82 GEOLOGICAL SURVEY OF WISCONSIN. 



by its prevailing lithological characters. We have also obtained its 

 characteristic fossils from huBdreds of localities. The result of our 

 investigation has been to show, that the Water-lime, judged by the 

 area it occupies, with its outcrops, is, in Ohio, the most important of 

 all the Silurian strata. It underlies a broad belt of country on either 

 side of the Cincinnati axis, from the lake shore to Hardin county. 

 There the two belts coalesce, and the Water-lime stretches entirely 

 over the arch, forming the surface rock for nearly a hundred miles 

 east and west. Further south the margin of the Water-lime sweeps 

 around the blue limestone area, exterior to and parallel with that of 

 the ^Niagara. 



" South of the national road, and east of the anticlinal axis, the 

 Water-lime forms a constantly narrowing belt, which passes through 

 the counties of Madison, Fayette, Highland and Adams, to the Ohio. 

 In parts of Adams and Highland it forms a feather edge on the flanks 

 of the Cincinnati arch, beyond which the Huron shales rest directly 

 on the Niagara. This shows that the sea in which the Water-lime was 

 deposited reached but part way up the slope of the old Silurian 

 island." 



The same formation extends westward into Indiana. In western 

 Tennessee it has been recognized in Stewart, Benton, Decatur, Hardin 

 and Henry counties. 



Worthen, in the Illinois reports, refers to the Lower Helderberg 

 epoch a silicious limestone directly overlying the Cincinnati, with no 

 intervention of the ITiagara limestone. " No beds of undoubted 

 Niagara age," says Mr. Worthen (Illinois Keports, vol. I., p. 127), 

 " were ever deposited in southern Illinois, but in their place these 

 silicious limestones, representing in part the age of the Lower Helder- 

 berg limestones, and, in part, the Oriskany sandstone of the New 

 York series, were deposited, resting directly upon the Cincin- 

 nati group of the Lower Silurian." "Again," says Mr. Worthen, 

 giving an account of the geology of Union county (Illinois Eeport, 

 vol. III., p. 36), " the Lower Helderberg formation is similar in its ap- 

 pearance here to the outcrops of it, already described in the foregoing 

 report on Alexander county, and it may be described as a thinly bed- 

 ded, grayish colored, close-textured, silicious and cherty limestone, 

 sometimes argillaceous and shaly, and again so flinty that it is dif- 

 ficult to say whether the flint or the limestone predominates." The 

 flinty character of this formation at certain localities in New York 

 was fully described by Mr. Yanuxem. 



Following the Lower Helderberg northwestward from Buffalo, 

 through Canada, we find rocks with the same lithological characters 



