SURFACE GEOLOGY. 23 



At Cleveland that portion of the Erie clay which lies above the river is 

 finely laminated and without pebbles or bowlders, but beneath the lake 

 surface, as shown by the excavation for the new tunnel, the clay is thickly 

 set with fragments of shale, and contains a few small bowlders. These 

 are composed of granite, greenstone, or crystalline limestone, brought 

 from the Canadian highlands, and are usually ground off and striated. 

 At the mouth of the old valley of Eocky river the bowlder clay rises to 

 the height of 50 feet above the lake, and the laminated clay of the 

 Cuyahoga valley is wanting;. Twenty miles above the mouth of the 

 Cuyahoga the base of the Erie clay is distinctly shown. It is there a 

 remarkably tough, compact, gray hard-pan, wholly unstratified, and con- 

 taining many rounded and scratched bowlders. It rests upon a mass of 

 fine-grained sandstone, in layers of a foot or more in thickness. These 

 have been much broken up by the ice, and the under part of the clay is 

 thickly set with angular or partially rounded fragments. Where undis- 

 turbed, the ledge of sandstone bears the characteristic glacial marks. 

 Following the valley of the Cuyahoga from its mouth to the summit of 

 the watershed at Akron, we find the following section of Drift deposits, 

 which will show the relations of the Erie clay to the overlying members 

 of the Drift series : 



No. 1. Gravel, sand, and bowlders, more or less stratified, and form- 

 ing hills resting on the Conglomerate, but from which the materials 

 have been washed down, covering No. 2. 



No. 2. Stratified sand and sandy clay ; the latter in many remark- 

 ably even and well-defined alternations, yellow, blue, and red in color. 

 Thickness, 30 to 100 feet. 



No. 3. Finely laminated clay, without pebbles or bowlders ; as a gen- 

 eral rule, yellow where weathered, blue where its iron is protoxide. In 

 two instances striated bowlders of Cuyahoga shale, which forms the 

 rocky walls of the valley, were found imbedded in this laminated clay, 

 evidently dropped into the position they occupy. The greatest observed 

 thickness of this deposit is 90 feet. 



No. 4. Pebbly Erie clay, penetrated by oil wells 228 feet to rock bot- 

 tom of valley. 



In the foregoing section, No. 1 represents a portion of the kames, or 

 sand and gravel series of the highlands ; No. 2, the lacustrine deposits of 

 the upper Drift ; No. 3, the laminated portion of the Erie clay ; and No. 4, 

 its pebbly aspect. The composition of the mass of Erie clay which fills 

 the Cuyahoga valley will be seen from the section given below, taken at 

 the well of the Standard Oil Company, in the city of Cleveland : 



