6,000 acres, is
undoubtedly the chief, although in some places it has suffered from
various disturbances, the principal of which occur in the neighbourhood
of Coleford, extending in a line from Worcester Lodge to Berry Hill, and
is marked on the surface by a succession of pools, named Howler's Well,
Leech Pool, Crabtree Pool, Hooper's Pool, and Hall's Pool. Mr. Buddle
describes the width as varying from 170 to 340 yards in the most defined
part, called by the colliers the "Horse," and the dislocations adjoining,
the "Lows." "It is not," he remarks, "what geologists term a _fault_, as
there is no accompanying dislocation of the adjoining strata. In its
underground character it is similar to those _washes_ or aqueous deposits
in many coal districts, but it differs from them in not being under the
bed of any river, nor in the bottom of a valley, nor does it show itself
at the surface." And he adds, "On considering the various phaenomena
presented by this fault, and the seam of coal on each side of it, we may
infer that it occupies the site of a lake which existed at the period of
the deposition of the High Delf seam, and that the carbonaceous matter
which formed the seam was accumulated while the water was deep and
tranquil. On the water being discharged from the lake, the 'Horse'
itself occupied the bed of the river, by which the complete drainage of
the lake was effected, and which washed the coal entirely out."

The same scientific observer records an extraordinary depression about
half a mile to the south-east, in the direction of the "Horse," and in
the same seam of coal, amounting to about twenty feet in depth, and of an
oval shape. Various other defects and disturbances in the Coleford High
Delf are detected from time to time by the new workings, especially in
those places where the surface is most uneven. Thus its outcrop at
Lydney is very imperfectly defined, and at Oakwood Mill the vein is
rendered worthless by a fault, whilst on each side of the Lydbrook valley
there is a contortion, by which it is thrown down in one instance seventy
yards, and in two others thirty yards each.

Such is the geological character of the conspicuous range of hills by
which the Dean Forest coal-field is bounded, especially on its north and
east sides. The following table gives their height in feet at certain
places above the sea:--

Feet.
Symmond's Rock 540
Buck St