36 University Geological Survey of Kansas. 
Cottonwood river valley. The north and south divides between 
the creeks have a gradual northward slope of about twenty feet 
to the mile, and their sides along the creeks are deeply indented 
by erosion. ‘They vary in hight above the water level in the 
streams from 100 to 150 feet. ! 
The area is a dissected plateau forming a very irregular sur- 
face near the divide, where it is more more or less protected by 
the Dakota sandstone. Toward the north where the Dakota is 
absent the topography is much smoother, and the surface slopes 
gradually to the Smoky Hill river. 
The land in the northern part of this central area has about 
the same elevation as the northern gypsum area and the to- 
pography is quite similar. It shows a more advanced stage of 
erosion, for the remnants of the plateau in the form of divides 
are narrow, and the river and creek valleys are broader. The 
Smoky Hill river in its wide chanel has a very winding course, 
and is depositing material rather than eroding. It has cut its 
way down almost to the level of the larger river of which it is 
in reality a tributary. It has then nearly reached a base level 
with reference to the larger river, but it is still far above the 
true base level which is sea level. 
In the southern part of the area, however, the land is higher 
and is protected by the harder rock, so that the topography is 
much rougher than in the other portion of the same area, or in 
the northern area. The streams have a greater fall and so a 
greater velocity, and erode more rapidly, while the hard sand- 
stone protects the divides and they are cut into hills with steep 
slopes. Hrosion as yet has not advanced as far in this portion 
of the central area as other parts. We can readily imagine that 
the cap of Dakota sandstone extended over at least a part of the 
northern portion of this area and now has been removed by 
erosion, though this does not at the present time admit of proof, 
as all traces of the sandstone there are lost. 
A number of small towns are situated along the Missouri 
Pacific and Atchison, Topeka & Santa Fe railroads in the cen- 
tral part of the area, while larger cities lie along the river. The 
plaster manufacture is the main industry of this part of the 
