GLACIAL PHENOMENA OF NORTH AMERICA. 69 



bash. The marks of this enormous accumulation in the 

 channel of the lower Mississippi are seen in the bluff 

 deposits and the Orange sands, investigated by Prof. 

 Hilgard. 



Coming east, the first river entering the sea below the 

 boundary of the glaciated region is the Delaware. This 

 has a small drainage area, and is so situated with ref- 

 erence to the Catskill Mountains and the Aljeghanies that 

 even in glacial times it never could have been rein- 

 forced by northern ice accumulations like the rivers far- 

 ther west. The terminal moraine crosses the Delaware 

 at Belvidere, a. few miles above its junction with the 

 Lehigh and a few miles below the Delaware Water Gap. 

 The portion of the drainage basin above this point does 

 not exceed 6000 square miles. Still the melting of the 

 2000 or 3000 feet of ice which accumulated over that 

 area must from the nature of the case have produced im- 

 portant results in the valley below. Following down the 

 river from Belvidere about sixty miles, we descend some- 

 thing over 200 feet to tide level. Through this distance, 

 the valley is somewhat constricted, and the river is every- 

 where bordered by a terrace of coarse gravel from fifteen 

 to twenty feet above present high- water mark. At Tren- 

 ton, where tide level is reached, this gradually passes 

 into an extensive accumulation three miles vyide and 

 more than forty feet above high-water mark. It is here, 

 in the accumulation of coarsely stratified pebbles and 

 gravel and sand, that Dr. C. C. Abbott has found so 

 many palaeolithic implements. Below Trenton the forma- 

 tion gradually diminishes and grows finer until at Phila- 

 delphia it is scarcely distinguishable. This accumulation 

 of river gravel is entirely distinct from the deposits of 

 yellow gravel which cover southern New Jersey. It is 

 later also than the Philadelphia brick clay. This clay 



