288 GROVE KARL GILBERT-DAVIS tME * 0IES [$ES 



processes. The conclusions reached as to such structures have been -widely accepted; Gilbert's 

 name is more closely associated with laccoliths than with any other one class of geological 

 phenomena; but his views as to the essential processes of laccolithic intrusion have rarely been 

 appreciated. On the other hand, his remarkable analytical discussion in the third chapter of 

 the same report which treats the principles of land sculpture on the basis of observation and 

 reflection during five years of western exploration, has long enjoyed the high appreciation it 

 so fully merits. As to the last three years on the Powell survey, they were not particularly 

 fruitful, except in so far as they happened to give occasion for the study of Bonneville shore 

 lines. The work then done on land classification and the possibilities of irrigation in Utah may 

 be regarded as the nearest approach that Gilbert ever made to economic geology; and that 

 work represented his interest much less than Powell's. 



THE NATIONAL SURVEY: BONNEVILLE AND WASHINGTON 



On the formation of the national survey, Gilbert again found opportunity widely opened 

 in the study of Lake Bonneville under King, an investigation wholly to his liking, inasmuch as 

 it was concerned essentially with physical geology and physiography; and then for a period of 

 several years he had the aid of a small corps of assistants with headquarters at Salt Lake City. 

 Plans made at the time show that he looked forward to a long-continued study of a large region, 

 but his hopes in that direction were disappointed when, after only two years in the Great Basin, 

 he was transferred to Washington, where for 11 years thereafter he was greatly distracted from 

 the scientific tasks of his preference. His famous Bonneville monograph, slowly brought to a 

 conclusion after many interruptions, was foreshadowed by partial statements in two annual 

 reports of the director and anticipated by Russell's monograph on Lahontan, in the composition 

 of which, however, Gilbert had an influential hand. When the Bonneville volume finally 

 appeared it at once became a classic, and it still remains the most serious study of a large arid 

 continental basin anywhere in the world. Apart from a few chemical analyses of lake sedi- 

 ments, a few experiments on sedimentation, and a short paleontological study, all conducted 

 for Gilbert by others, this matured discussion is another example of Gilbert's preference for 

 investigations that involve only keen field observation and critical mental interpretation. 



The geological mapping of the Appalachians was in Gilbert's charge for a time at Washing- 

 ton, and appears to have been conducted on a plan that at least had his approval if it were not 

 his invention; but the conventional subjects of stratigraphy and structure seem never to have 

 absorbed his attention. The one Appalachian problem that did attract him was a novel one, 

 namely, the physiographic interpretation of successive cycles of uplift and erosion on the basis 

 of principles that he had come to understand in the West; but he was so occupied with duties 

 of organization, consultation, administration, and supervision in the Washington office that 

 this problem was largely solved by others before he reached it. The original work that he under- 

 took during this decade of uncongenial indoor duties concerned the physiographic interpretation 

 of Pleistocene lake shore lines in northern Ohio and western New York, and was accomplished 

 chiefly in summer vacations; it may be regarded as an extension of his earlier study of the 

 Maumee Valley in the light of his Bonneville experience. As he was at once engrossed with 

 many other subjects when he returned to Washington, most of his observations were never 

 reported in the detail that they deserved, and such brief articles as summarized them were 

 published in unofficial form elsewhere than in survey volumes. But when the interpretation of 

 lake shore lines led him to study the evolution of Niagara Falls, his most significant conclusions 

 on that grand subject, which became peculiarly his own, were repeatedly presented in popular 

 scientific lectures to delighted audiences; and even if the items of fact were concisely stated, 

 such was not the case with the argumentation to which the facts led: that was searchingly 

 elaborated. It may be here recalled that two essays of apparently paleontological nature — the 

 "Age of the Equus fauna," a chapter in the Bonneville monograph, and the "Age of the Poto- 

 mac formation," published apart in 1896, are both in reality concerned for the most part with 

 physiograpluc questions. 



