104 . REPORT—1850. 
any decided opinion on their bearing on the question of the mineral axis of the 
chain. On the whole of the evidence he however proposes (not without much doubt 
and hesitation) to separate the chain into the following groups, beginning with the 
lowest. 
8 II. Successive Groups in ascending order. 
(1.) A great group, always in a highly inclined position (and often so nearly per- 
pendicular that it is very difficult to know whether we are reading off the details in 
an ascending or a descending order), in which a pyritous alum-schist abounds, some- 
times so much that the coarse hard arenaceous beds become subordinate to it. In 
other places the schist becomes subordinate, indurated, and passes into a coarse 
slate or flagstone. The group ranges from the neighbourhood of Lockerby till it is 
succeeded by a superior group (north of Moffat) on the line of the railroad. It 
stretches into the high hills connected with Harter Fell, and into the ridges forming 
the water-shed of the Moffat water and the Yarrow. But its limits to the N.E. and 
S.W. are not ascertained. Through the alum-slates of this group (the Moffat group) 
are innumerable graptolites, well preserved and of many species. Its whole thick- 
ness is great, but the estimate is made difficult by the undulation. 
(2.) A great arenaceous group with bands of earthy flagstone and coarse slate, a 
part of which is well exposed, in numerous undulations, in the cuttings of the rail- 
road. The author thinks that this second great group passes into Peeblesshire and 
the upper parts of the valley of the Tweed, and that it thence extends to St. Abb’s 
Head. He wishes also (but not without hesitation, and on very inadequate evidence) 
to spread this group through a considerable part of the coast of the Mull of Gallo- 
way, and over the great promontory of Barrow Head. If this view be correct, the 
graptolite bands on the shores of Loch Ryan, and in other parts of Wigtownshire, 
must be referred to this group. He states, however, that this great group is provi- 
sional and very ill-defined, and that it may admit hereafter of new subdivisions and 
a more definite arrangement. 
After examining the valley of the Tweed, the author is very doubtful about the 
true place of the slate beds (with innumerable impressions of annelides) at Thorneyley 
on the Tweed, and of the slates of Grieston near Inverleithen (which contain many 
fine graptolites as well as impressions of fucoids and annelides) ; but he puts them 
provisionally in this second group. 
Two miles north of Peebles are some concretionary calcareous bands, associated 
with very coarse conglomerates of considerable thickness, and containing a few 
obscure traces of encrinites ; and about two miles further north are some brecciated 
beds with veins of quartz and cale-spar; and associated with them are slaty and 
more earthy bands, with concretions of rottenstone and calcareous veins. These 
beds are perhaps but a repetition of the conglomerates last noticed, for the whole 
system undulates and is very highly inclined. Traces of calcareous bands appear 
also on the hill above Stobo House further up the Tweed; and they finally are seen, 
along with a well-defined bed of limestone, at Wrae quarries, and in another quarry 
on the south bank of the Tweed, at Pretsell near Drumminelzier. 
The associated beds near these two old quarries are made up of very coarse grey- 
wacke, of shale with calcareous concretions, and of one subordinate bed of limestone, 
varying from ten or twelve to twenty feet in thickness. The calcareous shale with 
concretions is almost identical with similar shales above noticed to the north of 
Peebles; and a line drawn from the calcareous bands north of Peebles to Wrae and 
Pretsell quarries, is very nearly in the strike of the country. The author is anxious 
to put this calcareous range nearly on the same parallel with the limestones of the 
Stincher; while he admits that the physical and zoological evidence to prove this 
point is at present defective, especially as it is difficult to procure a good series of 
organic remains from this limestone. The author procured a few fossils from it; 
but a much better series has already been described by Professor Nicol. 
(3.) South Girvan group.—This is a very complicated group, and though spread 
over a wide surface by repeated undulations between Girvan and the valley of the 
Stincher, is of great thickness. The most remarkable beds are in the valley of the 
Stincher, and are composed of hard arenaceous bands sometimes passing into a very 
eoarse conglomerate, and associated with them are calcareous shale and masses of con- 
cretionary limestone of considerable thickness, which in the lower part of the Stincher 
