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which are often marked by impressions of plants, &c. Thewaterv particles being exuded, and hardness effected, isobserved to have been the case in balsams, gums, caoutchouc,and many other vegetable glutens, into which a portion ofwater enters in their original composition, whilst existing ina liquid slate; those substances becoming once dry andhard, it is diilicult again to unite them with that element.The particles of earthy matter, which may have beensupposed to have sunk with the bitumen, are accountedto have formed the floor or bed for the bituminous mass,having from their superior density gravitated through it.Yet we have seen the proportion of earths still discoveredupon chvmical analysis, above stated, to have been acciden-tally detained in the substance of coals; which does notmilitate against the last position. Much of the matter ofcoal, likewise, mixed with various earths and metallic par-ticles, also form the schistose or roof of coal-beds, which iscombustible and burnt for ordinary purposes, affording ano-ther argument of the descent of that matter in a state of fluid-ity, anil presumed to be formed as previously described : aswere also the different par tings, so technically termed, whichare small vacuities observable between the strata serving forcovering and the substance of coal itself: this also evidencesa belief that the body contained, must have suffered somediminution in bulk; and what mode can account so well forthis appearance, as to imagine it to have been produced bythe operations previously detailed, and that of drying andhardening.
Moreover, bitumens also, in a fluid state, are still fre-quently found in the neighbourhood of coal. In FrancbeCompte, at their coal-mines, bitumen exudes plentifully indrops, which their miners call guhr, (tears of the mines.)
The high degree of combustibility to which the substanceof coal is subject, is temporized by intermixture of someincombustible particles with the grand mass of combustiblematerial, which serves nearly to insulate and surround thecombustible particles. This appropriate division could nothave been effected, had particles of earthy matter, in anyconsiderable degree, been suffered to intermix with the puresubstance.
An additional argument, to pibve the truth of the positionwe have embraced, also appears in this, that the earth whichcovers the fossil wood of Munden, Professor Hollmanalleges to be combustible, from the bitumen it contains. Asimilar observation is also made on the earth at the Boveymines, as described by Dr. Milles, and as having the samequality. It is a fact sufficiently notorious, that in the neigh-