TOPOGRAPHIC FEATURES OF THE DESERT BASINS.- 590 
tion. Valleys dammed by alluvium, local depressions dried below 
their outlets, ponds like those of the Great Plains and coulées, as well 
developed as those of Washington, allabound. Many of these inclosed 
areas are of considerable salinity, but all are recent and most are tiny, 
and it does not seem necessary to discuss them in detail. In area 
they vary from ponds or playas that drain a few acres to the large but 
shallow basin of the plains of San Augustine in western New Mexico, 
compassing perhaps 1,500 square miles. This latter basin and the 
smaller ones in its vicinity probably once drained into the Rio Grande 
instead of the Colorado, but otherwise they do not differ from their 
western analogues. In the absence of full and detailed knowledge of 
the entire plateau region it is impossible to deny categorically the 
existence of basins, the size or antiquity of which would give them 
present interest. However, it seems very probable that, with one 
exception, no such exist. This exception will now be described. 
THE HUALPAI BASIN. 
Tn its southwestern portion the Colorado plateau has been more modified than else- 
where, both by movementand erosion, and here lies the Hualpai or Red Lake Valley, 
occupying a depression in the making of which both movement and erosion have had 
ahand. There is little doubt that'this valley once drained northward to the Colorado, 
but this drainage may have been a long time ago. The present divide, though allu- 
vial, is high and may be pre-Lahontan. The writer, while inclining to the opinion 
that it is, does not care to advance any conclusion. The area of the basin is 
approximately 1.450 square miles and its deepest depression contains a playa which 
is not known to be especially saline. 
THE PONDS AND COULEES! OF EASTERN WASHINGTON. 
The central and eastern part of Washington is largely a great lava 
plateau, somewhat warped and cracked by the movement which was 
more pronounced farther south and west, but preserving much of its 
original character. Being of little relief and in general of poorly devel- 
oped drainage, this plateau has suffered severely by desiccation and is 
now dotted with literally hundreds of small inclosed basins, due prima- 
rily to inequalities in the lava surface and.resembling in every way the 
small pans of the Christmas Lake, Abert and Alkali Valleys, as dis- 
cussed on pages 22 to 26. Some of these depressions now carry per- 
manent or intermittent lakes, most are slightly or moderately saline, 
but all are recent and owe their inclosed condition to the decay of the 
drainage system to which they once belonged. So far as known none 
drain an area of over a few square miles and none are important. 
Another and jess usual type of inclosed basin is represented by the 
“‘coulées,”’ or long, narrow valleys with steep walls and flat floors, the 
floors being dotted with lakes. Essentially these are old stream chan- 
nels, the history of which, stripped of all details, is as follows. When 
the lava plain was uplifted and warped, numerous cracks formed 
1 The word ‘‘coulée’’ is here used as locally understood. 
