84 



LIMESTONES 



OF RED CEDAR, 



near by, which has been opened in the prairie bottom, is composed of thin, even- 

 bedded limestones, containing nests of calcareous spar. It afforded, however, but 

 few or no fossils. 



On the high ground between the Rapids and Marion, on Section 15, Township 

 83 north, Range 7 west, of the 5th Principal Meridian, freestones like those of the coal 

 series occur; whilst, a quarter of a mile north of this place, both buff-coloured 

 magnesian, and Avhite, compact limestone are in place. 



In sinking wells on the prairie on which Marion stands, a schistose limestone is 

 struck at a depth of from thirty to thirty-five feet. The soil and subsoil are 

 usually fifteen feet deep. Beneath these, a stiff, blue clay sets in, sometimes pass- 

 ing into yellow clay, enclosing water-worn pebbles. Under this clay is an ancient 

 vegetable mould, intermixed with sticks, leaves, and timber. This soil rests upon 

 the above-mentioned limestones. 



Water rises plentifully to the height of seven feet in the wells, on penetrating 

 the ancient soil. 



Small particles of lead ore are reported to have been found in digging the 

 foundation of the court-house at Marion. It is possible, however, that it may have . 

 been pyrites, or blende, ores which are of more frequent occurrence in the forma- 

 tions prevalent in Linn County. 



Where the Tipton Road, passing through Linn Grove, crosses Big Creek, compact 

 magnesian limestone is overlaid by white and buff-coloured limestone. In the bed 

 of Cedar, in Township 80 north, Range 3 west, of the 5th Principal Meridian, 

 probably on Sections 34 and 27, limestone, possessing a close lithographic texture, 

 is found, at a low stage of the river. 



In Linn County, eight miles north of Marion, and four miles from Cedar, there 

 is a remarkably large boulder, at least fifteen feet in diameter. A horse and 

 wagon standing behind it are entirely hidden. 



The stonecutters of Iowa City are supplied with gravestones from a quarry of 

 cream-coloured limestone, which lies in thin, even-bedded layers, to the height of 

 from thirty to forty feet above Cedar River, in the south part of Township 82 

 north, Range 5 west, of the 5th Principal Meridian. The lowest strata, which are 

 the thickest, hardly exceed eight inches. In some of the layers, small hemi- 

 spherical concretions run in the joints of the strata, as well as through the substance 

 of the rock itself. The best of the slabs approximate in character to lithographic 

 limestone. They are, however, of rather too coarse a texture for fine work. The 

 upper strata are striped with yellow, obliquely to the bedding. On Section 28, 

 Township 81 north, Range 4 west, where the south line of the section strikes the 

 river, above Washington Ferry, the rocks are of the same character as at the last- 

 described quarry, only in rather thicker layers of a yet coarser texture. The 

 lowest layers have very much the aspect of the beds observed on the west side of 

 Clear Creek. A north and south crevice traverses the rock at this place, containing 

 some calcareous spar and ferruginous clay ; but no metallic ores have been disco- 

 vered, the crevice being filled with tumbled wall-rock intermixed with red clay. 

 The strata have a southerly dip of 3°. A corresponding wall of rock is also on the 

 opposite side of the river, which would form solid natural abutments for a bridge. 



