walcott.] PENNSYLVANIA. 127 



Section No. 3 crosses the Primal slate in Berks County and repre- 

 sents the Primal sandstone dipping southeasterly from the Primal 

 slate forming Mount Pleasant. The Primal sandstone is shown again 

 in Montgomery County at Barren Hill and it is placed in the midst of 

 " Primal mica slate." 



Section, No. 4, in crossing Lancaster and Chester Counties, passes 

 through the Primal series at Neversink Hill, near Reading, and also at 

 Welsh Mountain, where the Primal sandstone is represented as forming 

 a low anticlinal. 



On the line of section No. 5, the Primal sandstone occurs to the west 

 of the Primal slates and gneiss that form Millbough Hill in Berks 

 County. In Lancaster County, on the line of the same section, the 

 "sandstones occupy the south end of Welsh Mountain. In Mine ridge 

 the Primal slates and gneiss are represented as much distorted, while 

 the sandstone forms an anticlinal and synclinal axis. 



Sections Nos. 7 and 8 cross the South Mountain in Adams and York 

 Counties ; and the entire section of the mountain is represented as 

 Primal, as stated in the text. The rocks of Pigeon Hills, to the south- 

 east in section 7, are also referred to the " Primal" and to the u Primal 

 slate, altered and crystalline ; n and the same reference is made of the 

 southwestern extension of the slates of the hills where crossed by sec- 

 tion 8. 



I have been uuable to find any account of original researches upon 

 the Primal rocks during the period between the final report of Prof. H. 

 D. Kogers and the renewal of their study by Prof. J. P. Lesley in 1873. 



In a paper by the latter, on the iron ore of the South Mountain of 

 Cumberland County, a diagrammatic sketch is given of a cross-section 

 of the county at Carlisle, in which the " Potsdam n sandstone rests on 

 the gneiss for a long distance. 1 On the following page a sketch of a 

 section shows the sandstone, resting on the Azoic slates and gneiss ; 

 and beneath is a series of iron ore bearing slates that, in turn, are sub- 

 jacent to the Calciferous sandstone and Trenton limestone. 



In describing the Cornwall iron mines and some related deposits, in 

 Pennsylvania, Dr. T. S. Hunt 2 refers Prof. Rogers's Primal slate of the 

 mines to a portion of the Lower Taconic series of Emmons and beneath 

 the horizon of the Potsdam sandstone of the New York system. This 

 reference carries with it the ores which are found in Pennsylvania 

 along the borders of the Mesozoic and Red Sandstone formations of this 

 portion of the State. 



In another paper Dr. Hunt notes the discovery by Prof. Prime of a 

 species of Monocraterion, in the Auroral limestone of Pennsylvania, 

 and says : 



'The iron ores of the South Mountain along the line of the Harrisburg and Potomac Railway in 

 Cumberland County, Pennsylvania. Am. Phil. Soc. Proc, vol. 13, 1873, p. 4. 



*The Cornwall iron mine and some related deposits in Pennsylvania. Am. Inst. Mining Eng., Trans., 

 vol. 4, 1876, p. 320, 



