in some other coal-beds, of which I have procured accounts, the surface of the coal beneath clunch or clay is of an inferior quality, as at West Hallum in Nottinghamshire. The clunch probably from hence acquires its inflammable part, which on calcination becomes vitriolic acid. I gathered pieces of clunch converted partially into alum at a colliery near Bilston, where the ground was still on fire a few years ago. The heat, which has thus pervaded the beds of morass, seems to have been the effect of the fermentation of their vegetable materials; as new hay sometimes takes fire even in such very small masses from the sugar it contains, and seems hence not to have been attended with any expulsion of lava, like the deeper craters of volcanos situated in beds of granite. 3. The marine shells found in the loose sand-rock above this reservoir of petroleum, and the coal-beds beneath it, together with the existence of sea-salt beneath these coals, prove that these coal beds have been _at the bottom of the sea_, during some remote period of time, and were afterwards raised into their present situation by subterraneous expansions of vapour. This doctrine is further supported by the marks of violence, which some coal-beds received at the time they were raised out of the sea, as in the collieries at Mendip in Somersetshire. In these there are seven strata of coals, equitant upon each other, with beds of clay and stone intervening; amongst which clay are found shells and fern branches. In one part of this hill the strata are disjoined, and a quantity of heterogeneous substances fill up the chasm which disjoins them, on one side of this chasm the seven strata of coal are seen corresponding in respect to their reciprocal thickness and goodness with the seven strata on the other side of the cavity, except that they have been elevated several yards higher. Phil. Trans. No. 360. abridg. Vol. V. p. 237. The cracks in the coal-bed near Ticknall in Derbyshire, and in the sand- stone rock over it, in both of which specimens of lead-ore and spar are found, confirm this opinion of their having been forcibly raised up by subterraneous fires. Over the colliery at Brown-hills near Lichfield, there is a stratum of gravel on the surface of the ground; which may be adduced as another proof to shew that those coals had some time been beneath the sea, or the bed of a river. Nevertheless, these arguments only apply to the collieries above mentioned, which are few compared with those which bear no marks of having been immersed in the sea.