NOTICES OF MEMOIRS. 
61 
the bitumens, still plastic, flow together from various cen- 
tres of emission and coalesce into a more or less extensive 
aggregation of the substance. The “ Pitch Lake ” of Tri- 
nidad is- merely an instance of this coalescence on a larger 
scale than usual. 
Mr. Wall then shows that this view of the production of 
bitumen, (namely, by direct conversion) is not new, having, 
been expounded by Bischof twenty years ago. 
Some remarks follow as to the production of bitumen 
from animal remains for which there are many well-known 
evidences* among which is the mountain limestone (of 
Derbyshire &c.) which, where highly fossiliferous, contains 
bitumen in the cracks and joints, evidently derived from 
the animal substance of the fossil remains. 
R. J. L. G. 
At the Academy of Sciences (Paris,) on April 23, Mr. 
Berth elot presented a note “ On the Origin of Carbides 
and combustible Minerals,” in which the author, starting 
with the hypothesis of Mr. Daubree that free alkaline 
metals may possibly exist in the interior of the globe, sup- 
poses that carbonic acid comes into contact with these 
metals, and passes through a series of chemical changes 
resulting in bitumen, petroleum, &c. Thus the author 
conceives a purely mineral origin for these natural carbides. 
(See the Chemical ITetvs, 5th May.) 
R. J. L. G. 
