INNER BORDER OF THE GRAND RIVER LOBE. 47 1 



right angles with the moraine and in tlie direction of the ice movement, and 

 their construction gravelly, they are regarded as small eskers. 



The most prominent instance noted of this class of ridges remains to 

 be described. Along Lackawannock Creek from its mouth, at the "big 

 bend" of the Shenango southeast for 1^ miles, there is a large di-ift ridge 

 30 to 40 rods in width and 40 to 75 feet in height. It is quite continuous 

 for about a mile, and extends in the form of disconnected knolls for one- 

 half mile farther. The main ridge has knobs and basins along its crest 

 and on its slopes. There are also along its south side occasional low drift 

 knolls. The valley in which it lies is 100 to 120 rods wide (two to three 

 times the width of the ridge). The surface of the ridge is gravelly, but no 

 deep exposures occur. It is probably an esker, though it is broader and 

 has a more hummocky surface than eskers commonly have. Its trend 

 harmonizes with the ice movement, as shown by strise in that vicinity. It 

 does not connect with the moraine oil the southeast, nor does it have an 

 esker fan at its terminus. The valley in which it lies has its head within 

 2 to 3 miles southeast, on quite elevated upland, and there are few drift 

 knolls in its upper course. 



DEUMLINS (?). 



In Lewis's report^ is a description of a "rounded hill of compact till" 

 lying in the Shenango Valley at Sharpsville. The description led the writer 

 to suspect that it might be a drumlin, but an examination shows that its form 

 is due to erosion, it having been cut off by ravines on the one side from 

 the remainder of a quite extensive tract having the same altitude as the top 

 of the hill, while its lower side faces a lower plain of the Shenango Valley. 

 No drumlins were observed by the writer within the district covered by the 

 Grand River lobe; but Chamberlin reports having observed hills with 

 drumlin form in the vicinity of Corry, Pa., though they may have a rock 

 nucleus. 



TILL PLAINS. 



The drift on the uplands is very largely till, and constitutes in Ohio a 

 considerable portion of the " clay belt" or "dairy lands" previously described. 

 The till is thickly interspersed with fragments of shale from the districts 

 farther north. It has not the porous structure that characterizes the moraine, 



' Second Geol. Survey Pennsylvania, Kept. Z, pp. 188-189. 



