302 PROCEEDINGS OF THE ACADEMY OF [1880. 



aronncT the " Bear Swamp," had its other extremity near the 

 house of Di\ C. C. Abbott, below Chambei'sburg. This village was 

 under water. Another ba}^ extended up the valley of Crosswicks 

 Creek. Boulders of Champlaiii age lie upon the Tertiary" gravels 

 which form the ancient banlv. 



From the extent of the Trenton gravel in this vicinity, state- 

 ments have been published that it covered the whole southern part 

 of the state, and that at the time of its deposition the Delaware 

 Rivel' emptied into the ocean at Trenton. It is evident tliat the 

 distinction between the very different gravels of this region has 

 not been perceived. Careful examination will show the great dis- 

 similai'it}^ between the Trenton gravel and such gravels as occur 

 at Princeton Junction and interior New Jersej^, which are in 

 great part of Pliocene age, and will prove that it is confined to 

 the ancient river bed. 



The presence of very large boulders on the river bank at Tren- 

 ton has led some geologists to suppose that the formation was a 

 glacial moraine. The occasional though ver}' rare examples of 

 scratched pebbles and polished boulders, which the flood had evi- 

 dently carried down from the moraine material north of Belvidere. 

 have been brought forward as supporting this theory. Yet the 

 absence of till and of angular masses of rock, and generally of 

 materials foreign to the Delaware Valley, when regarded in con- 

 nection with what we have shown to be the general characters of 

 the formation, can not be explained upon this theorj^ The char- 

 acter of the river banks along the valley render the presence of a 

 glacier at Trenton extremely improbable. These show no marks 

 of glacial action. We have, moreover, already shown that 

 the Trenton gravel is more recent than the deposits of Cham- 

 plain age, and that, lying in a channel cut within them, it is 

 the most recent of all the gravels. Clearly the Delaware Valley 

 and the channel of the river were excavated in a time previous to 

 the deposition of the Trenton gravel. The channel subsequently 

 having been filled up by this gravel, the diminished river still 

 later has cut a new channel either completel.y through it, as at 

 Trenton, or partially, as at Philadelphia. It is probable that 

 slight undulations of the level of the coast have aided in producing 

 these changes. 



Before describing the human relics found in the Trenton gravel, 

 there are several facts bearing upon its origin and age which it 

 will be well to consider. 



