238 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Mar. 5, 



Lastly, Dr. Rubidge supplied some remarks on the geology of the 

 copper-district of Namaqualand and bordering countries. Granitic 

 rocks of several varieties occur, together with gneiss, mica- schist, and 

 talc-schist. The gneiss strikes 5° to 20° S. of W., and dips alter- 

 nately N. and S. ; one dip continuing for many miles. On the hills 

 the gneiss and schists are covered by horizontal sandstones, which 

 appear to be the same as the sandstone of Table Mountain, and con- 

 tinuous with it. 



The copper is found in fissures of the gneiss, where the latter is 

 locally disturbed in its dip, the strike remaining unaltered ; that is, 

 along anticlinal and synclinal folds or axes ; also in fissures extending 

 nearly in the direction of the magnetic meridian, and in crevices 

 between masses of rock, with no veinstone or gangue : the oxides 

 and silicates often appear to be infiltered into the rock-mass. The 

 ores most common are red and black oxides, green and blue silicates, 

 purple and yellow sulphurets, and a few carbonates. Granitic rocks 

 are often found in the axes above referred to. 



2. On the Lowest Sedimentary Rocks of the South of Scot- 

 land. By R. Harkness, Esq., F.G.S., Professor of Geology 

 and Mineralogy, Queen's College, Cork. 



It is stated in Sir Roderick Murchison's ' Siluria,' page 151, on my 

 authority, that the axis of the Silurians of the South of Scotland 

 ranges in the direction of the Dryfe Water. In order to satisfy my- 

 self as to the exact position of this axis, and of the deposits with 

 which it is more immediately associated, I examined in detail, during 

 last summer, that portion of the county of Dumfries where this axis 

 occurs. Its position in the adjoining county of Roxburgh is laid 

 down by Professor Nicol as near the course of the River Teviot*. 

 West from Hawick, however, it appears to leave this stream, and 

 follows nearly the direction of the Borthwick Water. 



In the high mountainous district which separates Roxburghshire 

 from Dumfriesshire, the exact position of the axis is difficult to de- 

 termine owing to the want of good sections, and from the thick cover- 

 ing of soil which here invests the mountains. Even in the course of 

 the River Esk, in Dumfriesshire, which intersects the country almost 

 at right angles to the strike of the strata (and in which, on looking 

 at the map, we should naturally expect to find good sections, and 

 the axis well exhibited), the solid rock is not well exposed in con- 

 sequence of the gravelly nature of the bed of this river. Yet through 

 the whole course of this stream, from Skipper's Bridge, about a mile 

 south of Langholm, where the Silurians first make their appearance, 

 to near Eskdale-muir Bridge, wherever we have the strata exposed, 

 these possess (when not perpendicular) the prevailing south dips 

 which mark the deposits forming the Silurians on the south side of 

 the axis. 



* ' Siluria,' page 152. 



