Frazcr,] ^51j [April 20. 



group, and the lean copper shales of the Catskill, none but still more in- 

 signirieant exhibitions have been noted in other formations. 



It might be easier to account for cupriferous shales and sandrocke in 

 the Triassic beds were we sure that ferriferous and cupriferous Huronian 

 rocks were actually in contact with their lower surface, and provided also 

 we could find evidences of such cupriferous and ferriferous horizons among 

 the rocks of the South Mountain system, which are evident lateral continu- 

 ations of the bed ot the Mesozoic sea. 



It is true that a copper horizon has been noted in the Orthofelsite of the 

 South Mountain, as at Watson's, Snj^der's, etc. in Adams County near 

 Monterey ; and deposits of Micaceous and Specular Iron Ore of very great 

 beauty at G. Coles' near the summit of the Gettysburg-Chambersburg turn- 

 pike (both of these in the Iluronian series) : and also that many minor oc- 

 currences of specular and magnetic iron ore disseminated through the rock 

 in minute crystals (as in specinaens found on Green Ridge near Caledonia 

 Springs, etc.) ; but all the deposits thus far discovered will not account for 

 the exceptionally rich character of that portion of the Mesozoic beds which 

 abuts upon the eastern tlank of the South Mountain.* 



In my report of progress for 1875 (Second Geol. Survey of Penn. CC, p. 

 328), I have given reasons for the rejection of any theory which implies a 

 local deposit of these ores (/. e, only along the borders of the formati(m), 

 and I have cited eleven localities scattered over the length and breadth 

 of the Mesozoic belt in York and Adams Counties where micaceous ore ap- 

 pears — more or less mixed with magnetite. The copper horizon of 

 Pho'nixville seems at first sight to agree well with the views advanced by 

 Dr. Hunt and others concerning the restriction of the metalliferous strata 

 to the two edges of the New Red, for Phoenixville lies very near the south- 

 ern edge of this formation on the Schuylkill, where it has dwindled down 



* Dr. T. Sterry Hunt, in a recently published paper on tlie "Cornwall Iron 

 Mine and some related deposit.s in Pennsylvania," states as follows: 



" But I have now to bring to your notice" * * * " those ores which are found 

 " over Pennsylvania along both borders of the iNIesozoic red .sandstone forma- 

 " tlon which stretches through the State; including on the south side the ores 

 " of Warwick and the Jones Mine, and on the north side a line of deposits from 

 " Boyirtown and the vicinity of Reading to beyond the Susquehanna, includ- 

 " ing the great Cornwall Mine near Lebanon." 



"These ores were by Prof. Rogers referred to what ho designates the Primal 

 " slates, which he regarded as the lowest member of the Palreozoic series, though 

 " by some later observers the Cornwall Mine and certain related deposits west 

 " ol the .Susquehanna have been referred to the Mesozoic sandstone. It would 

 '* be foreign to my present purpose to set forth the reasons which lead me to 

 " conclude that these are, all of them, really contemporaneous deposits included 

 " in the Primal slates, which corresponds to a portion of the lower Taconic se- 

 " ries of Emmons, and belong, in my opinion, to a lower horizon than the 

 " Potsdam sandstone of the New York system. That they are met irith only along 

 " the borders of (he Mesozoic sandstone formation is due to the fact that those ancient 

 " ore-bearinf/ rocks, from their decayrd condition and their inferior liardness, have 

 " beenrernoved by denudation, except vhrn jiroteeted by the proximity of the newer 

 " sand.Hones or of eriijitire rurks, ax i.i the ccic <it the Cornindl Mine." 



(Transactions American Institute of Mining Engineers, Vol. IV, p. 320J 



