GRIMSLEY: GYPSUM IN KANSAS. 23 
Medicine Lodge the rock caps the hills as a layer twenty-five feet 
thick protecting the underlying soft red beds, thus causing the very 
tugged topography already described. The red clays and shales 
below the gypsum contain an interlacing network of selenite and 
Satin spar layers, which have been dissolved out of the solid stra- 
tum and carried downward by circulating water. In the western 
Part of the area solution has carved out caves and underground 
channels, leaving, in many places, natural bridges of 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 from this rock. Best Brothers own a mill at the town of 
Medicine Lodge and manufacture the product known as Keene’s 
cement, or Kobinson cement. This mill has been in operation 
Since 1889. The Standard Cement & Plaster Company have a mill 
west of Sun City and manufacture about eighteen 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 old gulf salt 
Was deposited in large amount and forms today an important ad- 
dition to the mineral wealth of the state. No salt is now found 
Close to the gypsum, and if it did exist it has been removed by so- 
lution. The irregular upper surface of the gypsum shows that 
there has been solution in some places where large quantities of 
8ypsum rock have been carried away. 
The swamp deposits of earthy gypsum have probably been formed 
by deposit from springs, aided by wash from the hill-sides; and 
they are recent in age. 
The southern gypsum was deposited in a shallow gulf cut off not 
far from close of Permian time. As in the northern gulf, a salt 
deposit occurs to the southwest in the Salt Plains district, but no 
trace is found near the gypsum. 
TECHNOLOGY. 
There are eleven mills in Kansas engaged in the manufacture of 
Plaster from gypsum, seven use the gypsum rock and four use the 
8ypsum dirt. Nearly the same process is used in all the mills of 
the northern and central areas, except that the mills using the dirt 
do not require the crushing machinery. The machinery is manufac- 
