ac's? 1 * of sconces] POWELL'S SURVEY 77 



Mountains sketches, Figures 34, 39, 42, 48, 49, were redrawn in ink from Gilbert's originals by 

 "F. S. D." (Dellenbaugh), who had been with Powell on the Colorado in 1871 and with Thomp- 

 son in the Henry Mountains in 1872; a special red ink had to be used and the lines kept very 

 thin for reproduction by a "photographic process" new at that time. Other sketches, Figures 

 16, 27, 36, 43, 44, were more conventionally worked up as woodcuts in artisanlike fashion, 

 with little appreciation of western scenery. Both styles of "copies" depart undesirably far 

 from the originals; the woodcuts in particular, overloaded with monotonously uniform lines, 

 give the impression of dark landscapes under a cloud-covered sky, altogether inappropriate for 

 the arid plateau country. A few halftones, here reproduced from Gilbert's originals, show 

 that very little "working up" was needed, for rough as his drawings were, every touch by 

 which the original is "improved" by some one else than the observer himself is likely to intro- 

 duce departures from nature. Special mention should be made of the frontispiece to the report, 

 a block diagram in two sections, like the one prepared by Gilbert for Powell's Uinta Mountain 

 report above noted; it shows Mount Ellsworth in the foreground, and a stereogram of its 

 restored dome in the background, with indication of the strata involved on the right side of the 

 block; this was evidently Gilbert's design, although it was drawn by some one else. 



Besides these pictorial views, the report includes two full-page photoplates of models and 

 two of stereograms, which are of great value to the reader in aiding him to visualize the region 

 treated. Their value in this respect was appreciated by able scholars in France, as Gilbert 

 had the pleasure of knowing when he visited Paris in 1888. One of the models, reproduced on 

 a scale of about 9 miles to an inch, represents an area of 76 by 80 miles, extending from the 

 high plateaus on the west to the Colorado on the east, with the long Water-pocket flexure 

 through the middle and the Henry Mountains between it and the river; this is based on "Topog- 

 raphy by W. H. Graves," but as already noted Gilbert himself did much topographic field 

 work in the way of plane-table surveys and barometer readings. The maker of this model is 

 not named, but it is believed that Gilbert had much to do with it. The other model, repro- 

 duced on a scale of a little more than 4 miles to an inch, represents the Henry Mountains alone, 

 and was made "by G. K. Gilbert" ; this is repeated in another page plate with geological colors 

 added. The stereograms, which appear to have been built up from the models, represent the 

 deformed surface of a single geological stratum for the same two areas. Gilbert undoubtedly 

 had help in the laborious construction of the originals, but even so, it is difficult to understand 

 how they could have been designed and completed in the same four months that were occupied 

 with the writing of the report. 



The rapidity with which this famous report was prepared and the keen analysis of the 

 problems that it treated point to a fundamental change of conditions in Gilbert's scientific 

 life, caused by his transfer from the Wheeler to the Powell survey. He rose immediately to 

 the occasion; and it is characteristic of his conscientious nature that the satisfaction he felt 

 in the great opportunity opened to liim by Powell took the form of gratefully recognizing its 

 advantages and loyally accepting full responsibility for making the most of them. The pref- 

 ace to his report reads: 



If these pages fail to give a correct account of the structure of the Henry Mountains the fault is mine and 

 I have no excuse. In all the earlier exploration of the Rocky Mountain Region, as well as in much of the more 

 recent surveys, the geologist has merely accompanied the geographer and has had no voice in the determination 

 of either the route or the rate of travel. When the structure of a mountain was in doubt he was rarely able 

 to visit the points which should resolve the doubt, but was compelled to turn regretfully away. Not so in the 

 survey of the Henry Mountains. Geological exploration had shown that they were well disposed for examina- 

 tion, and that they promised to give the key to a type of structure which was at best obscurely known; and I 

 was sent by Professor Powell to make a study of them, without restriction as to my order or method. I was 

 limited only in time, the snow stopping my work two months after it was begun. Two months would be far 

 too short a period in which to survey a thousand square miles in Pennsylvania or Illinois, but among the Colo- 

 rado Plateaus it proved sufficient. A few comprehensive views from mountain tops gave the general distribu- 

 tion of the formations, and the remainder of the time was spent in the examination of the localities which best 

 displayed the peculiar features of the structure. So thorough was the display and so satisfactory the examina- 

 tion, that in preparing my report I have felt less than ever before the desire to revisit the field and prove my 

 conclusions by more extended observation. 



