352 



have offered, of substances possessing this peculiar lustre, deriving it 

 from an impregnation with bitumen, and are in full accordance with 

 the experiments of Mr. Pepys. Mr. Klaproth introduced 100 grains 

 of this substance into a small glass retort, inserting its neck into a 

 bottle containing lime-water. The retort was placed between the 

 coals, or in open fire, and the heat gradually increased to the igni- 

 tion of its contents. At the very beginning there passed over some 

 drops of water, and soon after the lime-water in the receiver became 

 turbid. In this last, when the receiver was removed, a bituminous- 

 empyreumatic smell was perceived, which at first also seemed to be 

 somewhat ammoniacal. The pieces of the stone, in the retort, 

 were rendered Wack, and resplendent like jet ; but by a still longer 

 ignition, in an open crucible, they lost that black colour, and be- 

 came at first bluish; then grey white, losing, at the same time, three 

 grains more of their weight *. 



The result of this operation, and particularly the bituminous-em- 

 pyreumatic smell, afford pretty strong evidence in favour of the 

 supposed nature and constitution of the substances of this genus. 



Yours, &c. 



* Analytical Essays, by M. H. Klaproth, p. 452, 



