The geology of the neighbourhoods of Flint, Mold, and Ruthin ...

The Glacial Deposits include two drifts of distinct origin, viz.,
that which travelled from the north over Lancashire and Cheshire,
and that which came from Welsh sources in the south-west. The
two meet along a line which partly follows the Welsh border,
but runs across the gentler hills of the Flintshire Coal-field.
Several examples of striated rock-surfaces have been recorded, in
all of which the striae point in the direction in which the Drift
associated with them has travelled. Vast numbers of boulders
also have been brought from the Snowdon and Arenig ranges
and dropped upon the western flanks and the tops of the Silurian
and Carboniferous ranges. One of the largest of these erratics is
24 feet long, and its visible portion can scarcely fall short of
300 tons in weight. The fact that the Drift was borne across
the outcrops of the various rocks, and nearly at right angles
to them, has led to even more variability in the nature of the
deposit than is usually observed.
The history of the River Dee is given in some detail, and the
valley of this river is shown to coincide with a pre-Glacial estuary
(or depression), filled with Glacial Drift. The upper part of the
river, however, follows a post-Glacial course through Holt,
Eccleston, and Chester, the pre-Glacial valley, now completely
choked with Drift, running past Dodleston and Rossett.
Chapter XIII. is devoted to a detailed account of the lead-
mines. The veins are separable into two sets of different direction,
contents, and age. The principal lead-bearing zones in the Lower
Carboniferous Rocks, and the various forms of " vein," " pipe," or
" flat," in which the ore occurs, are indicated.
The present Memoir has been edited and mainly written by
Mr. Strahan. Mr. De Ranee's contributions are as follows :
An account of the Lower Coal-Measures of Northop and Hawar-
den, on pp. 66, 67, 71 ; Chapter VII., pp. 72-99, on the Middle
Coal-Measures ; and notes on the Drift of his area, on pp. 132,
133,. 135, 139-144. Several also of the Colliery Sections, given
in Appendix L, were collected by him.
The determination of the fossils collected during the re-survey
was commenced by Mr. R. Etheridge, but completed by
Messrs. Sharman and Newton, who are responsible also for the
correction of the synonymy. The lists were submitted to Mr.
G. H. Morton also, who kindly noted some additions.
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