176 
EOLIAN GEOLOGY 
result of basinal sand-drifting on the arid piedmont; the other is 
water moved, flowing down in storm-waters. The one is being 
continually augmented; the other only rarely as in times of the 
infrequent and sporadic rain-falls. Small wonder is it that on the 
margins of the intermontane basins the sand-plains so completely 
smother all traces of arroyo work as to all but obliterate the evi¬ 
dences of the existence of other deposits and that the single phe¬ 
nomenon should be so generally mistaken for another. 
Keyes. 
