COMBUSTIBLE MINERALS, NOT GASEOUS. 183 



choidal, more or less perfect, earthy and slaty. Lustre resinous. Ranges from transparent 

 to opaque. Hardness 0.0 to 2.0. Specific gravity from . 83 to 1 . 20. Inflammable, and 

 gives out a bituminous odour when burnt. 



Varieties. This species has often been divided into two, under the names of Mineral Oil, 

 and Mineral Pitch or Bitumen ; the former of which includes the liquid varieties, and the 

 latter those which are solid. But they imperceptibly pass into each other. 



Naphtha. A yellow or yellowish white transparent liquid, which burns with a white flame, 

 and gives out a penetrating odour. It dissolves the resins. 



Petroleum. This includes the blackish brown translucent or opaque liquid varieties. It is 

 rather thicker than common tar, emits a thick black smoke when burned, and leaves a black 

 coaly residuum. 



Naphtha, when exposed to the air and light, becomes brown, and seems to pass into petro- 

 leum : and when petroleum is distilled, a liquid is obtained similar to naphtha. 



Mineral Pitch, Asphalt, and Elastic Bitumen. These names are sometimes applied to the 

 solid varieties. They are usually of a brownish black colour. The first has an earthy and 

 uneven fracture ; the second has a conchoidal fracture, and is opaque and brittle ; while elastic 

 bitumen yields easily to pressure, is flexible, elastic, and closely resembles caoutchouc. They 

 all burn readily, giving out much smoke. The soft varieties harden by exposure. 



Composition. Naphtha, Carbon 82.20, hydrogen 14.80 {Thomson). Elastic Bitumen, 

 Carbon 52.25, hydrogen 7.49, oxygen 40.10, nitrogen 0.15 (ifenry). According to Kane, 

 the formula for Asphaltum is CioHajOe. 



Geological Situation. Some of the varieties are most abundant in the coal formations, 

 and seem to be connected with them ; others are found in Umestone and sandstone rocks, and 

 do not appear to be peculiar to any geological period. 



Uses. In countries where this mineral abounds, it is frequently used as fuel. Asphaltum 

 enters into the composition of certain hydraulic cements, and into that of the black varnishes 

 called _;apans, for coating iron vessels. Naphtha is employed as a solvent of caoutchouc, and 

 the common petroleum is in repute as a medicinal article. 



LOCALITIES. 



Albany County. Petroleum is found in considerable quantities, floating on the surface of 

 a spring near McKown's, in the town of Guild erland. 



Allegany County. A celebrated locality of petroleum, known by the name of thfe Seneca 

 Oil Spring, occurs in the town of Cuba, within about eighty rods of the line which divides 

 this county from Cattaraugus, three and a half miles from the village of Cuba, and twenty-one 

 miles from Angelica. It is a circular pool about eighteen feet in diameter, filled nearly to its 

 margin with foul water, and having no visible outlet. The water is coated with a thin layer 

 of the mineral oil, giving it a yellowish brown colour, but the quantity is inconsiderable. The 



