THE WEST OF ENGLAND AND EAST OF WALES. 449 
must have sent off fragments to Strethill, near Ironbridge*. It is 
well known that Charnwood Forest and Mount Sorrel have dispersed 
boulders in many directions—according to Mr. Lucy, F.G.8., as far 
as the Cotswold hills, and—according to Dr. Buckland, as far south 
as Abingdon and as far 8.S.E. as Dunstable. Should it be surmised 
that these local dispersions were effected by floating ice after the 
disappearance of the great ice-sheet, it may be replied that many 
of them have been found imbedded in a Boulder-clay which is 
probably a continuation of the Great Chalky Clay of the eastern 
counties. 
VIII. Posrrtons or BouLpDERS RELATIVELY TO THE Matrix oF 
DriIrt-DEposIts. 
1. Along the Valley of the Dee §c.—Between Bala Lake and Ruabon 
the transition from high- to low-level drift, on the same horizon, may 
be clearly seen. Filling up abrupt hollows there is a clay or loam, 
with boulders, which may have been left by the passage of land-ice. 
Above this deposit (where it is present), or resting on the rock- 
surface, there is a heterogeneous accumulation consisting of clay, loam, 
and unstratified subangular gravel, the whole interspersed with 
boulders, which, however, are most frequently seen towards the 
base or top of the formation. This boulder-drift thins out upwards 
on the hill-sides, where it graduates into a chip-and-splinter drift, 
with an occasional rounded stone, and large boulders which (where 
there is little or no drift-matrix) appear on the surface. About 
Corwen very fine sand with drifted coal (drifted up the valley of 
the Dee in the teeth of the boulder-dispersion) either comes over 
this boulder-drift or is interstratified with it. Between Corwen and 
Ruabon, by way of Llangollen, there is generally but little clay in 
the boulder-drift, and it is often seen to graduate downward into 
angular débris and broken-up rock im situ. About Ruabon it 
graduates horizontally into the lowest drift of the plain of Denbigh- 
shire and Shropshire, which is either a Boulder-gravel or a Boulder- 
clay, and the latter graduates northward into the Lower Boulder-clay 
of the Cheshire and Lancashire plain. Considering the difference of 
level, the age of these deposits cannot be the same, though they are 
horizontally continuoust. In the Denbighshire plain the Arenig 
boulders are principally found in the lowest gravel, or gravelly 
loam, clay, and sand; but in the neighbourhood of the mountains 
they are not absent from the overlying finer gravel and sand. Ata 
distance from the mountains, in the low-lying fine gravel and sand of 
Cheshire and Lancashire, boulders are never to be seen. It would 
be difficult to ascertain whether the Arenig boulders found in the 
drift-deposits of the Denbighshire plain bordering the Welsh moun- 
tains were dispersed during the sinking or rising of the land, or 
both. 
* Mr. Percival has found fragments from the Wrekin area as far S.E. as 
Moseley near Birmingham, and nearly as far H. as Lichfield. 
+ For this yery convenient phrase I am indebted to Mr. 8. V. Wood, jun, 
E.G.S. 
212 
