TWENTY-NINTH ANNUAL MEETING. 105 
places where one may travel three or four miles without varying very percepti- 
bly from a dead level. Along the east and west section line two miles north of 
McPherson one may go 10 miles without passing a sag of more than 20 feet. As 
a rule there is just enough slope to the surface for good drainage, while occasion- 
ally the water stands in lakes and basins in slight swales in the surface. The 
largest basin is nearly three miles in diameter, and is situated two miles west of 
McPherson. The largest lake is Lake Inman, 10 miles southwest of McPherson. 
The divide between the Arkansas and Smoky Hill rivers passes through this 
area and averages a little more than 1,500 feet A. T.* The Arkansas river at the 
southeastern limit is 1,290 feet, A. T., a fall of 200 feet in 60 miles. The Smoky 
Hill river, at the nearest approach, is within four miles of the divide, but its bed 
is nearly 200 feet below it. The Little Arkansas river drains the entire area of 
the Equus beds, except a very small portion north of the divide drained by the 
Smoky Hill, whose tributaries are rapidly cutting into the divide, and will cause 
it to migrate farther to the south in the course of time, as the streams at the 
south are already at their base levels and are not carrying away the soil to any 
considerable extent. i 
STRUCTURE. 
These beds consist of alternating layers of clay and sand, with a stratum of 
‘‘ volcanic ash’’ in a part of the northern area. Near the bottom of the deepest 
part of the channel is a heavy stratum of gravel, which passes through McPher- 
son, Harvey county, and Halstead, respectively. This bed lies at a depth of 140 
to 150 or more feet at McPherson and contains an abundance of water, as it does 
wherever itisfound. The upper part of the gravel stratum grades into a stratum 
many feet in thickness, which is partly argillaceous and partly arenaceous, some- 
times 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. Over this, and also extending over a 
slightly undulating Permian floor for 15 miles to the east, is a stratum of sand vary- 
ing in thickness from 30 feet (at McPherson, according to Prof. 8. Z. Sharp) to 
three feet in places farther east, but averaging six or eight feet in thickness. This 
stratum also contains a good supply of water. It covers the entire area of the 
Equus beds except, perhaps, 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”’ 18 to 24 inches thick. Nod- 
ules of calcium carbonate are frequently found in both the upper and lower 
strata of clay. They are irregular, but generally show a slight roundness of 
form. Some of these are quite hard, while others are quite 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 (CaCOs), the orthorhombic 
form of calcium carbonate.’’ No structure could be determined in the hard nod- 
ules. Doctor Grimsley pronounces the ‘‘ volcanic 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 the Dakota sandstone and sand from the 
Dakota sand-hills were also pronounced of the same character, except differing in 
* U.S. topographic sheets. 
