140 Mr-. Hatchett’s Experiments on a Substance , 
natural mixture of resin and asphaltum which is found with 
the Bovey coal, we to all appearance have almost positive 
proof that the pit-coals are of vegetable origin. 
True it is indeed, that bitumen has never been formed 
by any artificial process hitherto devised, from the resins or 
other vegetable substances. I have myself attempted it in 
various ways without success, for although I occasionally 
obtained products which resembled it somewhat in odour 
when burned, and other properties, yet the effects of alcohol 
or water always proved these products not to be bitumen. 
But synthesis of natural products, although required in 
strict chemical demonstration, is (as we have but too often 
occasion to know) seldom to be attained, especially when 
operations are performed on bodies whose component parts 
are liable to an infinite series of variations in their proportions, 
qualities, and mode of combination. 
Considering therefore, that bitumen and resin afford by 
certain operations similar products, that resin and bitumen 
are found blended together by nature, and that this mixed 
substance accompanies a species of coal which in many parts 
still exhibits its vegetable origin, whilst in others it passes 
into pit-coal, we may with the greatest probability conclude, 
that bitumen is a modification of the resinous and oily parts of 
vegetables, produced by some process of nature, which has 
operated by slow and gradual means on immense masses, so 
that even if we were acquainted with the process, we should 
scarcely be able to imitate its effects, from the want of time, 
and deficiency in the bulk of materials. 
But although bitumen cannot at present be artificially 
