1913.] NATURAL SCIENCES OF PHILADELPHIA. 125 



the north border are found to show features which suggest the 

 transportation of a considerable part of their materials by ice 

 floating in streams arising from the melting of glaciers in the Appa- 

 lachian Mountains to the north. 



Explanation of Plate III. 



Map of the north border of the Triassic in Bucks, Northampton and Lehigh 

 Counties, Pennsylvania, showing distribution of the border conglomerates and 

 hypothetical stream channels of Triassic times. 



