336 Mr. Knox’s experiments and observations 
The darker specimens appear to contain most bitumen, 
nearly 3 per cent. 
The bitumen, as well as the soda, can be separated from 
the stone by the action of nitric and muriatic acid, but the 
bitumen not in a state of purity. 
The bitumen can be obtained pure by distillation from the 
stone by means of a heat nearly approaching to whiteness. 
It can be separated from water by evaporation. The Newry 
pitch-stone is converted into pumice when properly distilled. 
It is magnetic, but not so much so as its pumice. 
It is not electric, either by heat or friction, neither is its 
pumice. 
It probably owes its smell , slatiness, and disposition to dis~ 
integrate , to the bitumen. 
The bitumen probably modifies its colour also. 
The Newry stone agrees, as to its ingredients, with the 
Saxon pitch-stone from Meissen ; but they differ somewhat 
in their relative proportions, and particularly in the quantity 
of bituminous matter. 
The Arran pitch-stone seems also to contain bitumen; but 
on this point I cannot yet form a decided opinion. 
I had begun a course of experiments on other substances, 
namely, green-stone, basalt, obsidian, &c., but I have been 
obliged to discontinue them for the present. I cannot how- 
ever abstain from mentioning one experiment which failed, 
as it was attended by a circumstance which gives it some in- 
terest. 
