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gree of induration. It is a light, brittle, brown or blackish sub- 

 stance; showing, when broken, a conchoidal fracture, with a glassy 

 lustre. It manifests a bituminous odour, when rubbed or heated. 

 It melts easily, and is very inflammable; burning away, when 

 pure, without leaving any ashes. Its specific gravity, according to 

 Kir wan, is from 1.0? to 1.65. 



Asphaltum has been spoken of by Dioscorides, and other writers 

 before him, by the name of pissasphaltum; this name, according to 

 Pliny*, being applied to it, on account of its being mixed with 

 common pitch. Agricola-f, however, denies this, and contends, 

 that it derives this name from the circumstance of its odour so 

 much resembling pitch. 



MINERAL CAOUTCHOUC, or ELASTIC BITUMEN, appears to dif- 

 fer from mineral pitch, merely in the degree of elasticity which it 

 possesses ; which seems to be the consequence of the confinement 

 of air, or of some other elastic fluid, in its interstitial cavities. 



Having thus furnished you with the most obvious characters of 

 bitumen in its simpler states, I shall proceed to show you, that at 

 very remote periods, and in various parts of the world, the peculiar 

 appearance and properties of bitumen procured it a considerable 

 degree of attention. 



You w r ill not only find that it furnished the early writers in na- 

 tural history with an interesting subject of inquiry, but that it was 

 known to mankind, as a substance capable of being applied to va- 

 rious economical uses, in the earliest ages of which we possess any 

 authentic record. 



Noah, we are told, coated over the ark, within and without, 

 with pitch]:. The builders of the tower of Babel employed some 

 bituminous matter as a cement ; " they had brick for stone, and slime 

 had they for mortar ." Of the vessel of bull-rushes, in which Moses 



* Lib. xxiv. cap. 1, t De Natura Fossil. lib. iv. p. J95. 



% Genesis, chap. vi. ver. 14. Genesis, chap. xi. ver. 3. 



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