1870.] 00 J [Ashburner. 



very limited observation in Blackleg valley. A very distinct palaeontologi- 

 cal break exists between this epoch and tlie underlying auroral maguesian 

 limestone, the upper strata of which are exposed in the centre of Blacklog 

 Valley opposite Rockhill Gap. It is probable that the Magnesian rocks in 

 this part of Pennsylvania are at least 3000 feet thick, which would place 

 the top of the Potsdam sandstone (the lowest group in the Palaeozoic 

 column), at least three quarters of a mile vertically beneath the present sur- 

 face of the centre of Blacklog Valley. 



Localities where the Strata were Measured and Studied. 



No. XIII. 



Nos. 267, 266, 260, 256 and 252. Robertsdale, Trough Creek coal basin, 

 Carbon Township. 



Nos. 265 to 261 inclusive. Coal bed D (Lower Freeport ?) Section 

 measured about 400' from mouth of mine C^ Robertsdale collieries. 



Since the section was compiled, I have been informed by Mr. Wm. A, 

 Ingham, Pres'dent Rockhill Iron and Coal Co., that a bed of black band 

 ore has been discovered in the "Swamps " in mine C, between the bottom 

 bench of coal and the fireclay floor, ranging from 1 to 4 inches thick and 

 yielding 30.79 per cent, of metallic iron. 



Nos. 259, 258 and 257. Coal bed C (Kittannlng ?) Section measured 

 about 200' from mouth of mine B^ Robertsdale collieries. 



Nos. 255, 254 and 253. Coal bed B (Clarion '?) Section measured by 

 Wm. Foster, Esq. in mine A, Robertsdale collieries. 



No. 251. Coal bed A (Brookville?) Section reported by Wm. Foster, 

 Esq. "Monkey drift," Robertsdale collieries. 



No. XII. 



No. 250 to 244 inclusive. Rocky Ridge near Wray's Hill Tunnel, Todd 

 Township and Wray's Hill, Carbon Township. 



No. XL 



Nos. 243, 242, 241 and 240. Wray's Hill and Rocky Ridge. 



No. 239 to 234 inclusive. Wray's Hill Tunnel E. B. T. R. R. 



Nos. 233 and 232. Ground Hog and Plank Cabin Valleys, Carbon Town- 

 ship. 



Nos. 231 and 230. New Grenada, Taylor Township, Fulton County. 



No. 229 to 220 inclusive. Limestone quarry worked by John Whitney, 

 Esq., near Todd P. O., Plank Cabin Valley. 



No. 219. Ground Hog and Plank Cabin Valleys. 



No. 218 to 213 inclusive. Well on Ezra Heater's farm, one mile south 

 of Todd P. O., section reported by Mr. Chas. E, Billin. 



No. X. 



No. 212. Ground Hog and Plank Cabin Valleys. 



No 211 to 124 inclusive. Sideling Hill Tunnel E. B. T. R. R. 



No. 123 to 117 inclusive. Smith's Valley. Clay, Cass and Union Town- 

 ships. 



Tlie total thickness of No. X was verified by measurements made in 

 Sideling Hill Gap, Fulton County. 



