Io8 PKOCEEDINGS OF THE GEOLOGICAL SOCIETT. 



(2) Some fifty miles to the east of this main volcanic district, 

 and entirely independent of it, lies the plateau of the Garlton Hills 

 in East Lothian, which, as its limits towards the east and north 

 have been reduced by denudation, and towards the west are hidden 

 under the Carboniferous Limestone series of Haddington, covers 

 now an area of not more than about sixty square miles. That the 

 eruptions from this area did not extend far to the west or north is 

 shown by the absence of all trace of them among the Lower Car- 

 boniferous rocks of Midlothian and Pife. Small though the plateau 

 is, it possesses much interest from the remarkable variety of petro- 

 graphical character in its lavas, from the size and composition of its 

 necks, and from the picturesque coast-line where its details have 

 been admirably dissected by the waves. In many respects it 

 stands by itself as an exception to the general type of the other 

 plateaux. 



(3) South-westwards, from Edinburgh, on the stratigraphical 

 horizon of the volcanic plateaux, a band of lavas and tuiFs, which 

 can be followed into Lanarkshire, but is not continuously visible, 

 possibly indicates the outcrop of the mere edge of a distinct but 

 buried plateau, the main part of which may lie under the Car- 

 boniferous rocks that stretch away towards the west. 



(4) Another and entirely disconnected plateau occurs in the 

 broad plain or Merse of Berwickshire. The northern limit of its 

 volcanic tuff may be found in the Biver Whiteadder above Duns, 

 whence the erupted materials rapidly widen and thicken towards 

 the south-west by Stitchell and Kelso until they die out against 

 the flanks of the Cheviot Hills. The eastern extension of this 

 volcanic area is lost beneath the Cement-stone group which covers 

 the broad Merse down to the sea. Its western boundary must 

 once have reached far beyond its present limits, for the low 

 Silurian country in that direction is dotted over with scattered 

 vents to a distance of several miles from the bedded lavas. This 

 extensive denudation has thus cleared away the erupted materials 

 and exposed the volcanic pipes over many square miles of country. 



(5) The last plateau, which I may call that of the Solway 

 basin, though its present visible eastern limits approach those 

 reached by the lavas from the Berwickshire area, was quite distinct, 

 and had its chief vents at some distance towards the south-west. 

 On the north-western flanks of the Cheviot Hills the Upper Old Eed 

 Sandstone is overlain by the lowest Carboniferous strata without 

 the intercalation of any volcanic zone, so that there must have 



