94 



AN AMERICAN GEOLOGICAL RAILWAY GUIDE. (PA.) 



Pennsylvania. 



1. This line runs along the Delaware river over alluvion and modified glacial drift, based upon 

 Azoic rocks, upon which lie the bottom layers of the Cretaceous of New Jersey. 



2. Here the line finally leaves the Azoic rocks, across a fault, and passes white marble quarries 

 to the Westchester Valley, rocks vertical, and probably identical with those of western Vermont, 

 (Taconic ?) 



3. Beds of quicksand. Wharton's famous nickel mine not far off. 



4. From here to Elizabethtown, over the garden of Pennsylvania, the great limestone plain of 

 Lancaster; steep dips; plications and faults innumerable; geology wholly unknown. 



5. Zinc mines recently opened and worked one mile to the east. 



6. Eoad runs for a mile or two along the back of a greenstone trap dike, twenty miles long, 

 extending from the Cornwall iron mines near Lebanon, to the Susquehanna river at Falmouth, and 

 over it into the great greenstone trap region of York County. Good place to study the action of 

 the trap rock in metamorphosing the beds of New Red. 



7. Commencement of the great cross section of the Paleozoic Rocks, and south edge of the 

 limestones of the Great Valley. 



8. Finest section in the State here. Seven miles thickness of rock, nearly vertical but slightly 

 overturned, so that the upper formations seem to plunge beneath the lower may here be 

 measured, viz : From the Hudson River slates (Lower Silurian, or Siluro-Cambrian), up to the 

 Coal Measures on the summit of the Third Mountain. 



9. Here a greenstone trap dike, only 4 feet thick, 35 miles long, crosses the road and river. It 

 carries iron ore. One mile west a coal bed is opened in the Pocono Sandstone, the representative 

 of the New River Coal System of Montgomery County in Virginia. Five miles east, in the notch 

 in the summit of Peter's (Fourth) Mountain, where the Dauphin-Halifax turnpike crosses its crest, 

 is a vertical wall scored horizontally with glacial stria. Notice the terrace which the Catskill 

 makes on the north flank of Peter's Mountain opposite Duncannon; it is the finest exhibition of 

 Catskill terrace erosion in the State. See Notes 77 and 170. 



10. Clinton fossil ore bed extensively worked here and at Mifflin. 



11. Best place to study the Juniata River coal system, (Hamilton; Lower Devonian). 



12. Long Narrows. River flows in a narrow synclinal between anticlinals of Medina and 

 Oneida. 



13. Best place to study Oriskany glass sand quarries, one mile back of McVeytown on the 

 opposite (north) side of river. 



