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GEOLOGICAL CRITICISM 317 
link in explanation of the topographic development of the arid region. 
My difficulty always arose in explaining what had become of the material 
removed from the one-time plateau now reduced to a few remnantal 
sierras, save on the hypothesis of filled-up canyons in the axes of the 
valleys, but Keyes satisfactorily explains the disposal of the debris through 
deflation. In general, too, his mental picture of the intermont rock-floors 
forming the greater part of the region in question and of the sharp rise- 
of the rugged sierras from these floors is signally just — in which, by the 
way, he differs widely from Tolman (whom he quotes), whose illustrative 
sections reveal hypotheses having practically nothing to do with the facts 
of the region as known to Keyes and some others no less than myself; 
indeed when I had the satisfaction of meeting Tolman and pointing out to 
him that his great ideal aprons of colluvial material were really so tenuous 
as to be worn entirely through in the three-inch deep path leading up to 
the Tucson Desert Laboratory, he was entirely at a loss, and could only 
think of this as an exceptional case instead of the general one for the 
entire region. Now I have no doubt that Doctor Keyes will take in good 
part the foregoing remarks which, if critical, are constructively so rather 
than destructive; and that in the light of my experiences in the region 
which he describes, as set forth herein, he will be able to so modify his 
expressions so as not to lay himself open to less tolerant and friendly utter¬ 
ances by others. I do not specify passages in detail; for the important 
thing is for him to get the spirit of what I have said and apply it to each 
passage as he re-reads the manuscript — for, as you see, I think it should 
go back to him in the light of suggestions herein. 
To my mind the use of the term “deflation” is questionable. It is quite 
true that it has been extensively used, having been put in current circula¬ 
tion in this country by Johannes Walther (first in a publication which I 
happened to edit), yet none the less it is so bad philologically and the 
same term is so clearly fixed in its philologically correct meaning that it 
really ought to be permitted to drop quietly into innocuous desuetude. I 
feel confident that if this point were put up to the author he would ac¬ 
quiesce in the judgment as to the unsuitability of the term. 
Again, I am forcibly struck with a certain dearth of bibliographic 
reference. Of course, I realize that when the paper was first prepared 
it must have been designed rather as a preliminary announcement or a 
caveat on the field it covers, and that as the matter has grown in the 
author’s hands he has somewhat modified the treatment without changing 
his viewpoint to what it would be were he to take the matter up anew 
to-day. In my judgment Doctor Keyes would find himself materially 
fortified in his position, and at the same time be able to increase materially 
the effectiveness of the presentation by some marshaling of current au¬ 
thority; and I do not think he would lose anything on the score of credit 
for originality. The bibliography of the subject is now in excellent condi¬ 
tion, thanks^ to the work of Mr. Free, and it would be quite easy for 
Doctor Keyes to obtain any needed access to this material. 
