HAwortu. | The McPherson Equus Beds. 289 
niore at McPherson and contains an abundance of water, as it does 
wherever it is found. The upper part of the gravel stratum grades 
into a stratum many feet in thickness, which is partly argillaceous 
and partly arenaceous, sometimes containing isolated sand beds, or 
at least sand beds of great irregularity, and which contain very 
little water. The upper surface of this stratum is nearly on a level 
with the rim of the deeper channel (See sections referred to above). 
Over this and also extending over a very slightly undulating Per- 
mian floor for fifteen miles to the east is a stratum of sand varying 
‘in thickness from 30 feet (at McPherson, according to Prof. S. Z. 
Sharp) to 3 feet in other places farther east, but averaging 6 or 8 
feet in thickness. This stratum also contains a good supply of 
water. It covers nearly the entire area of the Equus beds except per- 
haps a portion to the north. The uppermost stratum is composed of 
clay varying in color and texture. It covers the entire area and is 
from 10 to 35 feet in thickness. Within this clay layer in the 
northern part of McPherson county is a stratum of volcanic ash from 
18 to 24 inches thick. | 
Nodules of calcium carbonate are frequently found in both the 
upper and lower stratum of clay. Asa rule they are very irregular 
in form, but generally show a slight roundness of form. Some of 
these are quite hard, while others are very soft, as is the case at the 
McPherson sand pit on the Boggs farm two miles southeast of the 
city, where it is 20 inches thick in places. A specimen of this was 
submitted to Dr. G. P. Grimsley, who states that it is “one mass of 
small prismatic crystals with pyramidal terminations, with strong 
double refraction and no cleavage. ‘They effervesce with acids and 
are crystals’ of aragonite (CaCO,), the orthorhombic form of cal- 
cium carbonate.” No structure could be determined in the hard 
nodules. Doctor Grimsley pronounces the voleanic ash as “glass 
grains or flakes, fine and angular, some of which are feebly doubly 
refracting.” A specimen of the sand was examined by him and 
found to be “rounded quartz grains with a number of angular ones.” 
Specimens of Dakota sandstone and sand from Dakota sandhills 
were also pronounced of the same character, except differing in 
fineness. As no feldspar grains were found in the sand it would 
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