252 . Prot. Sedgwick on the Geological Structure 



the coast of the Mull of Galloway, and over the great pro- 

 montory of Barrow Head. If this view be correct, the grap- 

 tolite bands on the shores of Loch Ryan, and in other parts 

 of Wigtonshire, must be referred to this group. He states, 

 however, that this great group is provisional, 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 Innerleithen (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 calcar- 

 eous bands, associated with very coarse conglomerates of 

 considerable thickness, and containing a few obscure traces 

 of encrinites ; and about two miles farther north are some 

 brecciated beds with veins of quartz and calc spar ; and asso- 

 ciated with them are slaty and more earthy bands, with con- 

 cretions of rotten stone 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 hills above 

 Stobo House farther 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 Drummelzier. 



The associated beds near these two old quarries are made 

 up of very coarse greywacke, of shale with calcareous concre- 

 tions, 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 draw^n 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 diflicult to 



