And if, as seems probable, the coaly matter is continually changing into asphalt and oil, and then working its way upward through every crack and pore, to escape from the enormous pressure of the superincumbent soil, it must needs carry up with it innumerable particles of the soils through which it passes.

" They went together, and Burnley bade Hope observe that the water was trickling through in places, a drop at a time; it could not penetrate the coaly veins, nor the streaks of clay, but it oozed through the porous strata, certain strips of blackish earth in particular, and it trickled down, a drop at a time.