Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/219

 stone with the intermedium (perhaps) of the coal measures, the other abutting against the broken edges of the strata of limestone at the base of its escarpment. Perhaps there may be found some valley of denudation connecting together the two plains, which being itself filled with red marl of the same description, there may be an uninterrupted bed of marl through the valley from one plain to the other.

The determining of this question would be of some importance as a matter of speculation, and of some practical consequence to the coal viewer. Those who consider the red marl as one of a complete series of beds succeeding one another in a uniform order, will in every case expect to find the coal measures on sinking through the red marl. If on the contrary we suppose denudatory or other disturbing causes to have been in action previously to the deposition of the red marl, we might expect to find the red marl immediately incumbent upon any rock from the coal measures to the granite inclusive, just as the alluvial beds in which the bones of elephants are found in consequence of previous denudation are discovered resting either upon the blue clay of London, upon the Oxford oolite, or any other bed: and on this view of the subject the red marl will no more be an indication of coal than of any other member of the lower strata.