50O . GEOI,0«T OF OHIO. 



Guelph horizon. Of coiTrse, surface rock is here alluded to, for, beneatk 

 the Niagara group undoubtedly occur all other Paleozoic series. Hither 

 the great glaciers of the north, at a very remote age, have transported 

 and deposited all over this rocky floor, in varied depths, vast quantities 

 of clay, sand, gravel, and bowlders, on an average of a hundred feet or 

 even more. Through the action of water, or the hand of man, where 

 there was no other impediment than a few feet of soil, in five different 

 localities, small areas of the native rock have been exposed. Conse- 

 quently little or nothing can be known of the topographical features 

 of the underlying beds of rock, though the character and constitu- 

 ents can be as perfectly, known as were the whole open to view. We 

 must know, however, that being a limestone of somewhat irregular 

 texture, in many places soft and sandy, in others hard and crystalline, 

 and subject to the violence of enormous glaciers, that it would certainly 

 present a very haggard, cut-up surface were its covering ikot so complete- 

 In those few insignificant areas the beds appear perfectly horizontal and 

 unbroken, save one exception, and that is unusually interesting, as- 

 indicating the relative situation of Greenville, and the ancient channels 

 of Greenville and Mud Creeks. 



In visiting Dr. Gard's quarries, which are about a mile and a half 

 south-west of Greenville, between the fork of Greenville and Mud 

 Creeks (but a little nearer the latter), it is first noticeable that the beds 

 of rock are considerably folded, dipping toward the south and east ; 

 and also the fact, that in quarrying, the rocks suddenly stop in the adja- 

 cent Drift, the strata being traceable for a short distance by scattering 

 fragments of limestone as torn off' and left. In the digging of the public-- 

 cistern on the corner of Fourth Street and Broadway, the Niagara ledge- 

 of rock was struck at a depth of ninety-five feet below the surface. The 

 cistern, though a failure, so far as obtaining an abundant supply of wa- 

 ter was concerned, inadvertently furnished knowledge that has proved 

 useful in other ways. This measurement may also be regarded as the 

 minimum, for at no place in the vicinity, in the sinking of wells, has it. 

 been reached at a lesser depth. 



Gard's quarries lie about twenty-one feet below Greenville, conse- 

 quently seventy- four feet above the rocks underlying the town. The 

 same ledge of limestone crops out at Bierley's, a!)out four and a half mil,e& 

 east of Greenville, and fifteen feet higher than the beds last mentioned. 

 At Weaver's Station, about five miles south of Greenville, Mud Creek 

 runs over the horizontal Niagara limestone thirty-five feet higher than, 

 the same. Consequently, all these facts, together with much other con- 

 current testimony whic^ might fee given, go to show that Sreenville is 



