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VOLCANOES OF THE LOWER OLD RED SANDSTONE book v 
3. The great centi'al basin of Scotland, which, for the sake of distinct- 
ness, I have called “Lake Caledonia,”' stretching between the Highlands 
and the Southern Uplands, from the east coast south-westwards across Arran 
and the south end of Cantire into Ireland as far as Lough Erne. Numerous 
distinct volcanic groups occur in this great basin, and tlieir volcanic 
liistory will ho discussed in detail in later chapters (see Map III.). 
4. The basin of the Cheviot Hills and Berwickshire, with these hills as 
the chief area, hut includiiig also other tracts, probably independent, which 
are cut off by the sea along tlie eastern coast of Berwickshire between St. 
Abb’s Head and Eyemoutli. 
5. The KiUarney tract, including tlie hills lying around Lough Guitane 
in the east of County Eerry. 
At the outset we may take note of a feature in the volcanic history 
of Britain, first prominently noticeable in the records of the Old Bed 
Sandstone, and becoming increasingly distinct during the rest of the long 
sequence of Palteozoic eruptions, namely, tlie persistence with which 
the vents have been opened in the valleys and have avoided the high 
grounds. I formerly dwelt on this relation, with reference to the Carbon- 
iferous volcanic phenomena,^ but the observation may be greatly extended. 
With regard to the Old Eed Sandstone of Central Scotland, though the 
lavas and tuffs that were discharged over the floor of the sheet of water 
which occupied that region gradually rose along the flanks of the northern 
and southern hills, yet it was on the lake-bottom and not among the hills 
that the orifices of eruption liroke forth. 
So far as I am aware, no undoubted vents of the age of the Lower Old 
lied Sandstone have been detected among the high grounds of the High- 
lands on the one hand, or among the Silurian uplands on the other, 
although a fringe of the lavas may be traced here and there along the base of 
the hills.® In some oases, doubtless, the position of the valleys may have 
been determined by lines of fault that might well serve as lines of relief along 
which volcanic vents would be opened. But in many instances it can be 
proved that, though the vents have risen in valleys and low grounds, they 
have not selected lines of fault visible at the surface, even when these 
existed in their neighbourhood. Any fissures up which the volcanic 
ejections made their way must have lain at great depths beneath the forma- 
tions that now form the surface rocks. 
* op. cit. ^ Trans. Roy. Sue. Edin. vol. x.\ix. (1879), ji. 454. 
* Certain remarkable necks of breccia have been detected by Mr. J. R. Dakyus rising 
through the schists at tlie u]iper end of Loch Lomond ; but there is not sufficient evidence to 
connect them with the volcanic series of the Lower Old Red Sandstone. Some of the younger 
granite bosses are not improbably to be referred to this volcanic series. The latest granites of the 
eastern Gramjiians, as already stated, have lately been found by Mr. Barrow cutting the band of 
2 )robably Lower Silurian strata along the southern border of the Highlands. Those of Galloway 
are younger than the Upper Silurian formations, which they invade, and older than the 
conglomerates of the Upiier Old Red Sandstone, which contain pebbles of them. These 
eruptive bosses will be further di.scns.sed in the sequel. 
