584 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



chison has proved the correctness of his hypothesis, and at length 

 established the geology of the north of Scotland on a sonnd basis. 



Old Red Sandstone or Devonian Rocks of the North Coast of Scotland. 

 —I have just shown in the preceding section that they overlie and 

 follow in true geological sequence the central deposit of gneiss, and, 

 as their upper beds are to be found in the red sandstones of Dunnet 

 Head and of Duncansby Head, overlooking the German Ocean, they 

 must therefore be regarded as at the top of the geological scale on 

 the north coast of Scotland. I look upon the sandstones and con- 

 glomerates in the neighbourhood of Tongue as belonging to this 

 system, and I doubt not that futui'e explorations may bring to light 

 additional patches of sandstone on the hills near the north coast of 

 Sutherland, which may connect the Tongue sandstones vdth those of 

 Strathy and Portskerray. It has long been an interesting question 

 amongst geologists, at what period did the denudation of the sand- 

 stones and conglomerates of the North Highlands take place ? — was 

 it at the glacial period, when the boulder- clays of Caithness and the 

 north-east of Scotland were deposited ? A careful examination and 

 mapping- out of the remains of the sandstones and conglomerates on 

 the hills of Sutherland and Ross might do much to settle the ques- 

 tion and should be kept in mind by our younger geologists. 



Instead of giving a detailed description of the Devonian rocks of 

 this district, I must in strict justice rather refer to the admirable 

 memoir of Messrs. Sedgmck and Murchison on this subject laid 

 before the Society thirty years ago, for nothing can surpass the 

 faithfulness and beauty of their descriptions or the comprehensive 

 and satisfactory manner in which they draw their conclusions ; in 

 fine, it is so copious and correct, that, with the addition of a few 

 notes explanatory of the discoveries of Professor Traill and Hugh 

 Miller, Mr. Dick of Thurso, and Messrs. Cleghorn and Peach, of 

 Wick, regarding the boulder- clay and the organic remains of the 

 formation generally, it would serve as an excellent and most able re- 

 port on the geology of Caithness, so far as known at the present day. 



Concluding RemarJcs. — In the foregoing short descriptions of the 

 various formations, I have pointed out the order of superposition of 

 each forraation as we came along in our narration from the west to 

 the east coast, and I think it has been distinctly proved that the 

 gneiss of Cape Wrath lies at the foundation of the system, followed 

 by the sandstone of Cape Wrath, quartzites and limestones of Duir- 

 ness and of Ltch ErriboU, central gneiss of the North Highlands, and 

 Devonian rocks extending from Strathy to Duncansby Head, at 

 the top of the system, on the German Ocean ; and while we are glad 

 that the leading points of the geology of this interesting region have 

 at length been satisfactorily ascertained, we should remember that 

 much still remains to be done in its palaeontology, — the Duirness 

 limestone and the fossiliferous beds of Caithness are not half explored, 

 and laurels are still to be gained by successful labourers in those 

 localities. 



