350 



15 minutes this ceased, and the retort being red .hot, a small quantity of 

 water dropped from the beak into the receiver ; and, as it there collected, an 

 oily, or sublimated film, appeared on its surface. The strongest heat of this 

 furnace was continued about an hour ; when evident absorption taking place, 

 and the distillation ceasing the operation was stopped. Upon opening the 

 receiver, a strong empyreumatic smell was observed. The liquor obtained has 

 a dull yellow colour, with small scales on its surface, and in quantity about 

 20 drops ; the greatest part of the scaly substance adhered to the receiver on 

 pouring out the fluid. The substance in the retort was still pulverulent, but 

 much more white than when introduced. The liquid shows no acid properties, 

 by the test of litmus paper, or violets. 



I am, with much respect, 



W. H. PEPYS,jun. 



The oily, or sublimated film, and the strong empyreumatic smell, 

 afford some reason for believing in the presence of bitumen in this 

 opaline wood ; but anxious, only for the discovery, and communi- 

 cation, of the truth, I wish you to suspend your opinion, until your 

 judgment has been aided by other corresponding experiments, 

 which I shall now adduce. 



Common pitch-stone, that which displays no obvious trace of 

 wood, hols-opal of Emmerling, and, from its resinous or pitchy 

 lustre, the pierre de colophane of De Lisle, and the pierre de poix of 

 Daubenton, differs in no respect from the former kind, except in 

 the absence of those marks which give to that a resemblance to 

 wood. Believing this to depend merely on the bituminous wood, 

 which enters into the composition of this latter substance, having 

 become so fluid as to have had the remains of its fibrous structure 

 quite melted down, whilst in the former some of the fibrous struc- 

 ture remains, I conceive it not entitled to be considered as of a dif- 

 ferent family from the former, as has been done by the celebrated 

 Mr. Kirwan, and other mineralogists. In proof of this opinion, we 

 often see, in the same specimen, in one part, distinct fibrous appear- 

 ances ; in another part of the same substance, the fibrous appear- 



