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it has since been ascertained to be a peculiar acid, differing in some 

 of its chymical properties, and in its affinities, from other acids. 

 If the distillation be continued, the fire being augmented after the 

 succinic acid is come over, a thick brown oil, which yields an acid 

 taste, will be then distilled. But if water be employed in the dis- 

 tillation, a clear light oil will come over, which darkens by keeping, 

 first becoming of a yellow, and then, by degrees, even of a dark 

 brown colour. 



JET is a compact, opaque, and very black substance, of almost 

 a stony hardness ; capable of receiving a high polish, and breaking 

 with a conchoidal fracture, and a glassy lustre. Its specific gravity 

 is 1.259. On being rubbed it manifests electric attraction ; when 

 heated it yields an odour resembling that of asphaltum, but not so 

 powerful ; and when inflamed, by a strong heat, it burns away, 

 leaving an earthy residuum. It yields by distillation a bituminous 

 oil, and an acid, which seems to resemble that of amber. 



The term succinum nigrum, or black amber, has been applied by 

 several ancient writers to this substance; and indeed with much 

 propriety, it seeming to be the bituminous substance next in purity 

 to amber, and approaching the nearest to it in its several pro- 

 perties. It may be considered as possessing the intermediate place 

 between the purer bituminous matters and coals, it holding a suffi- 

 cient quantity of charcoal to give it blackness ; but has not suffered 

 that kind of change which serves to correct the disagreeable odour 

 which the less altered bitumens yield on the application of heat. 



Although the surface of jet sometimes bears a striated and lig- 

 neous appearance, its conchoidal fracture evinces that closeness 

 i)f structure which does not determine its separation, in any one 

 particular direction more than another. Plence it is employed 

 to form various trinkets, such as beads, buttons, &c. it yielding 

 pretty readily to a careful application of the instruments of the 

 turner. 



