on Bitumen in stones. 
521 
and west boundary, imbedded in basaltic tuff, very near the 
shore. In the neighbourhood are beds of brown coal. 
Lost by ignition 19,4 per cent. 
Produce of distillation 11,42 bituminous water, 4 cubic 
inches of carbonic acid, and 8 of carburetted hydrogen. 
The retort contained a velvet black powder, which being 
transferred to a covered platina crucible and exposed to a 
heat which melted cast iron, remained unchanged. 
The carbone being burned off in an open vessel, there was 
a loss of 4 per cent. When the carbon was removed it 
melted into a slag. 
I was induced by the above experiments, to try whether, 
by igniting this substance under charcoal to prevent the 
escape of the carbon, I might not make black chalk. The 
experiment was successful. The chalk was of a pretty good 
consistency and colour, and was effaced like graphite, both by 
bread and caoutchouc. 
13 . Iron Clay, from Disco Island. 
By ignition it lost 21 per cent. 
Distillation produced a bituminous water, weighing 18,25 
per cent. 
14 . Iron Clay, from Howth. 
By ignition lost 5 per cent. 
Distillation produced 4 per cent of bitumen, with very little 
water. The mass in the retort was a pumice, but approach- 
ing to vitrification, and of a pale violet-blue colour : when 
exposed to a stronger heat in a platina crucible the colour 
changed to greenish-grey. 
mdcccxxiii. 3 X 
