ILAIKIS, IBVA SIONS) (CURIB ZA IIBIO) IS NE WINDY IGINIOPSI (COUN 49 
is exceptionally scanty unless it is coated by an overwash of 
other material. This relation suggests that the condition essen- 
tial to the initiation of the excavation is the absence of vegeta- 
tion. The function of vegetation as a defender of the soil against 
ravages of the wind is already familiar, and it’ is easy to under- 
stand that whenever a tract of land in an arid region is deprived 
by some accident of its vegetal covering, the wind may at once 
become an important factor in its sculpture, clearing away all 
disintegrated material and, if the tract is small, producing a hol- 
low. If the hollow is so related to the slopes and drainage that 
it can gather water but will not be filled to overflowing, a perma- 
nent basin may result, for alternate flooding and drying will tend 
to keep the bottom of the hollow barren so that whenever it is dry 
the wind can continue its work. I believe the lake basins in ques- 
tion to have been created in this way. 
In their present condition it is evident that they are naturally 
subjected to antagonistic processes dependent on the wind. 
While they contain water they receive dust from every gale that 
sweeps across the country, and the sediment thus accumulated, 
which is of no inconsiderable amount, tends, of course, to fill and 
thus obliterate them. When they are dry the wind resumes its 
erosive action and their bottoms are degraded. Professor Cham- 
berlin has suggested an organic agency which also must consti- 
tute an important factor. Inaregion where springs and streams 
are rare the lakes are much resorted to by herds which, wading 
into the water to drink, carry away a coating of mud upon their 
feet and legs. The greater part of this mud is lost before they 
return, so that in this accidental way the beds of the lakes are 
steadily excavated and their margins enlarged. Horses and cat- 
tle sometimes increase their load by lying down in the mud, and 
their predecessor, the buffalo, is said to have the same habit. 
With the pools called buffalo wallows I have little personal 
acquaintance, and I am not prepared to say whether their basins 
are initiated by the wind, or constitute an independent class with 
purely bovine origin. G. K. GILBERT. 
