292 GEOIiOaT OF ohio. 



scmth it is usually bordered by irregular, billowy dunes of sand — the 

 lidge, apparently, formed by the waves, the dunea by the wind. Pre- 

 cisely the ssrbe results are now produced by the combined action of the 

 wares and wind where low, swampy land extends to the lake, and the 

 shore is bordered by a sand beach. 



The following section, near the Norwalk water- works, will exhibit th® 

 relations of the same ridge to the underlying clays of the drift ; 



FT. 



1. Sand 40 



2. Tfellow clay, wHIt irregnlar blocks of bin* elay, enrroimaed with a yel- 



low oxydized shell 20 



3i Sand, with a profusion of vertical eolramnar coBcretMm», at the bottom, 



passing into yellow clay 10 



4. Blue clay, finely washed, compact,, mingled with sharp, fine graTel, the 

 whole eat by Tertical, obli(jiie, and horizontal seams — the greater 

 part TertJcal — filled witb yellow, silicsous clay, cemented into rock.. 20 



The partingg in this blue clay vary in thickness, from that of paper to 

 one-eighth of an inch, and are so finely cemented, that where the clay ia 

 washed away by the rains, they resist the erosion, and project from the 

 bank from three-fourtha of an inch to one and a half inches. The 

 cementing raaterial is iron, brought down from the clays above, and the 

 fissures are apparently cleavage seams, produced by compression. 



A few rods to the north of this locality, the well for the Norwalk 



water-worka was eiink in the valley, and commences on a level with the 



bottom of the bluff, of which the section is given above. The materials 



passed through were — 



rr. 



1. Yellow drift clay, passing, into Woe clay 17 



2. Gravel to bottom 5 



The fragments of rock thrown out in the excavation, were principally 

 granite, green stone, corniferous limestone, and Huron shale. Near the 

 bottom of the blue clay, in this well, was obtained the remarkable spheri- 

 cal concretion originally from the Huron shale, one side of which was 

 planed o^ and striated by glacial action, which is figured and described 

 by the Chief Geologist, Prof. Newberry, in the first chapter of volume 

 one. It was obtained seventeen feet below the surface of the valley, and 

 one hundred and seven feet below the base of the sand ridge at Norwalk. 



There is ordinarily no such a,ceumulation of drift material beneath the 

 sand ridge, as is indicated above. "West of Monroeville,^ the ridge is a 

 regular, well marked beach line, rising about ten feet above the plain at 

 the south of it, and fifteen feet above that at the north. On the south 

 side, are the irregular dunes mentioned above, and on the north, a wide 

 stretch of level prairie land. 



