the great Derbyshire Denudation. 245 
passing the edges of the lias limestones and clay strata, in our 
progress to the westward, from any of the south-eastern and 
eastern parts of England, we find on the surface marks of an 
immense stratum of red earth or marie, which basseting from 
under the lias clay and sand, seems once to have extended 
over all the remainder of the British islands, without being 
now any where covered by patches of upper strata,* much be- 
yond the continuous edge of the lias strata, abovementioned. 
Instead, however, of seeing the middle and all the western 
and northern parts of Britain covered by the same red strata, 
we find now, in this space, numerous local and many very 
large tracts of strata, surrounded by vertical and connected 
faults, and greatly lifted and tilted ; from the surface of 
which lifted tracts, the upper red earth, and vast and very 
unequal thicknesses of strata, that lay in regular succession 
below this red earth, have been denudated, “ abrupted,” or 
carried off, leaving thus, a great variety of what have been 
called coal-fields, or mineral-basins in which limited tracts, 
great and most important series of strata, are to be seen bas- 
seting (owing to the local denudations), of which the basset- 
edges, or continued endings, can no where be traced in these 
islands, as far as I can learn. Large tracts of the intervening 
spaces, between these denudated mineral basins, are still oc- 
cupied by the red marie, containing local strata of gypsum, 
rock-salt, sand, micaceous grit-stone, & c. &c. in its substance, 
or exposed by denudation ; and in others, local strata, or 
* Gravels, peat, & c. not being included in this term. 
f Of which a fine instance is described by Mr. Edward Martin, in the Philo- 
sophical Transactions for 1808, and of which the Forest of Dean presents a smaller, 
but similar instance. 
