1852.] HARKNESS SILURIAN ROCKS OF SCOTLAND. 393 



4. On the Silurian Rocks of the South of Scotland, and 

 on the Gold Districts q/" Wanlockhead and the Lead Hills. 

 By R. Harkness, Esq. 



[Communicated by J. C. Moore, Esq., See. G.S.] 



[Abstract.] 



Mr. Harkness considers that the mineral axis of the system of 

 Silurian rocks in the south of Scotland is the syenitic mass of Criffel*. 

 The rocks lying next to the syenite are in a highly metamorphic 

 state, but wherever bedding can be traced, it is found that the strata 

 on the south side dip to the south, and on the north side to the north ; 

 which last northerly dip (or to speak more correctly N.N.W. dip) 

 continues with little exception to the northern margin of the Silurian 

 rocks. 



The lowest regularly stratified beds which can be observed on the 

 north of Criffel are near Woodside Hill, in the parish of New Abbey, 

 Kirkcudbrightshire, where the dip is N.E., but at no great distance 

 to the west of this the usual N.N.W. dip obtains. By following these 

 beds northward from Lochaber (where the syenite again occurs), an 

 ascending section is procured for six miles, the dip exceeding 70°. 

 The rocks consist of thick and thin greywacke sandstone (in contact 

 with the igneous rock), frequently showing the laminae of deposition, 

 succeeded by thin-bedded flaggy greywacke, resembling flinty slate. 

 Then follow in succession (at Longwood) greenish-grey, curved, lami- 

 nated beds, intersected by calcspar veins, — a series of chloritic shales, 

 interstratified with thin beds of fine-grained greywacke sandstone, — 

 shales, —and lastly sandstone and flaggy beds, which form the hills up 

 to the Nick of Bennerick. 



On the opposite side of the vale of the Nith, in the county of 

 Dumfries, a similar series of rocks occur, occupying a portion of the 

 parishes of Torthorwald and Tinwald. The author regards these rocks 

 as the base of the series dipping N.N.W. in the central portion of 

 Dumfriesshire, and, with the beds which lie to the south, as forming 

 the eastward continuation of the southern axis of this Silurian series. 

 Upon these, therefore, Mr. Harkness conceives the beds to rest which 

 were described in his former memoirf as occurring in the Glenkiln 

 Burn. They consist of thick- and thin-bedded greywacke, with An- 

 nelid-markings in its upper part, followed by drab-coloured shales and 

 anthracite, — then shales with Graptolites, — a great thickness of grey- 

 wacke sandstone, — and lastly grey, green, and purple shales, the last 

 sometimes showing ripple-marks and Annelid-markings. These 

 coloured shales are exposed on the Garrell, Glenkiln, and Newlands 

 Burns ; and, by following the line of strike from the Newlands Burn 

 westward (S.W.), the shales with Annelids are again met with at 

 Parton slate-quarry, about six miles north of Castle Douglas and 

 about twenty miles from Newlands. The shales are here much indu- 

 rated, and there is a local disturbance of the dip. Succeeding these 

 shales are greywacke sandstones, which are seen at Parton, and also 



* See also Quart. Journ. Geol, Soc. vol. vii. p. 56. f Loc. cit. p. 49. 



