548 DOMAIN VI. CARBONACEOUS. 



quartz; the bed or vein which it contains, is 

 nearly three yards thick ; the graphite is there 

 found in large masses, but of different degrees of 

 quality ; what is not good, is thrown away. 



" Pencils, which are enclosed in cylinders of 

 wood, are made of graphite. In France they 

 are called mine de plomb, or capuchines. The 

 pieces of graphite are sawn in very thin quadran- 

 gular sticks, which are put in a groove made in 

 one of the halves of the wooden cylinder, which 

 is to form the envelope of this fragile pencil. 



cc The dust of the graphite, mixed with gum, 

 forms pencils of an inferior quality. 



" This same dust serves to lay over iron, and 

 especially cast iron, to keep them from rust; 

 mixed with grease, it is used very efficaciously 

 to diminish the frictions in wheel engines. 



" Also, mixed with argil, at Passau in Ger- 

 many, they make crucibles of it, which resist 

 extremely well sudden transitions of temperature, 

 and which are used by smelters. 



" Laminar graphite is often formed artificially 

 in the flaws of cast iron, and in the cavities of 

 furnaces where iron is used. M. Fabroni af- 

 firms that it is also sometimes formed in the 

 humid way; and cites, on this occasion, the pits 

 dug in the territory of Naples : an acidulous 



