372 GLACIAL FORMATIONS OF ERIE AND OHIO BASINS. 



cubic feet or more, but the majority contain only 10 to 20 cubic feet. They 

 are largely granitic rocks and fine-grained greenstones, but quartzites and 

 conglomerates from the Huroniau ledges of Canada are also common. 

 Very few limestone or local bowlders of any kind occur. The vast majority 

 of the bowlders are partially rounded or subangular, but scarcely one in 

 one hundred shows glacial planing. They lie on the surface, or are but 

 slightly embedded in the ground. From accounts given by residents it 

 appears that very few are struck in making wells or other excavations 

 except within a foot or so of the surface. The large proportion of crys- 

 talline Canadian rocks, the slight amount of glacial planing, and the 

 restriction of the bowlders to the surface, individually as well as unitedly, 

 indicate that the bowlders were englacial, becoming superglacial at the 

 border rather than subglacial; but the underlying drift appears to be 

 largely subglacial, being composed of thoroughly intermixed local and 

 distant material whose rock fragments are much more conspicuously gla- 

 ciated than are the surface bowlders. If this interpretation be correct, the 

 amount of englacial material was very slight compared with that of the 

 subglacial.^ 



This bowlder belt continues beyond the limits of the Miami lobe at 

 each end, being traceable southwestward along the eastern limb of a 

 moraine of the East White lobe some 12 to 15 miles, when it loses its 

 strength and can with difficulty be traced farther. In the Scioto moraines, 

 as noted elsewhere in this report, bowlders are present from the reentrant 

 angle in Logan County southward for 30 miles or more in greater abun- 

 dance than throughout the remainder of the loop, but not in such great 

 numbers as in the Miami lobe. If these continuations of the bowlders into 

 the Scioto and East White lobe be included, the length of the bowlder belt 

 will be increased to about 160 miles. There ajjpears to be no reason for 

 separating the bowlders in the other lobes from those in the Miami lobe. 

 Indeed, they seem to have been deposited at the same time and serve a 

 valuable purpose in indicating the correlations of the moraine. 



The outer member of this morainic system has comparatively few 

 bowlders on its surface, the only points where noteworthy numbers were 



^Comp. Chamberlin: Third Ann. fiept. U. S. Geol. Survey, pp. 331-332; Am. Jour. Sci., May, 

 1884, pp. 378-390; Bull. Geol. Soc. America, Vol. I, pp. 27-28; Jour. Geol., Vol. I, pp. 47-60. Upham: 

 Am. Geologist, Vol. VIII, Dec, 1891, pp. 376-385; Bull. Geol. Soc. America, Vol. Ill, pp. 134-148. 

 Salisbury: Am. Geologist, Vol. IX, May, 1892, pp. 304-316. 



