52 PROCEEDINGS COTTESWOLD CLUB I90I 
stumps, the valleys broadened and shallowed, the general 
level was lowered, the streams meandered less rapidly to 
their mouth, and the physical features of the region 
approximated to the scenery which would be revealed, if 
the present Mesozoic envelope, from the Trias to the 
Oolites, were stripped away. 
The restoration of the pre-Mesozoic land surface of the 
Bristol area has been very clearly sketched by Prof. Lloyd 
Morgan." He points out that the old valley lines can often 
be traced, and gives in illustration some admirable 
examples occurring at Backwell. Here the “Dolomitic 
Conglomerate” runs like tongues into the Carboniferous — 
Limestone, filling in ancient valleys, which were converted 
into creeks, as the land sank beneath the waters of the 
Triassic lake. Another example was seen by the Club in 
their recent visit. The “ Dolomitic Conglomerate,” so 
well exposed in the Valley Road, fills in the bottom of a 
hollow in the Carboniferous Series, which rises into 
Clifton Down on one side and Durdham Down on the 
other. This “creek,” as Prof. Lloyd Morgan calls it, 
broadened and deepened towards the east; and the basal 
conglomerate was in that direction covered in by, or, per- 
haps, gave place to, the sediments of the Keuper series, 
which were deposited in a saline lake. 
In early Keuper times, subsidence set in. The waters 
of a great salt lake that spread over a large part of England 
entered the valleys on both the northern and southern 
sides of the Mendips, and crept slowly inwards, isolating 
mass after mass of elevated land, and converting the region 
into an archipelago. The first deposit to be laid down 
was the ‘“Dolomitic Conglomerate;” but some of the 
Keuper sandstones may be of about the same age. The 
origin of this conglomerate has given rise to some debate. 
1 Op. cit., pp. 31-35. 
