ERRATICS NEAR CHICHESTER. 
181 
since we must allow time, first for its sinking, and then for 
its re-elevation. 
The height reached by these fossil shells on Moel Tryfaen 
is no less than 1300 feet—a most important fact when we 
consider how very few instances we have on record beyond 
the limits of Wales, whether in Europe or North America, 
of marine shells having been found in glacial drift at half 
the height above indicated. A marine molluscous fauna, 
however, agreeing in character with that of Moel Tryfaen, 
and comprising as many species, has been found in drift at 
Macclesfield and other places in central England, sometimes 
reaching an elevation of 1200 feet. 
Professor Ramsay* estimated the probable amount of sub¬ 
mergence during some part of the glacial period at about 
2300 feet; for he was unable to distinguish the superficial 
sands and gravel which reached that high elevation from 
the drift which, at Moel Tryfaen and at lower points, con¬ 
tains shells of living species. The evidence of the marine 
origin of the highest drift is no doubt inconclusive in the 
absence of shells, so great is the resemblance of the gravel 
and sand of a sea beach and of a river’s bed, when organic 
remains are wanting ; but, on the other hand, when we con¬ 
sider the general rarity of shells in drift which we know to 
be of marine origin, we can not suppose that, in the shelly 
sands of Moel Tryfaen, we have hit upon the exact upper¬ 
most limit of marine deposition, or, in other words, a precise 
measure of the submergence of the land beneath the sea 
during the glacial period. 
We are gradually obtaining proofs of the larger part of 
England, north of a line drawn from the mouth of the Thames 
to the Bristol Channel, having been under the sea and trav¬ 
ersed by floating ice since the commencement of the glacial 
epoch. Among recent observations illustrative of this point, 
I may allude to the discovery, by Mr. J. F. Bateman, near 
Blackpool, in Lancashire, fifty miles from the sea, and at the 
height of 568 feet above its level, of till containing rounded 
and angular stones and marine shells, such as Turritella com¬ 
munis^ Purpura lapillus^ Cardium edule^ and others, among 
which Trophon clathratum {=Pusus Pamffius)^ though still 
surviving in North British seas, indicates a cold climate. 
Erratics near Chichester, —The most southern memorials 
of ice-action and of a Post-pliocene fauna in Great Britain is 
on the coast of the county of Sussex, about 25 miles west of 
Brighton, and 15 south of Chichester. Amarine deposit ex¬ 
posed between high and low tide occurs on both sides of the 
* Quart. Geol. Journ., 1852, vol. viii., p. 372. 
