AND COAL-MEASURES OF IOWA. 113 
cent. of carbonate of lime, 15 per cent. of silica, and 7:5 per cent. of oxide of iron, 
which exists in the state of protoxide; the light gray, less than half the quantity 
of carbonate of lime, 53 per cent. of silica, and not quite 2 per cent. of protoxide of 
iron. It is much inferior in quality to the dark, earthy variety; indeed, it is hardly 
entitled to be considered hydraulic. 
Towards the mouth of Soap Creek, are good sections of the middle argillaceous 
division of the coal-measures. On Section 3, Township 70 north, Range 12 west, 
three seams of coal are seen in the midst of a mass of bituminous shale, as shown 
on Section No. 19, D. The two lower seams are the thickest, being about two feet 
each. The coal is slaty in its character, and presents the appearance of charcoal 
on the cleavage surfaces. The strata pitch with an irregular dip to the northeast, 
so that the corresponding beds are considerably lower on the Des Moines River, 
opposite the mouth of Soap Creek—a distance of a mile and a half—than they are 
at this locality. 
Two miles above the mouth of Soap Creek, at “ Cedar Bluffs,” on the Des Moines, 
heavy beds of sandstone, constituting the lower members of the upper division of 
the coal-measures, overhang the shaly beds, and rest immediately on an inferior 
thin seam of slaty coal, charged with sulphuret of iron, passing rapidly into the 
state of sulphate of iron. The latter appears in the form of light green crystals, 
efflorescing from the edges of the coal, which are protected from rain by the projéct- 
ing ledges of solid gritstones. Thin carbonaceous seams and specks are disseminated 
through the inferior beds of sandstone, together with imperfect vegetable impres- 
sions. Thirty-five feet of sandstone is exposed at this locality. (See Section No. 20, D.) 
There are probably two or more seams of coal hidden from view in the slope by the 
rubbish, which conceals from twenty to thirty feet of the lower part of the Section. 
The shale contains some calcareous bands and septaria; some of which may have 
hydraulic properties. From the cavities of these, very regular crystals of calcareous 
spar were obtained. 
Near the mouth of Turkey Creek, light buff sandstone, containing irregular veins 
of carbonaceous and coaly matter, lie within two feet of the water, and extend to 
the height of twenty-five feet; the rock is filled also with imperfect impressions of 
Calamites, Sigillarice, and Equisetacee. Some of the beds are irregularly schistose, 
others sufficiently thick to afford a tolerable building-stone, if fairly quarried into. 
From one and a half to two miles below this, close-textured, light-coloured lime- 
stone was observed in the bed of the river, with a schistose sandstone near the 
water-level. On Sugar Creek, a few rods above its mouth, there are solid ledges of 
limestone running across the bed of the river, with an easterly dip, forming a fall 
of about two feet. On Section 28, Township 72 north, Range 13 west, on the same 
Creek, and at the water-level, is a seam of coal, three feet thick, overlaid by two and 
a half feet of dark gray, bituminous limestone. In digging a well at Mr. Farlin’s 
house, near by, an eighteen-inch bed of coal was struck, which, by estimation, must 
lie about five feet above the afore-mentioned limestone. Both beds of coal rest on 
shale, and the upper bed is covered with eight feet of the same material. The rock 
in the hills above is chiefly sandstone, with a bed of coal and shale immediately 
15 
