178 hitelUgtnce and Miscellanies* 



5. Notice of the Plwnbago of Ticonderoga : by Professor 



Hall. 



Middleburij College, August '2.1, 1822. 



TO PROFESSOR SILLIMAN. 



I do not remember to have seen in the "American Jour- 

 nal of Science," any account of the Plumkago, Graphite, or 

 Black Lead, found on Cobble Hill in the town of Ticonde- 

 roga. That which occurs in the vicinity of Roger's Rock 

 has been frequently described. I visited the locality on 

 Cobble Hill, last week. It is about three miles N. W. from 

 the Upper Falls. The Plunribago is found in numerous 

 places, on the south side of the hill, in deep veins, from 

 one to eight inches in thickness. The veins are, generally, 

 perpendicular to the horizon, and nearly parallel with each 

 other. The gangue is graphic granite. 



Near the summit of the hill, the plumbago is disseminated in 

 all parts of the gangue, occurrii^g, sometimes in small nodules, 

 but oftener, in thin laminae, exhibiting a brilliant metallic lustre. 

 Some of the plates are very large. I measured one which 

 was an inch and one twelfth in diameter. Among the gangue 

 at the most elevated locality, is found a greenish stone, ex- 

 tremely hard, which in its external appearance, resembles 

 Green Hornblende, but it is too hard for that mineral, I 

 am at a loss what it is. 



The graphite, in veins, is uncommonly pure. It occurs, 

 here and there, in irregular, hexahedral prisms. I saw very 

 little that was granular. Most of it is foliated. In a {evt 

 instances, it appears to he fibrous ; but, on examining it more 

 closely, you perceive that the fibres, which are often long, 

 running across the whole vein, are composed of narrow, thin 

 laminae. It is removed from its gangue by means of chisels, 

 pick axes, and iron bars, and conveyed to the Falls, where 

 it is pulverized and purified. It has been prepared for the 

 market, chiefly I>y Guy C. Baldwin Esq. who informed me, 

 that about three tons are disposed of annually. The average 

 price, at which it is sold, is sixteen dollars a hundred. 



