100 GEOVE KARL GILBERT— DAVIS [UEilol *\xoTxxi, 



WANDERING STREAMS ON PLANATION SURFACES 



Several other topics are treated so effectively and withal so pleasingly that they deserve 

 statement in brief form. "Planation" is explained as the result of lateral shifting by a stream 

 which has reduced its slope to so low a declivity that its capacity for transporting load is bal- 

 anced by the load it receives to be transported; it then swings from side to side, beveling off 

 the underlying strata whatever their attitude in a gently inclined plain; plains of this kind, 

 veneered with laccohthic gravels, being frequently seen around the Henry Mountains. An 

 explanation of the structure of flood plains is added which merits attention: In consequence 

 of the lateral shifting of a balanced stream, " every part of the valley which it has crossed in 

 its shiftings comes to be covered by a deposit which does not rise above the highest level of 

 the water. . . . The deposit is of nearly uniform depth, descending no lower than the bottom 

 of the water channel, and it rests upon a tolerably even surface of the rock or other material 

 which is corraded by the stream" (127). A corollary of this explanation gives correction to 

 an error earlier made by an eminent American geologist, who supposed that "river terraces 

 in general are the records of sedimentation, when in fact they record the stages of a progressive 

 corrasion. . . . There is a kindred error . . . involved in the assumption that the streams 

 which occupied the upper and broader flood-plains of a [terraced] valley were greater than 

 those which succeeded them. ... Of the same order is the mistake, occasionally made, of 

 ignoring the excavation which a stream has performed, and assuming that when the upper 

 terraces were made the valley was as open as at present, and the volume of flowing water was 

 great enough to fill it." A diagram is introduced showing Gilbert's own idea of valley-side 

 flights of terraces, each step being carpeted with a flood-plain deposit lying on an eroded sur- 

 face of the mass in which the cutting and depositing river excavated its terraced valley; and 

 here the comment is added: "The pre-existent material in the region of the Henry mountains 

 is always rock in situ, but in the Northern States it often includes glacial drift, modified or 

 unmodified" (132, 133). It surely required an unusual capacity for seeing and t hinkin g to 

 develop ideas so novel and so just as these. 



In connection with the wandering of streams down the radial slopes of their alluvial cones, 

 reference is made to Blake's early observations regardmg the effect of the Colorado delta in 

 cutting off the upper end of the Gulf of California, the severed end of the gulf having been later 

 evaporated to dryness so that its depressed floor now forms the Colorado desert. 



Its bottom, which is lower than the surface of the ocean, is strewn with the remains of the life its waters 

 sustained, and its beaches are patiently awaiting the cycle of change which is slowly but surely preparing to 

 restore to them their parent waters (135). 



This passage is quoted here in order to introduce an item of 15 years later date, predestined 

 by the intimacy that was formed between Gilbert and Powell in the Henry Mountains epoch. 

 In 1905 when the misbehaving Colorado River was turning part of its flood waters into the 

 depressed desert, as if striving to verify Gilbert's prediction, he confessed to a friend his share 

 in the authorship of an article, written in Washington in 1891 and published over Powell's 

 name, on a part of the desert known as the Salton Sink. The confession explains the circum- 

 stances of attending the composition of the article as follows: 



Powell sent for me one afternoon and said he had been asked to write on the Salton Sea; he had already 

 written twice and could not write again without repeating; he could not turn the invitation over to me because 

 the publishers wanted his name; if I would write he would share the spoils with me. I had my stenographer 

 come to my house and dictated the article that evening. [Let the reader note that survey time was not infringed 

 upon]. Powell added two paragraphs next morning and it went off before night. My share was fifty dollars, 

 which made me happy. I have just reread the article . . . and it seems to me to check up by modern history 

 remarkably well. Of course it is Powell's article, so far as any references in print are concerned — and I think 

 I wrote it with exceptional freedom because he instead of I was to be responsible. 



If any punctilious readers feel a bit scandalized by this performance of a man so irreproach- 

 able as Gilbert, let them remember the pious fraud perpetrated by the equally impeccable 

 William James. He was one evening attending to the illustrations of a lecture at Harvard on 

 a physiological subject by a visiting professor from Johns Hopkins; a lever touching the pulse 



