A specimen of black lignite from Sussex gave an oil which resembled the former in smell, and perhaps did not differ much from it in its solubility in naphtha, but I had not enough of the substance to institute an accurate comparison, neither in fact, could it serve any purpose. A similar substance from Bovey gave similar results.
The oil which was distilled from jet was of a greater specific gravity than any of the preceding, and smelled strongly of petroleum. It seemed to be soluble in naphtha as readily as the specimen of petroleum with which I compared it. Indeed had it not been that a greater quantity of acid was given over in this process than from any of the varieties of coal, I know not that any chemical distinction between the two would have existed. The mineralogical one is still considerable. The several specimens above enumerated, yielded each a large portion of acetic acid, marking as clearly as the peculiar sort of oil did, the remains of unchanged vegetable matter.
Examining therefore the alteration produced by water on common turf, or submerged wood, we have all the evidence of demonstration that its action is sufficient to convert them into substances capable of yielding bitumen on distillation.
That the same action having operated through a longer period has produced the change in the brown coal of Bovey, is rendered extremely probable by the geognostic relations of that coal. From this to the harder lignites, surturbrand and jet, the transition is so gradual, that there seems no reason to limit the power of water to produce the effect of bituminization in all these varieties, nor is there aught in this change so dissonant from other chemical actions, as to make us hesitate in adopting this cause. In the ordinary process of vegetable putrefaction and destruction, a variety of compound gases are formed by the reaction of their elements, and carbon alone, or rather carbon united to a portion of hydrogen, remains behind.