MINERALOGY. 453 



clear flame ; does not change or become solid by being 

 exposed to the air. G. = 0.75. Contains, occasionally, 

 a portion of asphaltum, which renders it of a darker 

 color. If the mixture of asphaltum is sufficient to render 

 it more viscid, it is called Mineral Pitch or Mountain 

 Tar. Occurs in clay, sand limestone, and marl ; abounds 

 on the northwestern shores of the Caspian Sea, Batku, 

 and Modena, near which places it issues from the earth 

 in large quantities, mostly by springs. Petrolium is 

 is used in Birmah as lamp oil. Naptha affords both light 

 and fuel to the inhabitants of Batku, and that obtained 

 from the spring near Amiano is also used for illuminating 

 the city of Genoa. There are also other springs of naptha 

 in Italy, Alsatia, etc. Employed in various ways, it is 

 very useful, first, as affording fuel and light ; secondly, 

 forming a substitute instead of oil for paint, or making 

 varnish, and, in France, in forming cement for covering 

 roofs and lining water cisterns, or making pavements. 



FOURTH ORDER. 



METALLIC EARTHS. 



Graphite Black Lead Plumbago or Carburet of 

 Iron is mostly found either in solid masses, nests, or 

 scate-like laminse ; also granular, and occasionally in 

 prismatic form. Color, iron-gray or black, opaque ; lus- 

 ter metallic ; feels greasy, and does not fuse readily. 

 II. = 1.2. G. = 1.8 to 2.4. Occurs in nests, at Bor- 

 rowdale, England, Chamouny, France, Griesbach, in 

 Passau, and is widely disseminated throughout the East- 

 ern States of North America. The finest sort is used 

 for making pencils. Receives its name, graphite, from 



