the Hudson and its Tributaries. 



311 



The Springtown B profile found the old channel of the 

 Wallkill about a thousand feet east of the present one and just 

 at sea-level. The old valley is broad and open with a fairly 

 mature aspect. The western channel is also shown but at 1000 

 ft. distance and at plus 65, or 15 ft. above the more northerly 

 section. A divide of 150 ft. separated it from the Wallkill, and 

 we cannot but infer that it was coining down to the larger 

 stream from a source to the southwest. 



It is a striking fact that the Pliocene Wallkill dropped 79 ft. 

 in the mile or less from Line A to Line B and that its valley 

 narrowed appreciably. It may have been on softer slates in the 

 southern section and, encountering the reefs of sandstone char- 

 acteristic of the Hudson Biver series, cascaded over them to 

 lower reaches on the north. Springtown A is the last record 



Fig. 5. 



LI BE RTYVILLE. 



Fig. 5. Crossings of the Wallkill river near Springtown and Libertyville. 



which we have of it. The present Wallkill after combining 

 with Bondout creek forms the Bondout river and enters the 

 Hudson in the deep estuarine gorge at the city of Bondout, 

 which has been previously mentioned. The rock bottom of 

 this estuary must lie at a goodly depth below minus 79. 



The Libertyville section is six or eight miles southwest of the 

 Springtown crossings. It found the Pliocene channel some 

 600 ft. east of the present Wallkill and 120 ft. below it, or at 

 plus 65. Therefore in the intervening stretch, while the mod- 

 ern Wallkill in its meandering course over the drift-filled valley 

 drops 25 ft, the ancient river descended 65 ft. and thus had a 

 fairly steep gradient. It must have been feeling the effects of 

 uplift, although the profiles do not indicate any notable incision. 

 In this section the westerly tributary is not pronounced. Its 



