208 University of Kansas Geological Survey. 
toward the southern. They are highly ferruginous in character, 
and curiously shaped ferruginous nodules are of common occurrence. 
They vary in texture from the loosely cemented sand to the very 
coherent sandstone. 
The Dakota sandstone is used for building purposes to only a 
limited extent. Representing approximately both extremes in the 
scale of hardness, they are either too hard to be dressed or too soft 
to withstand weathering. Another objection urged against their 
use as building stone is that of their color. Owing to the constantly 
varying amount in the quantity of iron oxide in the stones of the 
same quarry even, many shades of color exist. 
Many peculiar effects of erosion are to be seen in the sandstone 
area. Standing on the hillside a few miles east of Ames, in Cloud 
county, is a single escarpment which has weathered into a form 
resembling an ancient castle. At Pawnee Rock, in Barton county, 
a similar outcrop stands sentinel over the Arkansas valley. Both owe 
their preservation to a protecting covering of the Benton limestone. 
The natural fortifications of Pete creek, in Washington county, are 
only equaled by those at Fort Riley. Soldier Cap Mound, in Saline 
county rises 140 feet above the surrounding country and consists of a 
single point of shales protected by a layer of sandstone. See Plate 
XXIV. The Smoky Hill Buttes are similar mounds in the south- 
western part of Saline county, Plates V and VI. At Rock City, in 
Ottawa county, the sandstones have been eroded into peculiar 
rounded forms, resembling glacial boulders. ‘The intersecting chan- 
nels, with their inclosed forms, give to the group the appearance of a 
city, hence the name. With the exception of the spherical forms, 
similar groups occur in Lincoln, Ellsworth and Russell counties. In 
the majority of instances, the white sandstone rests upon the red; 
but in a number of instances they occur in the same horizon. East 
of Bavaria both were found in the same horizon, the one color passing 
gradually to the other. 
THE UPPER GROUP. 
lignite Horizon.—Resting upon the gray or white sandstone, in 
the last upper layer of the sandstone group, is a thin bed of lignite 
which is entirely wanting in certain localities. The lignite varies in 
