Vol. 36 



i 



No 12 



BULLETIN 



OF THE 



TORREY BOTANICAL CLUB 



DECEMBER, 1909 



The plant formations of the Nockamixon Rocks, Pennsylvania 



John W. Harshbergkr 



After the Delaware River is joined by the Lehigh River, it 

 flows ahnost due south, but in a sinuous course for a distance of 

 ten miles to a point a mile below Riegelsville, then it flows south- 

 eastward a mile and five-eighths to Kintnersville. At this place, it 



M 



J 



The 



south bank of the river rises between Kintnersville and Narrows - 

 ville into a series of precipitous cliffs known as the Nockamixon 



Rocks (figure i). More accurately, \( the east sheet o{ the 



topographic map of Bucks and Montgomery counties (No. 12, 

 Pennsylvania Geological Survey, Final Report) is consulted, these 

 cliffs are found to be situated between 75° 6' and 75° 10' west 

 longitude and 40° 34' north latitude. The boldest rocks frown 

 down on three miles of the river's bank (figure 2). According 

 to the Pennsylvania survey, the crest of the cliffs is 500 feet 

 above the river. The cliffs form a sheer wall oi rock in many 

 places (figure 3), cut by ravines down which the streams tumble 

 in cascades, or waterfalls. An expert mountain-climber might 

 ascend the precipitous rocks, but a less expert climber must 

 clamber the ledges of rock from cascade to cascade in the severa 

 ravines that seam the rocks. As the streams that descend from 

 above have an extremely limited watershed, they usually run dry 

 durihg the summer months and little pools are left in the hollows 

 of the water courses, where the wild birds are accustomed to drink. 



[The Bulletin for November, 1909 (36 : 615-650. //. J0-J4) was issaed i6 N 

 »909 ] 



651 



