OF THE TRAP-ROCKS OF SCOTLAND. 647 
felstone, intermingled with ashy layers. But it is possible that among the 
exposures of these rocks we have parts of several local eruptions, at all events, 
they do not exhibit the strongly marked features, and wide extent of the East 
Lothian ashes. 
After the period of the Burdiehouse limestone, volcanic rocks ceased to be 
ejected over the counties of Edinburgh and Haddington, while Linlithgowshire 
became eventually the seat of a vigorous and long continued volcanic activity. 
During the accumulation of the sandstones and shales which cover the Burdie- 
house limestone, showers of ash were of frequent occurrence, and these, along 
with ejections of greenstone, continued to increase in number up to the beginning 
of the Carboniferous Limestone. The range of hills from Bathgate to Borrow- 
stounness exhibits on a grand scale the character and extent of the trappean rocks 
with which that limestone is associated. Beds of limestone are there seen pass- 
ing into seams of ash, each full of the characteristic organisms of the series. 
Sheets of greenstone run horizontally among limestones, shales, and ash-beds; 
lenticular beds of limestone sometimes laminated with silica,* as in those of North 
Berwick, occur isolated among the ashes and basalts; while the whole series is _ 
traversed by dykes, and broken through by huge amorphous masses of green- 
stone that sweep up into rugged hills. It would be foreign to the purpose of the 
present paper to enter into the details of this most interesting region, I can only 
remark further, that when the lower part of the coal-field began to accumulate 
above the Carboniferous Limestone in this region, there existed a low volcanic 
bank which probably rose above the water-level and separated the coal swamps 
of Bathgate from those of Borrowstounness. From this bank, during the growth 
of the adjoining coal-fields, there issued several flows of greenstone and basalt, 
which, accumulating to a greater depth on the north side, now form enormous 
sheets in the coal-fields, and have to be sunk through for upwards of 400 feet, 
before the lower seams of the Borrowstounness coal-field are reached. The slow 
subsidence which had been going on all through the Carboniferous period, gradually 
brought down the volcanic islet beneath the sea-level, and eventually there 
formed over it and over the adjacent coal-fields, a thick series of sandstones and 
shales, with two seams of marine limestone. During these later changes, the 
old igneous forces had not become wholly dormant, as is sufficiently proved by 
several sheets of ash between the limestones and thick beds of greenstones above 
them. Another series of coal swamps, similar to the first, at length sprang up 
over the entombed limestones and traps, and stretched away to the east over the 
site of the old island. Yet these forests also eventually disappeared beneath a 
new succession of igneous ejections. How much further this history may be 
* A beautiful example occurs in the East Quarry, Kirkton, first noticed by Dr Hiszerr (Trans. 
Royal Soc., Edinburgh, vol. xiii. p. 278). See also “Geology of Edinburgh” (Memoirs, Geol. 
Survey). 
