely 

 accorded to any similar essay, and the more remarkable since no definite or striking results 

 were announced in it. The treatment of the subject was suggestive rather than conclusive; 

 its presentation was, however, developed in a highly characteristic manner, beginning with 

 simple and familiar examples of short-period rhythms, and ending with the precession of the 

 equinoxes. The leading suggestion was that apparently periodic alternations of sedimentary 

 deposits, such as he had seen in Colorado eight years before and had briefly described before 

 the Philosophical Society of Washington and the Geological Society of America in 1894, may 

 be due to some long-period rhythm in the physical processes that control erosion and deposition; 

 and inasmuch as recorded descriptions of stratified deposits do not suffice to detect the possible 

 consequences of such rhythms, he urged an outdoor "search for records of the ticks of the 

 precessional clock." 



Gilbert's pronounced liking for the mathematical treatment of problems may be perceived 

 in a number of his papers, especially in his account of the moon's face, already analyzed, and 

 in his several discussions of isostacy, to be described later. Still another illustration of the 

 same mental habit is indicated in one of his reports to Powell, dated March 12, 1894: "I have 

 been occupied largely during the month with the continued consideration of a plan for a machine 

 to solve problems in least squares," apparently in connection with the adjustment of observa- 

 tions in topographic triangulation; but nothing seems to have come of this effort. 



« Proc. A. A. A. S., xlix, 1900, 1-19; Science, xi, 1900, 1001-1012; Pop. Sci. Monthly, Iviii, 1900, 339-353. 



