155 
it has since been ascertained to be a peculiar acid, ditFering in some 
of its chemical 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 aw’^ay , 
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 approaches the nearest to it in its several properties. 
It may be considered as possessing the intermediate place betwmen 
the purer bituminous matters and coals, it holding a sufficient quan- 
tity 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 
of structure which does not determine its separation, in any one 
particular direction more than another. Hence 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. 
