GRIMSLEY. | Gypsum Mines and Mills. files 
The natural bridges found here represent remnants of old 
caves or underground water channels whose roofs have partly 
fallen in. One of the best of these natural bridges is found on 
Bear creek, south of Sun City, as shown in Plates XX VI and 
XXVII. Itis thus described by Professor Cragin in the paper 
to which reference has already been made: 
‘‘This bridge spans the canon of the creek, here about fifty-five feet from 
wall to wall. The height of the bridge above the bed of the creek is at the high- 
est point forty-seven feet, at lowest thirty-one, and at middle thirty-eight. The 
width of the bridge at the middle is thirty-five feet. The upper surface of the 
bridge declines toward the down-stream side, but not so much that a wagon 
drawn bya steady team could not be driven across it. The thickness of the arch 
is therefore greater on the up-stream side, where it measures twenty-six feet, 
than on the down stream. The relief of the vicinity seems to indicate that ata 
geologically recent time Bear creek here flowed to the east of its present course, 
and that its waters, becoming partially diverted by an incipient cave, enlarged 
the latter, and finally were wholly stolen by it, the cave at length collapsing, save 
at the portion now constituting the natural bridge.”’ 
Other Lesser Deposits. 
GYPSUM IN THE COAL MEASURE SHALES OF SOUTH- 
EAST KANSAS. 
In numerous places in the Coal Measure shales of southeast- 
ern Kansas, gypsum crystals are found in comparative abun- 
dance, but not in sufficient quantity to be of any considerable 
economic importance. They are usually in the soil and clay 
near the surface. The size of the crystals vary from those of 
microscopic dimension to almost an inch in diameter, with the 
majority of them ranging from one-eighth to three-eighths of an 
inch. Sometimes in a corn field one has to dig less than six 
inches to find them. Elsewhere the last washing of a heavy 
rain exposes them along the bank of a little stream. 
They probably have originated principally through the action 
of solubleiron sulphate on calcium carbonate, the iron sulphate 
having been produced by the decomposition of pyrite. The 
shales in the vicinity of a gypsum deposit are usually quite 
heavily charged with pyrite. As weathering decomposes the 
shales the pyrite changes to iron sulphate, and is carried here 
and there until it comes in contact with the limestone abundant 
in such localities. One of the noticeable features of such locali- 
