Notice of Geological Surveys. 133 



merous salt wells of this state in some cases extend to this forma- 

 tion, and in others do not reach it. 



9. The " coal Tneasures'^ which succeed this are composed as 

 usual of repeated series of limestone, sandstone, shale, iron ore and 

 coal, and are particularly described in this Journal by Dr. Hildreth. 



The organic remains are of the common coal plants — Lepido- 

 dendra, two feet in diameter, Calamites of great size, and Sigil- 

 laria with their bristling spines perfectly preserved and standing 

 out in every direction, with numerous ferns. The inclination of 

 the coal measures is east south east, thirty five to forty feet in a 

 mile, and the direction north north east, with a thickness in 

 Muskingum county of twelve hundred to fourteen hundred feet. 



Between the blue and cliff limestone are the ^'^ great marl stra- 

 tum," one hundred and six feet thick, and the ^-flinty limestone," 

 well developed in Adams county. The former is blue and stra- 

 tified — by the action of frost and weather it becomes lighter col- 

 ored, and when dry is almost white. 



''It is earthy, highly effervescent, contains few fossils, and is 

 traversed by thin layers of reddish slaty limestone, two or three 

 inches thick." 



The ^^ flinty limestojie," like the "blue," lies in thin layers in- 

 terstratified with marl, but differs from it in color, in fossils, and 

 especially in having certain layers filled with silicious matter in 

 chemical combination, (not arenaceous,) has the sharp, conchoidal, 

 flinty fracture, and fires with steel ; oftentimes very much brok- 

 en up in small triangular pieces — in others an excellent building 

 stone, and never appears weathered. Cyathophylla and Crinoidea, 

 of various forms, and corallines, are observed in a few strata. 

 Chert, (or flint ?) in nodules, is found in Indiana and at Cincinnati, 

 in the soil, and they become more numerous as we approach Ad- 

 ams county, where they are found in their native bed in this 

 formation. This suggests the idea that it once extended much 

 farther west. 



II. Report of a Geological Survey of Indiana, 1839, hy D. D. 



OiVEN, M. D. 



The examination of this state, though general, has been ex- 

 tended to almost everyone of the old counties, and its geology is 

 so like that of Ohio, that details in its description may not be ne- 



