Chap. VIII.] SILUEIAN ROCKS OP SCOTLAND. 149 
of Sedgwick, Moore, Cunningham, Stevenson, Harkness, the officers of the 
Geological Survey (particularly Mr. Geikie), and myself, have brought the 
Scottish masses into a distinct comparison with their true types. 
Silurian rocks, and especially those of the lower part of the series, are now 
known to occupy a very large region in the South of Scotland. Ranging 
on the whole from E.N.E. to AV.S.W V they appear in considerable masses 
in Berwickshire and Roxburghshire, and thence spread out in still larger 
areas over the counties of Selkirk, Peebles, Dumfries, Kirkcudbright, Gal- 
loway, Wigton, and Ayr. In short, they constitute, on the whole, the 
undulating moory hills which, from their prevalent wildness of aspect, 
have been called the South Highlands (or Southern Uplands). Subjected, 
as they have been, to numerous eruptions of granite, syenite, porphyry, 
greenstone, and other igneous rocks, some of these ancient schists have 
long been known to geologists for the remarkable curvatures they exhibit 
in the sea-cliffs of Berwickshire. A drawing is subjoined which repre- 
sents such flexures and breaks, as seen in the cove called Petticoe "Wick, 
near St. Abb's Head*. 
View op the Cliffs near St. Abb's Head. 
(From a Sketch by Sir A. Alison, Bart.) 
As numerous similar contortions are visible also in the western prolon- 
gation of the same great series to the coast of Wigton and Ayr, we ought 
to be cautious in determining sections across the interior portions of a re- 
gion where the surface of the round and undulating hills is obscured by 
moss, heath, and bog, and where exposures of the bare rock are rarely to 
be met with. 
Difficult, however, as it has been to fix upon the oldest portion of these 
* The woodcut is taken from one of several companions. This coast has since been mapped and 
rapid, clever sketches made in my note-book, in described in detail by Mr. G-eikie, ' Memoir on the 
the autumn of 1833, by Sir Archibald Alison, the Geology of Eastern Berwickshire ' (Mem. G-eol. 
historian, from a boat in which Sir John Hall of Surv. 1864, p. 6 et seq.). 
Dunglass and Professor Sedgwick were also my 
