456 Lapworth Sf Wilson — Silurian Rocks of Roxburgh ^ Selkirk. 



V. — On the Silurian Eocks of the Counties of Eoxburgh 

 AND Selkirk.^ 



By C. Lapworth and Jas. Wilson. 



FOR the last three summers we have devoted the greater part of 

 our leisure time to the examination of the Silurian Rocks that lie 

 more immediately between the Moorfoot Hills and the English border. 

 Our investigations have been attended with a fair amount of success, 

 and we thought that a short summary of what we have accomplished 

 would not be wholly uninteresting to the Geological Section. As 

 these old Silurian strata of the South of Scotland have only been 

 once alluded to in the papers already read at the Meeting — namely, 

 by the Chairman in his eloquent address — we may be pardoned if we 

 say a few preliminary words concerning them. 



These Silurians fill up almost the whole extent of Scotland that 

 lies to the south of the great central Carboniferous basin, and stretch 

 uninterruptedly from sea to sea, forming the largest area of unaltered 

 Silurian in the British Isles. The investigation of these rocks is at- 

 tended by almost insurmountable difSculties. In the district to be 

 described, the beds are folded and contorted in the most remarkable 

 manner, so that it is possible to walk for a mile across the dip where 

 the rocks are well exposed — as, for instance, in the beautiful glen of 

 the Yarrow, below the old peel of Newark — without ascending or 

 descending more than three hundred feet in the order of the beds, 

 and this, when the rocks are pitching at angles, varying from 80° to 

 the perpendicular. All these old strata have pretty much the same 

 lithological character throughout ; there are no limestones, scarcely 

 any conglomerates, and only one constant easily recognizable bed 

 among them ; and not only so, but previous to our labours, scarcely 

 any fossils had been discovered, except in a few isolated spots, from 

 which the age of these ancient sediments could be determined. With 

 all these difficulties in the way of their investigation, there can be no 

 wonder that these rocks have been neglected by geologists for the 

 younger and more promising formations, and that the Government 

 Geological Survey have been forced to colour all the beds of this 

 district already surveyed of a uniform purple tint. Nevertheless, 

 much has already been done, and well, and the well-known names 

 of Murchison, Nicol, Harkness, and Geikie, are only the first of a 

 long array of those who have laboured long and devotedly among 

 them. 



Small portions of the district more particularly examined by us 

 were described by Professor Nicol, in papers read before the Geolo- 

 gical Society of London, and published in volumes iv. and vi. of 

 their journal. 



He discovered Oraptolites Griestonensis (Nicol), G. Sedgwiclcii 

 (M'Coy), and G. priodon (Brown) in the Grieston Slates, and a 

 peculiar form he called Graptolites laxa in the Thornilee Quarry. 

 He mentioned the fact of dark schists with carbonaceous markings 



^ Kead before Section C of the British Association, Edinburgh. 



