248 
SILURIA. 
[Chap. XI. 
as in the parts of England just mentioned, the group is more grandly dis- j 
played in the North-eastern Highlands than in any other part of Europe. 
Old Red Sandstone of Scotland. — Dwindling away from its copious de- 
velopment in Brecon, Hereford, and Salop, the Old Red Sandstone of the 
North of England is, as before stated, little more than a single band of coarse 
conglomerate, a small skirting mass, lying between the Silurian and Car- 
boniferous deposits of the Lake-district of Cumberland. This single mem- 
ber, of a series so copious elsewhere, there reposes on the truncated edges » 
of the older slaty rocks. 
In Scotland, however, the deposits of this age are more expanded than j 
in any part of England and Ireland. Ever since the admirable writings 
of Hugh Miller, and his description of its fossil Eishes, the Old Eed Sand- 
stone has been a name so popular that in North Britain, at least, my 
countrymen, although they admit the truthfulness of the identification of 
the group with the < Devonian ' of other countries, have naturally clung to 
the long cherished term. 
In the following sketch of the development of the Scottish Old Red 
Sandstone, I commence with a brief account of it in the countries lying 
between the English border and the great valley of the Eorth and Clyde. 
Now, although I have myself examined strata of this age at various points 
within this region during bygone years, I am too happy to avail myself 
of the fresh light which has been thrown upon that southern region since 
the last edition of this work by my colleague Mr. Geikie, who has fur- 
nished me with the following valuable notice : — 
" In the southern half of Scotland, between the Grampians and the Che- 
viots, the Old Red Sandstone is abundantly developed. Recent observa- 
tions lead me to regard it as divisible there into three groups, as under : — 
" a. Upper red and yellow Sandstones and Conglomerates, with 
Holoptychius, Pamphractus, Glyptopomus, Cyclopteris Hibernica, &c. 
b. Middle series of green, grey, and reddish Sandstones, Elagstones, and 
Conglomerates, with a copious intermingling of contemporaneous vol- 
canic rocks : Pterichthys major in the upper part. c. Lower red, 
chocolate, and grey Sandstones, Elagstones, and Conglomerates, some- 
times with enormous intercalated masses of trappean rocks : Cephalaspis 
Lyellii and Pterygotus Anglicus. 
" c. The lower group in the Lesmahago district is found passing down 
conformably into the Upper Silurian shales, as already described by Sir R. 
Murchison {ante, p. 160); and the same passage appears to be traceable in 
the Pentland Hills (b, in the following diagram). This group attains a great 
development between the basin of the Clyde at Lanark and the Ayrshire 
Coal-fields*, reaching a thickness of perhaps 7000 feet. It is well seen at 
the Falls of Clyde, where it consists of dark chocolate-coloured sandstones. 
Round Tinto it contains masses of trappean conglomerate, which, along with 
* See Quart. J ourn, Geol. Soc. vol, xvi. p, 312, 
