386 THE ICE AGE IN NORTH AMERICA. 



Gannet's table of levels, which is very scanty in that portion 

 of Kentucky, it would appear that the height of the water- 

 partings between the Licking and the Kentucky is not 

 greater than that of the ridge running south from Cincinnati 

 between the Licking and the Ohio ; so that such an outlet 

 may exist somewhere in that vicinity. 



But I have not been sure that the water did not pass 

 around the immediate margin of the ice reaching the Ohio at 

 the mouth of Woolper Creek, about thirty miles below Cin- 

 cinnati, where the celebrated post-glacial conglomerate known 

 as Split Eock is situated. This formation consists of pebbles 

 now firmly cemented together by infiltrations of lime. The 

 mass rises one hundred and sixty feet above the river. The 

 most of the pebbles are limestone from the Cincinnati group, 

 but there are mingled with them granitic pebbles which 

 show it to be a glacial deposit. On Middle Creek, a little 

 lower down in Boone county, the same conglomerate is found 

 at a still higher level, running up to four hundred feet ; and 

 at various places on the road to Big Salt Lick uncemented 

 gravel, which is unquestionably of glacial origin, caps the 

 tops of the hills at about the same height. It is not unlikely, 

 therefore, that much of the outflow from around the dam 

 was in the immediate vicinity of the ice-front. 



Professor E. W. Clay pole, in an article* read before the 

 Geological Society of Edinburgh and published in their 

 " Transactions," has given a very vivid description of the 

 scenes connected with the final breaking away of the ice-bar- 

 rier at Cincinnati. He estimates that the body of water held 

 in check by this dam occupied twenty thousand square miles, 

 and that during the summer months, when the ice was most 

 rapidly melting away, it was supplied with water at a rate 

 that would be equivalent to a rainfall of one hundred and 

 sixty feet in a year! This conclusion he arrives at by esti- 

 mating that ten feet of ice would annually melt from the 



* " The Lake Age in Ohio," " Transactions of the Geological Society of Edin- 

 burgh,'' 1887 



