times curvilinearly. Sometimes its crystals are dodecahedral. and 

 approaching to the rhomboidal. Its hardness is such as yields 

 easily to the knife, its transparency considerable, its fracture con- 

 choidal, and its specific gravity 1.666. Like amber, its crystals 

 become electric by friction, but not unless previously insulated. 

 It is insoluble in water, and therefore communicates no taste to it. 

 Being heated in a retort, it is decomposed, and yields a bituminous 

 and empyreumatic water, carbonic acid, and a concrete volatile 

 salt; a carbonaceous residuum being left. When placed on burn- 

 ing charcoal, or in a heated crucible, it burns like combustible 

 vegetable matter ; leaving a greyish white matter, which has all the 

 characters of alumine, mixed with a small portion of lime. This 

 substance therefore appears to be composed of alumine, bitumen, 

 a small portion of lime, and a peculiar acid, which resembles in 

 many of its properties the oxalic acid, but differs from it materially 

 in others. This acid is decomposed very speedily by heat, evapo- 

 rating in a dense smoke ; and by distillation yields a considerable 

 quantity of carbonic acid. When the constituent parts of this 

 substance are considered, with the situation in which it is found, and 

 the substances with which it is associated, there can be but little 

 hesitation in admitting it to be produced by the subterranean de- 

 composition of vegetable matter, and therefore to belong to that 

 class of natural productions of which we are here treating. The 

 appearance which this substance presents may be pretty correctly 

 known by reference to the representation of it, Plate I. Fig. 2. 



The bituminous nature of JET is indisputable, it being plainly 

 evinced both by its chemical and physical properties. Indeed it 

 often manifests so exact a resemblance, in every respect, except in 

 its colour, to arnber, as to have occasioned it to be named, as has 

 been already remarked, black amber. The blackness which distin- 

 guishes it has never yet been satisfactorily accounted for, and in- 

 deed offers to our consideration a question difficult of solution. 



