303 CARBONIFEROUS VOLCANOES OF THE LOTHIANS. 



green shale, covering red and white sandstone with conglomerate. 

 Fig. 64 shows portions of sandstone enclosed in the dolerite, which 

 grows redder towards the contact with the strata below. The aspect 

 of a portion of sandstone fairly enclosed in dolerite is seen in 

 fig. 64. 



The Basin of the Forth. Professor Archibald Geikie distin- 

 guishes six districts in the basin of the Firth of Forth which were 

 characterised by volcanic activity during the Carboniferous period. 

 These are i, Edinburgh; 2, Haddingtonshire ; 3, Linlithgowshire ; 

 4, Stirlingshire ; 5, West Fife ; 6, East Fife. 



Volcanoes of the Edinburgh District. In the Edinburgh dis- 

 trict the eruption began about the close of the Old Red Sandstone 

 period, when volcanic activity was general over the southern half of 

 Scotland. It formed the hills known as Arthur's Seat, Calton Hill, 

 and Craiglockhart Hill. In this district the earlier lavas are dole- 

 rites, and the later lavas are termed by Professor Geikie porphyrites. 

 Arthur's Seat is regarded as a prolongation of the old volcanic ridge 

 of the Pentland Hills, and is hardly two miles from the great vent on 

 the Braid Hills. The maximum thickness of the volcanic rocks at 

 Edinburgh is about 500 feet. 



Volcanoes of the Haddington District. The East Lothian or 

 Haddington district covers an area of about 65 square miles, and 

 includes the Garlton Hills, and most of the coast from Dirleton to 

 D unbar. The volcanic masses here reach a thickness of about 1500 

 feet, and consist largely of tuffs, interstratified with various sediment- 

 ary deposits. The oldest lavas are dark-red augitic rocks ; and the 

 later lavas are dull red, pink, grey, brown, yellow, and white porphy- 

 rites. On the coast, both east and west of North Berwick, many old 

 volcanic throats are seen, sometimes consisting of agglomerate, some- 

 times of basalt. North Berwick Law, the Bass Rock, the headland 

 of St. Baldred's Cradle, and Traprain Law, are cited by Professor 

 Geikie as examples of these necks ; and he observes that volcanic 

 action was prolonged in East Lothian after it had died out in the 

 Edinburgh district. 



Volcanoes of the Linlithgow District. In the West Lothian or 

 Linlithgow district there were many volcanic cones. The Binns Hill 

 of Linlithgow is one of these, consisting of fine green tuff, 350 feet 

 thick ; and S.W. from Binns the volcanic cones are grouped close 

 together, and threw out both ashes and dolerite. The thickness of 

 the volcanic rocks of the south of Linlithgow is about 2000 feet. 

 The intrusive sheets are of a later date, and Professor Geikie suggests 

 that some of them may be overflows from Tertiary dykes. 



Volcanoes of Stirling. The Stirlingshire district embraces the 

 Eastern prolongation of the Campsie Fells, which consists chiefly of 

 porphyrites and tuff's at the base of the carboniferous system. These 

 rocks are 1000 feet thick at Kilsyth, and thin away to the east, 

 so as to disappear about a mile north of Stirling, which is 13 miles 

 from Kilsyth. Subsequently thick sheets of dolerite extended from 

 Kilsyth round the base of Campsie Fells to beyond Stirling. They 



