x 

is not available for agriculture. A few 
970 The American Naturalist. [November, 
Here and there in this area we find a bit of what might be termed 
tableland or a small scale. The upper surface is covered with a 
scanty vegetation of buffalo grass, cacti, sage-brush, and Agave 
angustifolia, with the ever-present loco weeds. But the slopes of 
the tableland are abrupt, and not a bit of green can be found on 
them. The geological history of the region can be predicted. 
This erosion will go on until the ridges are all worn away, and 
the bad lands again become reduced to a plain. Then as Hat 
Creek wears a deeper channel, erosion will again be increased, and 
the Bad Lands will be repeated. 
At first sight we all thought that the erosion was extremely 
rapid. The rock looks at first sight as if it would melt like 
sugar when it rained, but apparently this is not the case. My 
conclusions are that the winter frosts are the really efficient agents 
in the process. Rain and melting snow penetrate for an inch or 
two into the rock, and then the expansion of the freezing water 
disintegrates the outer surface of the rock, and it is only this 
outer portion which is soft. We found a place where for two 
years an irrigating ditch had emptied itself into the Bad Lands. 
It had nearly washed away this outer softened layer. The solid 
rock showed no signs of wear. 
In studying erosion in this region one must remember that 
here the rainfall is not excessive. Some ten or fifteen years ago 
Prof. Samuel Aughey published some charts and tables, the object 
of which was to show that the rainfall was increasing rapidly in 
‘Nebraska. The lines on his maps were as firmly drawn as the 
contour lines in a topographical survey. But alas! there is no 
evidence, nor has there ever been, to support these charts and 
these conclusions drawn from them. The annual rainfall is given 
or regions and times when there were no observations and no one 
there to observe. To-day our statistics are scanty, and now reach 
back far enough to enable us to say whether the annual rainfall is 
increasing at all. Apparently from the slight data we have in the 
Bad Land region a rainfall of sixteen inches in a year is unusual. 
With that slight amount extensive erosion is not probable. . 
The question is asked, Will these Bad Lands ever be of value? 
Not in the immediate future. A country so extremely irregular 
years ago this whole 
a 


