Carboniferous Period in East Scotland. 243 
This type of sedimentation ceases in Liddisdale where it is succeeded by the 
Fell Sandstones, a group showing a rythmical alternation of massive sand- 
stones, variegated clays, and coal seams, some of. which are worked in the 
Plashetts Coal-field on the English side of the Border. 
VULCANICITY DURING CEMENTSTONE TIMES. 
The Upper Old Red volcanoes of the Merse and Liddisdale had become 
extinct before the close of that period. Farther to the north in East Lothian 
volcanic action broke out in Cementstone time, continued throughout the 
rest of that period and did not cease till the greater part of the succeeding 
group was deposited. Their ejectementa now form the Garleton Hills. 
In Midlothian during this period, the Arthur’s Seat volcano ran through 
all its phases, became extinct, and was buried up under the accumulating 
sediments of the group, and also the lavas and tuffs of smaller volcanoes that 
are now represented by Craiglockhart and Corston Hills. In the Campsie 
region volcanoes were almost continuously active throughout the whole 
period, and even on till Carboniferous Limestone time, giving rise to the 
great volcanic plateau which stretches from the Campsie and Kilpatrick Fells 
across the Clyde, there forming the Renfrewshire Heights. They also make 
up the great tableland separating the Clyde valley from the Ayrshire Low- 
lands. The eastward extension of the plateau is shown in the Cult Hills of 
Fife where it rises from under the Stirling and Clackmannan Coal-fields. 
(6) THE OIL-SHALE Group. 
The oil-shale type of sedimentation seems to have taken place within a 
very restricted area over what is now practically co-extensive with Mid and 
West Lothians and a small adjacent part of Fife. To the west, the area was 
held in by the accumulating volcanic rocks of the plateaus of Stirling, 
Dumbarton, and Lanarkshire, which there entirely replace the oil-shales. 
The remnant of the Southern Uplands that still stood above water, hemmed 
in these sediments towards the south-west, while, to the east and south lay 
the open sea, which periodically invaded the area as the land went down by 
small step-like movements. Estuarine conditions prevailed for the most 
part, but lagoons must have formed which were not often subjected to 
desiccation like those in which the cementstones were deposited. But there 
is evidence to show that they were sometimes so much flushed by rain as to 
become freshwater lakes. This seems to argue that a complete change of 
climate had been brought about by great earth movements somewhere outside 
the region at present under consideration. 
VOL, XIX. R 
