108 



AX AMERICAN GEOLOGICAL RAILWAY GUIDE. (PA.) 



173. "Round Top," " Cemetery Hill," "Macfarlane's Hill" and " Gulp's Hill," forming th e 

 ridge on which the Union Army fought the great battle of Gettysburg, July 2d and 3d, 1863, are all 

 trap dikes. This is a good place to study these curious formations. The scenery is beautiful and 

 full of historical interest. (See the description of the 16. Triassic formation.) 



174. By Charles A. Ashburner, assistant on the second geological survey of Pennsylvania. 



175. Jack's Mountain on the west, 5 a. Medina, with 5 b. Clinton fossil ore on its flanks. Blue 

 Ridge, 5 a. Medina, in the distance on the east. End of Chestnut Ridge, southeast from station, 

 composed of Lewistown on 9 Upper Helderberg limestone and 8 Oriskany sandstone. 



176. On the east Blacklog Mountain, 5 a. Medina. Shade Mountain also Medina. Blacklog 

 Valley. Between them is anticlinal 3 c. Chazy and 4 a. Trenton limestone. 



177. Coal openings on both sides of the railroad. The two upper seams worked, the lower 

 seam not worked. 



178. The Huronian (?) is here decomposed into Kaolin. 



179. The road runs on the edge of the Azoic, masked by drift all the way to Wilmington. 



ELEVATIONS. The elevation above tide water of every railway station in Pennsylvania can be 

 found in Report N. of the Second Geological Survey of this State, by Charles Allen, Assistant 

 Geologist, 1877. 



