59 



shales, with igneous intrusions like the Palisades and the trap 

 ridges at Princeton and Hopewell and along the Delaware 

 River, and the Watchung ridges. The Piedmont plains are 

 usually 100 or 200 feet ahox-e sea-le\-ol, somewhat hic^hcr in the 



First Watchung Mountain: quarry West Orange — 

 showing columnar structure. 



north. Westward and northward of the Watchung Mountains 

 lies the so-called New England province, composed of geologi- 

 cally very old rocks (schists, gneisses, and much granite in- 

 trusive), all Pre-Cambrian and underlying the other two 

 provinces. Two prongs extend southwestward from New Eng- 



