33° Mr. Knox's experiments and observations 
100 grains of the brown part of the residuum of this pitch- 
stone were then fused, as before, in a platina crucible, into a 
light-grey glass ; it lost one per cent. ; thus making up the 
5 per cent, which had been the loss from the original fusion. 
Experiment 11. 
400 grains of Arran pitch-stone lost by ignition 4,5 per 
cent. ; and when distilled in the usual manner in an iron 
retort, one grain was collected in the receiver, possessing a 
very peculiar smell. The contents of the retort were a per- 
fect enamel. The receiver was washed with sulphuric ether, 
which was suffered to evaporate, and a substance remained 
on the glass pan, but too small in quantity to enable me to 
examine it. 
Experiment 12. 
Artificial pumice. 
100 grains of artificial pumice, which had been the result 
of my first and second experiment, were fused in a platina 
crucible into a greyish-white glass. It lost nothing. 
OBSERVATIONS. 
I shall, for the sake of distinctness, divide my remarks 
under heads, beginning with the analysis. 
Analysis. 
Having mistaken the bitumen which appeared so frequently 
in the course of all my analyses of the stone, for manganese, 
and having found, I think, that inflammable substance* in the 
* Vide Experiment. 
