1885.] NATURAL SCIENCES OF PHILADELPHIA. 169 



tauqua County, N. Y., and resting upon the water-shed between 

 Pope Run (a tributary of the Allegheny) and Case Run (a tribu- 

 tary of the Conewango), the moraine is finely shown as a ridge 

 of till, which, stretching completely across the valley, and 

 covered by numerous boulders of gneiss, rises upon the 

 highlands on either side. The moraine ridge here, as in other 

 places, is most prominent behind or toward the west. 



A very small marginal kame runs westward and down-hill 

 from the back of the moraine, in Chautauqua County, as though 

 a subglacial stream had drained the moraine backward, into the 

 valley of the Conewango. The moraine itself is apparently 

 unstratified, and no drift was noticed in front (E.) of it. Its 

 only drainage, therefore, must have been backward, into the 

 Conewango. 



An interesting double kame, consisting of two ridges of sand 

 united into one, the double anticlinals being exposed, was 

 observer by the writer in Mercer County. 1 It is probably not 

 a true marginal kame. 



An examination of the marginal kames, of which sufficient 

 examples have now been given, leads, as has been seen, to the 

 conclusion that they were made b} r subglacial streams draining 

 the edge of the ice-sheet. The occasional boulders and till on 

 top of, but not in, these kames argue a subglacial origin, the 

 boulders and till having been dropped by the retreating glacier 

 on the kames : while the position and direction of each of the 

 kames described is just such as would be taken by streams 

 flowing beneath the ice-sheet. Among the facts ascertained with 

 regard to marginal kames are their water-worn and stratified 

 character ; their rude anticlinal structure, often of finer sand 

 within than without ; the presence of occasional boulders and 

 even till on top of them ; the absence of any fixed relation to the 

 movement of the glacier ; the genei'al coincidence of their 

 course with that of the natural drainage ; the total absence of 

 shells, driftwood, beach-marks, or other indications of the action 

 of ocean currents, waves or tides ; their intimate connection with 

 the terminal moraine in such positions as to indicate a backward, 

 as well as a forward subglacial drainage. 



These kames are very different from those tongues of stratified 

 drift which often occur in or near the glaciated region at the 



1 Report Z, p. 191. 



