286 GROVE KARL GILBERT— DAVIS tMEM0,M [&*™x£ 



lameness on the part of the would-be follower. The same next-to-last report is the only one 

 that was based essentially on experimental data ; it was indeed as much a study of an encnneerino' 

 as of a geological problem — the transportation of detritus by running water. His many other 

 papers are remarkably free from technicalities; their facts are directly and accurately stated, 

 their discussions are simply, clearly, and convincingly presented. The impression that they 

 create is one of calm reasonableness. 



His first independent investigation, a voluntary and very original study of the age of the 

 Mohawk gorge at Cohoes, near Albany, was exceptional in showing at once keenness in oberva- 

 tion and skill in interpretation; although the discussion was of narrowly limited range, it was as 

 strikingly quantitative as his final great study, made nearly half a century later, on the distri- 

 bution of hydraulic-mining debris in California. His work on the physiography of the Maumee 

 Valley in northwestern Ohio, one of his earliest studies as a member of a geological survey, was 

 marked by the delicate application of simple principles in the explanation of a landscape of 

 almost imperceptible relief; his originality was here shown in the announcement of the then 

 novel idea that, in view of the unevenness of the land surface over which the Pleistocene ice 

 sheet advanced, its margin must have been multilobate; an idea so rational that everyone on 

 learning it must have wondered why it had not been hit upon sooner; indeed, why he had not 

 hit upon it himself. 



THE WHEELER SURVEY REPORTS 



The two Wheeler survey reports on Gilbert's first three field seasons in what was then the 

 Far West are of uneven quality, and in this they reflect the hurried observations in certain 

 districts in contrast to the more gradual progress in others; but they reflect also a personal 

 dissatisfaction with the conduct of scientific investigation under military control, whether this 

 required the carrying of a carbine which he was glad to lose when his boat upset in the Colorado 

 River, or the postponement of publication which he wished to make promptly on return to 

 Washington. Yet although trammeled by these regulations, he was not trammeled by certain 

 premature geological generalizations of eastern teaching; for he saw that the almost unbroken 

 continuity of deposition from Cambrian to early Tertiary in the West gave direct contradiction 

 to the generally accepted view that the post- Carboniferous revolution of Em-ope and of eastern 

 North America had a world-wide extension ; and more important still he saw that the areas of 

 ancient crystalline rocks, both East and West, had not emerged from the sea to form the first 

 land surfaces around which the deposition of Paleozoic strata began, as was ordinarily taught 

 in colleges in the '70s, but that they represented long enduring and greatly degraded land sur- 

 faces of very ancient date, which on finally sinking beneath ocean level provided a sea floor on 

 which Paleozoic strata began their deposition. Thus rationally guided, Gilbert gained from 

 these three years in the West not only a wide acquaintance with the physical features of the 

 Great Basin, but also a broad understanding of the structure, the physical history and the 

 surface forms of the plateau province; and he gave an excellent account of that province as a 

 field for geological study, although it is to Powell that credit is properly given for the earlier 

 and fuller exploration of that wonderful region. On the whole it was experience rather 

 than publicity that Gilbert gained on the Wheeler survey. 



His work on the basin ranges is, however, an exception to the last statement, for the 

 theory of their origin as fault-block mountains is widely associated with his name. Yet an 

 adverse fatality seems to have attended all his relations to this fine problem. His first contri- 

 bution to it, a novel but incomplete conception, was chiefly to the effect that, notwithstanding 

 all the evidence found elsewhere for the uplift of mountains by lateral compression and folding, 

 the basin ranges are best explained as individual vertical uplifts Avith little compression. Two 

 additional elements of the theory were soon introduced by others; the occurrence of two periods 

 of deformation, one marked by compressional folding, the other by disruptive faulting, was 

 first suggested by King; and the occurrence of a long period of erosion between the two periods 

 of deformation, as proved by the peneplanation of the earlier mountains of compression and 

 folding before the uplift of the later mountains by faulting with little compression, appears to 



