acadkmt of sconces] WHEELER SURVEY 63 



Just why Powell's contribution to the basin-range problem was not quoted, and why 

 Dutton alone was credited with the two-cycle origin of the ranges is not clear; nor is it immedi- 

 ately manifest why Gilbert himself took no public part in the discussion which was for a time 

 actively prosecuted among the geologists of the several governmental surveys in Washington. 

 It is impossible to believe that he was not interested in the discussion, and that he was not 

 personally acquainted with Powell's and Button's views before they were published; for the 

 three men were closely associated during the very years when the discussion was at its height. 

 Indeed, in spite of Gilbert's making no claim in his posthumous essay to any share of the new 

 ideas which he there credited to King and Dutton, it is eminently possible that he had had a 

 significant share in developing them, but that having had his own say in his report he left the 

 announcement of the new ideas to his seniors. Such an interpretation of the case is much 

 more consistent with the activity of his intellect and the generosity of his character than the 

 supposition that he had dismissed the problem from his mind, or to imagine that, while carrying 

 it in his mind, he made no contribution to it. Moreover, his silence was consistent with his 

 known dislike of controversial discussions. For many years the basin ranges were mentioned 

 in his reports only incidentally, when they were needed to make a setting for some other problem. 

 For example, in a discussion, to be mentioned again in a later section, of the " origin of jointed 

 structures " with especial relation to the jointing of the Bonneville clays, it was briefly announced 

 that although there is evidence of post-Quaternary displacements in the region, the "movements 

 were small and vertical, and the type of structure exhibited by all the surrounding mountains 

 is one implying vertical displacement and no lateral compression." 5 Such a statement merely 

 repeated what had been said before, without developing a new point of view. 



GILBERT ON THE ORIGIN OF THE SIERRA NEVADA 



Fortunately, however, there is a brief statement published in 1S83 concerning the origin of 

 the Sierra Nevada, which makes it clear that Gilbert had then become aware of the two-cycle 

 development of that mountain range, and from this it may be fairly inferred that he had at the 

 same time come to recognize the probability of a two-cycle development for the basin ranges 

 also. This statement is to be found in a review 6 which he wrote of Whitney's " Climatic 

 changes of later geological times," and to which further reference will be made in a later section. 

 Whitney, following the geological philosophy generally accepted in his day, had assumed that 

 the Sierras had been uplifted once for all in Middle Mesozoic time, and that their present relief 

 represents simply the unconsumed residuum of the primitive uplift; Gilbert, on the other hand, 

 interpreted the present Sierras as exhibiting the work of revived erosion following renewed 

 uplift after the more or less complete degradation of their Mesozoic predecessors. He saw 

 that the Sierran highland is an inclined plain; "its plateau character is not given by a contin- 

 uous stratum of hard rock parallel to the general surface, but has been produced by the uniform 

 erosion of a system of plicated strata. Such uniform erosion could only have been produced by 

 streams flowing at a low angle"; and since the time when they flowed in that manner, the 

 mountain mass has been uplifted with a slant to the west. The recency of the uplift is shown 

 by its incompleteness, as attested by recent earthquake-making displacements along its eastern 

 base. The same subject appears to have been further discussed under the title, "Stages of 

 geologic history of the Sierra Nevada," before the Philosophical Society of Washington in 1887, 

 but no adequate record of that communication is preserved. 



INCOMPLETE STATEMENT OF THE BASIN-RANGE THEORY 



The deficiency of explanatory exposition in Gilbert's early accounts of the basin-range 

 faults is not easy to understand, unless it may be accounted for by the difficulty that is always 

 attendant upon completely thinking out all the elements involved in a new theory, and the 

 associated difficulty of writing them all down in precise phrases. As to the difficulty of pre- 

 cisely writing down his ideas, no one who is familiar with Gilbert's later reports would imagine 



8 Amer. Journ. Sci., Miv, 1S82, 50-53. 



8 Science, i, 18S3, 141-142, 169-173, 192-195. 



