on the Newry pitch-stone , &c. 329 
been previously very accurately weighed, 0,5 grain of bitumen 
were obtained, equally as volatile as that procured in the last 
experiment. The retort not having received so strong a heat 
as in the former experiments, only a slightly cohering per- 
fectly white powder remained. 
Experiment 10. 
On Arran pitch-stone. 
I fused 100 grains of pitch-stone from the Island of Arran, 
in a platina crucible at a white heat ; it formed an ash-coloured 
glass, and lost 5 per cent. 
400 g ra i ns of the same stone were charged into a green 
glass retort, as in experiment No. 2. Water came over, and 
when the heat was increased, was followed by an oily sub- 
stance ; but at the same moment the neck of the retort fused, 
as in experiment 3, and the distillation ceased. The receiver 
had acquired an additional weight of 16 grains, that is 4 per 
cent. It had the smell of the bitumen from the Newry pitch- 
stone, but faint, and the quantity was too small to be separated. 
On examining the fused retort, it appeared that, for the dis- 
tance of an inch from the bottom, the colour of the stone had 
become, as in former experiments, of an ash-grey, and still 
resembling pumice, but that the upper part was brown, as in 
experiment 3 ; so that it seemed as if the bitumen had risen 
from the more strongly heated part of the retort, and having 
been stopped in its progress by the fusing of the neck, had 
given to the upper part of the mass the same brown colour 
which I had observed when the whole stone had been origin- 
ally ignited in an open crucible, as mentioned in the beginning 
of this paper. 
mdcccxxii. U u 
