method therefore I expected to detect not only the progress of bituminization from simple turf to jet, but to assure myself whether in the examinations hitherto made by others of these different substances, any mistake had arisen from confounding the vegetable bitumen with true bitumen when distillation was used to investigate their nature.
Vegetable turf in all its varieties, as well as brown coal, gave a considerable colour to lixivium of potash, but the same menstruum produced no effect on jet, or surturbrand. Nor had naphtha or alcohol any action except on the resinous lignite of Bovey, from which they extracted the resinous matter which that variety contains.
I therefore subjected these different substances to distillation, trusting that by the produce, I should ascertain, not only the fact, but the progress of bituminization.
Submerged wood, from peat mosses in Cumberland, gave a brown oil, smelling of the wood tar and refusing to dissolve in naphtha. In this case therefore, no appearance of a change towards bitumen was exhibited. A compact pitchy looking peat gave an oil which had a fetid smell, neither resembling that of wood tar, nor bitumen, and which was very slightly soluble in naphtha.
The Bovey brown (board) coal, produced an oil of a peculiar smell, but most resembling that of wood tar, and much more soluble in naphtha than the preceding. Having a larger quantity of this, I separated the soluble part by naphtha, and in the remainder, or insoluble oil, the smell of wood tar was powerful, notwithstanding the strong odour of the naphtha. Here then the progress of bituminization had advanced another step. The resin of this wood, on which a particular name has lately been bestowed, I consider as an adventitious and accidental substance, and the natural produce of the tree, now probably unknown, which occupies these alluvial strata, as other lost productions of Nature are detected in other alluvial soils.