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ceive, arises out of the difficulty in our country of acquiring 

 scientific information of a certain kind. The arts of mining and 

 metallurgy are of difficult acquisition every where; they require 

 a great deal of profound theoretical knowledge, and very 

 close practical observation; consequently they are by no means 

 intuitive, and can only be purchased by long, laborious, and in- 

 defatigable exertions, not from books alone, but from the living 

 school where the play of nature has been exposed to view, with 

 the economy of art, where the furnace has taken the place of 

 the crucible ; nor is theory less useful, it is a glorious light 

 which serves to conduct the operative through the dark laby- 

 rinths of practice. 



breccia. 



On the confines of the blue'limestone, which reappears a few 

 miles to the west of York, there is found a breccia composed of 

 a red argillacious cement, and masses of older rocks. The 

 imbedded masses are of various sizes, and the majority of them 

 are limestone, proving its age in relation to the limestone rock. 

 This breccia has a very pretty effect when polished, and might 

 be used for the same purposes as are the common marbles. It 

 continues on, and is seen at the Susquehanna not far from York- 

 haven. You are all acquainted with that beautiful pudding 

 stdtte, out of which the columns that ornament so richly one 

 of the halls in the capitol at Washington have been made. 

 This rock is precisely similar, and like that found on the banks 

 of the Potomac is known in York county, and throughout the 

 United States, as the Potomac marble. 



TRAUMA TES. 



We will pass over in silence the limestone upon which York 

 is located, it having been already described. In journeying in 

 any direction, after leaving the city, from south-west to south- 

 east, you will shortly come to the trau mates of D'Aubuison, 

 phyliades and transition slates of other geologists. These schists 

 are characterized by a more perfect stratification than other 

 rocks in the county ; they are straight, undulating and inclined, 

 and folllow a general direction with the other formations; that 

 is to say, nearly north-east and south-west ; the layers are di- 



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