150 
SILURIA. 
[Chap. VIII. 
Trap and porphyry, *. 
Mountain-limestone and 
Coal-formation, g. 
Old Eed Conglomerate,/. 
B 
O 
HErnton beds. 
a 
f 
i 
Thornielee elates. 
Tweed. 
G-rieston slates. 
Felspar-porphyries. 
Wrae limestone. 
Old Eed Sandstone,/. 
Carboniferous Limestone 
and coal-fields, g. 
Trap and porphyry. 
ii 
inland masses of the Scottish grey- 
wacke, we have now reached that 
starting-point. When traversing 
the tract between Dumfries and 
Moffat, in 1850, it occurred to me 
that the dull reddish or purple 
sandstone and schist to the north 
of the former town would prove to 
be the true axis of the South of 
Scotland f; for this mass (similar 
to much of the hard rock of St. 
Abb's Head) evidently throws off 
anthracitic schists, with Grapto- 
lites, both to the south and to the 
north. Professor Harkness estab- 
lished this order, after my visit, 
by detailed sections in that parallel, 
ranging by the Dryfe Water J. The 
same author has also communicated 
a memoir to the Geological Society, 
wherein he traces this axial line 
from the E.IST.E. in Eoxburghshire 
to the W.S.W. across Dumfries- 
shire, where, covered for a space 
by the red sandstone (Permian) of 
Corncockle and Dumfries, it seems 
to trend to the granitic mountain 
called the Criffel, in Kirkcudbright- 
shire §. 
Professor Nicol, who first opened 
out the proofs, both physical and 
fossiliferous, that the South Scottish 
Hills are really Silurian, has satis- 
fied himself that this true axis of 
the oldest and as yet unfossilife- 
rous rock ranges by Teviotdale ||. 
Proceeding from that centre, he 
prepared the annexed general sec- 
tion, which (minor flexures being 
omitted) exhibits a short ascending 
t Quart. Journ. Geol. Soc. vol. vii. p. 162. 
j Ibid. vol. vii. p. 52, and vol. viii. p. 393. 
% Ibid. vol. xii. \i. 238. 
|| Meeting of British Association, Belfast, 1852. 
