284 E. H. WILLIAMS, JR. EXTRA MORAINIC DRIFT. 



South of the Ridge the Bushldll and the streams between it and the 

 Delaware flow into the latter river, as do those in the Durham valley and 

 in the small valley just north of it. In the great valley a divide from 

 Topton to Germansville separates the waters of the Lehigh from those of 

 the Schuylkill. The main affluents of the Lehigh are the Manokis}^ and 

 Hokendauqua from the north, the Jordan and Little Lehigh from the 

 west, and the Saucon from the south. Those of the Schuylkill are Maiden 

 and Sacony creeks. The Durham and Saucon valleys are separated at 

 Leithsville by a narrow divide in quartzites at 445 feet, and with slopes 

 of 71 feet per mile eastward, and 114 feet per mile westward. Between 

 the Saucon and the small valley north of the Durham there is a narrow 

 divide in gneiss at Stouts, at 505 feet, with a sharp slope of 225 feet per 

 mile on either side. There are other and higher divides that do not 

 enter into the discussion of the Saucon valley. 



In the main valley the Lehigh-Schuylkill divide has been noted at 

 Topton. It is in limestone at 495 to 510 feet and does not vary 10 feet 

 in two miles along its crest. The surface of the valley from the divide 

 to Allentown varies little from a slope of 20 feet per mile for 14 miles, 

 while to the west it falls 40 feet per mile for 3 miles to Sacony creek ; 

 thence to Kutztown it rises 119 feet per mile for three-fourths of a mile, 

 and falls to the small creek to the west 71 feet per mile. From this place 

 to Moselem Springs the rise is identical in grade and length with that 

 from the Sacony to Kutztown ; and from the Springs to the Schuylkill is 

 a fall of 25 feet per mile for 7 miles. The Sacony and the small creek 

 to the west both flow north to Maiden creek. Attention is called to the 

 peculiar direction of this flow, as Avell as to the fact before noted, that 

 the northern edge of the valley is 80 feet lower than the southern one. 

 The Topton divide is therefore the only one of the three that is higher at 

 the northern end. It is also worthy of notice that the streams east of 

 the Topton divide flow south through the slate belt and east and Avest 

 when they reach the limestone, while west of that divide the directions 

 are reversed. 



As all of the divides noted have been covered with drift, their eleva- 

 tions above tide at the close of giaciation may be relatively determined by 

 the slope of their sides and the width of the valleys in which they occur. 

 As those at Stouts and Leithsville are in narrow valleys with high and 

 steep sides and their own sides slope 71 to 225 feet per mile, the rainfall 

 from the extensive highlands would be concentrated on a small area, so 

 that they must have been denuded much more than the wide divide at 

 Topton. with its level and broad valley, where all the water that fell to 

 the northward was diverted immacdiately westAvard, and only that from 

 the southern highlands performed erosive Avork. When Ave consider 



