ADAMS: A GEOLOGICAL RECONNOISANCE. 123 
other cases from the base of the sand hills or breaking from the 
Pleistocene. This is interesting when taken in connection with the 
fact that the water of the streams is nearly all brackish or saltish, 
and upon evaporation will leave behind a white efflorescence upon 
the vegetation or the dry bed of the stream. In the eastern por- 
tion of Woods county, just south of the Salt Fork, is situated the 
Salt Plain, which, with the encrustation upon the sand and salt 
grass, shimmers like a lake when seen in the sun. This Salt Plain 
has been considered by F. W. Cragin (Colorado College Studies, 
Vol. VI,) as being derived from the salt deposit of the lower por- 
tion of the Red Beds, as above described. Further west, in the 
vicinity of the gypsum horizon, the water in the creeks is bitter 
and often unusable for either man or beast, but wherever the sand 
hills or the Pleistocene deposits are sufficiently extensive sweet 
water is found in shallow wells or bursts forth in springs. On the 
south slope of the divide there are large areas covered with sand 
hills which are mostly extinct and bear a growth of blackjack 
timber. Along the north side of the Cimarron there is a belt 
several miles wide which is of this nature, but the sand hills are 
more active and the timber is absent or is replaced by cottonwood 
trees. Some of the hills reach a surprising height. Tall cotton- 
wood trees are found growing upon them, and the shifting of the 
sand has occasionally buried the trees so that only the top branches 
are seen protruding in sand pits in the top of the hills. A ridge of 
sand hills near the mouth of Eagle Chief creek is fully 150 feet 
high. North of the Salt Fork, in the northeast part of Woods 
county, is a similar ridge. 
South of the Cimarron river, in Woods county, the Glass moun- 
tains are marked on most maps of Oklahoma. A trip to this locality 
revealed the inaccuracy of the name. There is a bold escarpment 
with occasional isolated mounds, extending along the river and 
around the heads of the short creeks which are tributary to the 
river from the south. One of these mounds or buttes, perhaps the 
most prominent one, is situated at about the place at which the 
mountains are indicated on the map. From this place the escarp- 
ment is seen trending to the south and east away from the river, 
gradually becoming less prominent. Westward are many headlands 
and buttes which follow the course of the river. The protecting 
element in this escarpment isa ledge of gypsum twelve feet in 
thickness where I measured it. It is seen capping the butte in the 
illustration Plate XII. Below it are the readily yielding clays 
and soft shales of the Salt Fork formation. The butte here pictured 
