240 GROVE KARL GILBERT— DAVIS [MEM " IRS [voL TI xxt 



date had been worn down to low relief before the existing ranges were heaved up; if that view 

 be correct, traces of the worn-down surface of the old mountains ought to be found on the back 

 slopes of the new ones; but no mention is made of such an old surface. Yet such worn-down 

 surfaces would be of importance in the discussion, for tbey would correct the idea that the 

 basin ranges result from "compound erosion" operating continuously on rocks that have been 

 continuously upheaved by "compound earth movements" since Jurassic time. If the worn- 

 down surfaces exist in the back slopes of the ranges, they would prove that earth movements 

 had been wanting during a considerable interval of time, and that erosion as well had almost 

 ceased in the latter part of that interval. Gilbert's omission of this significant element of the 

 argument was perhaps because he had, at the time of writing his report as censor, no personal 

 knowledge of any such surfaces. Fortunately, his notebooks of the summer of 1901 show 

 that he discovered a good number of them, and to his field studies of that year we may next 

 turn. 



THE SUMMER OF 1901 IN UTAH 



Gilbert fortunately secured authority to make "a review of the question of the mode of 

 origin of the mountain ranges and intervening valleys of the Great Basin region " in the summer 

 of 1901. W. D. Johnson accompanied him as topographer, as he had in the Bonneville studies, 

 in spite of the untoward incident of 1893 in Colorado, recounted above. Some extracts from 

 Gilbert's notebooks -of this season are presented below, from which it appears that the House 

 and Fish Spring Ranges in Utah were selected for special study; these being the same ranges 

 which 29 years before, as already told on an earlier page, were most definitely described in the 

 field notes of his first season as consisting of uplifted blocks, one with eastward tilt on the 

 eastern side of an inferred fault line, and the other, farther north, with westward tilt on the 

 western side of the same fine; and it was these ranges which then impressed him so vividly as 

 typical examples that, when he was at the bottom of the Colorado Canyon two months later, 

 he drew from memory an imagined bird's-eye view of them in a notebook diagram, here repro- 

 duced on page 56. 



The field season of 1901 seems to have been both successful and enjoyable, as it resulted 

 in the collection of a large body of valuable material, closely pertinent to the problem under 

 discussion; but this material was, most unhappily, never published on account of the disappoint- 

 ment caused by a calamity in the following spring. Before recounting that sad episode, a 

 few items may be quoted from Gilbert's letters of the summer; both include passages that 

 illustrate very well his quizzical way of putting things. The first was to one of his sons: 



This letter has been interrupted while the cook cut my hair, taking off all but about a quarter inch — and 

 making prominent some scars I got two days ago in trying to lift the roof of a cave. I was in the cave for shelter 

 from a rain storm when I heard the roar of a storm-torrent. It was two miles away, but I thought it close and 

 started to run and see the spectacle. Then I met the cave roof and stopped and sat down again. Fortunately 

 the damage was only skin deep. . . . We call this "Sunday" regardless of the calendar, because Johnson & I are 

 both staying in camp. 



The tumult of temporary torrents by which the silence of the desert is occasionally broken 

 is a characteristic of the arid region; another instance of the kind was recorded in one of Gil- 

 bert's notebooks for the same summer, when an hour after a storm at night the roar of the 

 flood was heard; the next morning a sheet of water covered the low-lying playa in the trough 

 of the intermont detrital plain. 



Later in the season a letter to a geological correspondent outlined the work in hand and 

 commented on some of the conclusions reached : 



I have not been outside of Utah and am now homeward bound. I began with a study of the physiographic 

 expression of faults in the Wasatch and continued it in the Oquirrh; and the chief thing I have done since is to 

 work out the structure of the House range. What was long ago suspected is now proved, that certain triangular 

 faces of the Wasatch, between canyons, are remnants of an inclined fault plane. They retain slickensides and 

 slabs of indurated shear-zone. On the Oquirrh they are followed below ground by mines, the hanging wall 

 being wash. . . . Among my interesting finds are a number of mistakes made by Gilbert, one of the Wheeler 

 geologists, in 1872; but he was substantially on the right track as regards Basin range structure. 



