8

COAL MINES OF

shale, containing impressions of vegetables,and not unfrequently the remains of fresh-water shell fish, with those of animals. Undereach stratum of coal is generally found astratum or layer of greasy indurated clay,called by the miners clunch , and usually des-titute of those organic remains that charac-terize the shale. In some cases the seams con-tinue for a great distance with a regular dip,and rise,: in others they may be representedby muscle shells inverted one into another,and having the open side upwards.

The seams of coal are for the most part se-parated from each other by beds of various-coloured sand-stone, of clay, of bituminousshale, of ratchil, or rubble-stone of a soft de-composing clay, porphyry, or grunstein, lo-cally termed rotten-stone, of argillaceous ironore, of marl, and of secondary lime-stone.*There does not appear to be any uniformsystem in the plans of nature as to the ar-rangement of these strata in regular alterna-tions; but sometimes one, sometimes more,interpose themselves between the seams of

* Much interesting information on the causes whichproduced the different formations in general will b*found in Cuvier’s Theory of the Earth.