io6 The American Geologist. August, i904. 
It is more often pure white, but sometimes colored by iron 
oxide. At Crystal city, Pacific, Augusta and Westpoint it is 
capped by the First ]\Iagnesian' limestone. The fact of its 
being so pure and easily crushed caused extensive plate glass 
works to be constructed at Crystal city and these have now 
been successfully operated for thirty years. Xear Horine in 
Jefferson county, it is seen 80 feet thick and thence northwest 
to Pacific it is of frequent occurrence. Onte hundred feet 
thickness is exposed at Pacific, the upper seventy-five feet be- 
ing pure white and easily hauled. There has been a large 
quantity shipped ofiF from here for the past twenty-five years. 
At Valley Park, a few miles east, extensive glass works have 
recently been constructed. 
At Gray's summit the Pacific railroad cuts through this 
sandstone. 
On the Missouri river at St. Albans it is the lowest rock 
seen an'd at Lefficue Rock it is in the river. 
The hill, one mile below Augusta in St. Charles county, 
shows the following section : 
1. 16 feet of Lower Trenton, on the hill top. 
2. 94 feet of First Magnesian liinestone. 
3. 2 feet of coarse calcareous sandsione, somewhat oolitic and en- 
closing calc spar. 
4. I foot of earthy oolitic limestone with calc spar. 
5. 2 feet of white and brown sandstone, slightly oolitic. 
6. 130 feet of white Saccharoidal Sandstone. 
7. 2j^ feet of chert. 
8. 3 feet of dark, rough, mottled magnesian limestone. 
9. 38 feet of Second Magnesian limestone, containing some chert 
and some Cotton rock beds. 
A half mile east, along the bluffs, the Second ^Magnesian 
limestone dips beneath the horizon and one mile farther the 
sandstone disappears. From here, as we go west, as far as 
Boone, the standstone is found near the top of the Alissouri 
blufifs. On Tuque creek, two miles north of Marthasville, it 
is 127 feet thick and pure white, with the lower beds slightly 
brown tinged. A cave called "the devil's boot" occurs near 
Alarthasville. From the level surface we descend 30 feet to 
the floor. We are there in a room 60 feet wide and 150 feet 
deep, 8 feet high at the entrance and 25 feet high at the far- 
ther end. There is a cave near the head of the Dry fork of 
Charette which has a beautifully ripple marked roof. 
