CHAP. XXIV 
THE CL YDE PL A TEA U 
369 
of Cumbrae to the southern end of Bute, and thence by the east of Arran to 
Campbeltown in Cantyre. Its visible remnants thus extend for niore than 
100 miles from north-east to south-west, with a width of some thirty-hve 
miles in the broadest part. We shall probably not exaggerate if we estimate 
the original extent of this great volcanic area as not less than between ^000 
and 3000 square miles. i ■ n 
It is in this tract that the phenomena of the plateaux are most admirably 
displayed. Kanges of lofty escarpments reveal the succession of the several 
eruptions, and the lower ground in front of these escarpments presents to us, 
as the result of stupendous denudation, many of the vents from which the 
materials of the plateau were ejected, while in the western portion of the area 
admirable coast-sections lay bare to view the minutest details of structure. 
It will be seen from the map (No. IV.), that the Clyde plateau extends 111 
a general north-east and south-west direction. It is inclined on the whole ■ 
towards the east, where, when not interrupted by faults, its highest lavas 
and tuffs may be seen to pass under the Carboniferous Limestone series. 
Its greatest elevations are tlms towards its escarpment, which, commencing 
above the plains of the North a little to the west of Stirling, extends as a 
striking feature to the Clyde above Dumbarton. On the south side of the 
f-reat estuary the escarpment again stretches in a noble range of terraced 
slopes for many miles into Ayrshire. It is well developed 111 the Litt e 
Cumbrae Island (Fig. 107), ami in the south of Bute, where its successive 
platforms of lava mount in terraces and green slopes above the Firth. Lven 
as far as the 'southern coast of Cantyre the characteristic plateau scenery 
reappears in the outliers which there cap the hills and descend the slopes 
(Fig. 108). . . , „ 
Wliile the escarpment side of this plateau is comparatively uufaulted, so 
that the order of succession of the lavas and their superposition in the sedi- 
mentary rocks can be distinctly seen, the eastern or dip side is almost 
everywhere dislocated. Innumerable local ruptures have taken place, 
allowing the limestone series to subside, and giving to the margin of the 
volcanic area a remarkably notched appearance. To the effects of tiis 
faulting may be attributed the way in which the plateau has been separatee 
into detached blocks with intervening younger strata. Thus a compDx 
series of dislocations brings in a long strip of Carboniferous Limestone w 11 c 1 
extends from Johnston to Ardrossan, while another series lets in tie imes one 
that runs from Barrhead to near Dairy. In each of these instances, the 
1 This plateau ie repre.sented in Sheei. 12, 21, 29, 30, 31 and 39 of the Geological Survey and is 
described in the accompanying Memoirs as far as published. The eastern pait of the Campsie 
Hills was surveyed by Mr. B. N. Peach, the western part by Mr. R. L. Jack, who also mapped 
the rest of the jilateau to the Clyde, and a portion of the high ground of Renfrewshire and Ayr- 
shire ; the rest of the area, south to Ardrossan, was surveyed by myself. The tract from Stewarton 
to Sriathavon was surveyed by Mr. .Tames Geikie, the Ciimbraes and Bute by Mr \\ Gunn, and 
southern Cantyre by Mr.,R. G. Symes. The Campsie Hills have been partly described by Mr. John 
Youno- in the first volume of the Transactions of tlie Glasgow Geological Socictn. 1 he ooeurience 
of plants in the tuffs of the east coast of Arran was discovered by Mr. E. Wunsch. The Campbel- 
town igneous rocks were described by J. Nieol, Quart. Jotmi. Gcol. Soc. viii. (l8o‘ ), p. ■ 
also J. Bryoels Arran and Clydesdale. ^ 
VOL. I 
