126 KANSAS ACADEMY OF SCIENCE. 
sum in the central area. This is owned by the Kansas Cement Plaster Company, 
and they now obtain the rock from a 14-foot stratum at the bottom of an 80-foot 
shaft. This rock is white, and much of it is traversed by wavy, dark lines, which 
give a gneissoid appearance, and the plaster made from it is sold under the name 
of ‘“‘granite cement plaster.’? The lower part is compact, and contains the 
rounded crystals of selenite, as in the mine at the north. Through this region 
there is another stratum, five feet in thickness, and 100 feet higher, but it is not 
worked at the present time. 
SEconparRy Deposits. 
Most of the plaster mills of the central area use the earthy gypsum deposits, 
which occur at various places in the region. There are five of these known. 
The first of these was discovered in the spring of 1873, near Gypsum City, by Mr. 
John Tinkler, in running a fire-guard around a field. Two years later he eal- 
cined some of the dirt, as it is locally called, in an ordinary 38-gallon kettle and 
used the plaster in the cellar of his house, where it still remains in good condi- 
tion. In 1889, he, with others, built a mill at the edge of town, but it is no 
longer used. The deposit covers an area of 12 acres, with an average thickness 
_ of eight feet. It consists of a loose, granular dirt, of light ash-gray color when 
dry, and is readily shoveled into cars. It is thusdirectly calcined with less labor 
and expense than is the case with the solid gypsum rock. 
A number of years after the discovery of this deposit, Mr. Gotlieb Heller dis- 
covered a similar deposit 14 miles east, near Dillon station. Another deposit is 
located 314 miles southwest of Dillon, and is five feet thick. In Marion county, 
about six miles south of the last deposit, the Acme Company own a mill and simi- 
lar deposit which is 6 to 10 feet thick. The Agatite Company have another mill 
and deposit at Longford, in Clay county, 35 miles northwest of the Dillon mill. 
All of these deposits lie in low, swampy ground, and strong gypsum springs 
are usually found in them. In most, there is a ledge of rock gypsum at the 
same level or 10 to 20 feet below. The presence of recent shells and bones near 
the bottom of these depesits shows they are recent in age. 
Mepicinté Lopce DEposits. 
The southern Kansas gypsum, with its continuation in Oklahoma and Texas, 
forms the largest area in the United States. Near Medicine Lodge the rock caps 
the hill asa layer 25 feet thick, protecting the underlying soft red beds, thus 
causing the very rugged topography already described. The red clays and shales 
below the gypsum contain interlacing network of selenite and satin-spar layers 
which have been dissolved out of the solid stratum and carried down by circu- 
lating water. In the western part of the area solution has carved out caves and 
underground channels, leaving, in many places, natural bridgesof gypsum. The 
rock is snowy white, and the greater portion has a sugary texture, though the 
lower portion is compact. There are two mills making plaster of this rock. Best 
Brothers own a mill at the town of Medicine Lodge and manufacture the product 
known as Keene’s cement or Robinson cement. This mill has been in operation 
since 1889. The Standard Cement and Plaster Company have a mill west of Sun 
City and manufaeture about 18 tons of plaster per day. This great gypsum area. 
is practically undeveloped at the present time. 
ORIGIN AND AGE. 
I have treated this subject quite at length in a recent paper for the ‘‘ Bulletin 
of the Geological Society of America,’’ which will soon be issued from the press. 
The central and northern rock strata were deposited in an arm of the sea, cut off 
from the main ocean in the lower Permian or Neosho epoch. Farther out in the 
