316 PKOCEEDINGS OF THE GEOLOGICAL SOCIETr. [June 9, 



Kil-Donnan itself there stands out a wall of hard, whitish, brittle 

 quartz-rock, which forms the Scarabin Hills*. These, which I have 

 visited at intervals, suggested to me the idea that they were the re- 

 sult of intense metamorphism of Lower Silurian rocks. 



When I first heard of the Sutherland discovery, in January last, I 

 wrote to my friend Mr. Joass, urging him to examine the tract ; 

 for I knew that he combined the powers of a good geological observer 

 with those of a skilful artist, and also that, through his residence 

 at Golspie in the neighbourhood, he would be enabled to give us a 

 better account of the real nature of the deposit than any casual 

 visitor. I then found that he had already anticipated my wishes to 

 a great extent ; and since then, being encouraged by the Duke of 

 Sutherland, the liberal-minded proprietor of the grounds, and His 

 Grace's chief agent, Mr. G. Loch, M.P., he has greatly extended his 

 acquaintance with the localities. As, fortunately, he has now come 

 to London to tell us his own tale, I have no doubt that my associates 

 will derive a very clear view of all the relations of these auriferous 

 deposits — the more so as the map and sections which he has prepared 

 are worthy of all commendation, and fully explain the detailed and 

 complicated relations of the different rock-masses, with which I was 

 unacquainted. 



A note or two embodying my opinion as to the sources from 

 which the Sutherland gold- detritus has been derived may not be 

 out of place. Seeing, as above explained, that the transport of the 

 great mass of the auriferous materials in question has in all proba- 

 bility been from W.N.W. to E.S.E., we have now to consider the 

 composition of the successive rock-formations which present them- 

 selves as the observer proceeds from the west to the east coast, in 

 order to form an opinion as to which of the parent rocks may most 

 probably have furnished the gold-detritus. 



1. The Laurentian or fundamental gneiss may be excluded from 

 our consideration, not only from its composition and the absence in 

 it of anything like auriferous quartz-veins, but also because it forms 

 for the most part low buttresses only on the west coast, and scarcely 

 anywhere rises to the height of the mountain watershed. 



2. The Cambrian rocks -are also excluded from our reasoning, for 

 they are simply hard sandstones, grits, and conglomerates, which, 

 clearly exposed in mountain-masses, never exhibit any metalliferous 

 veins, and scarcely ever show any signs of metamorphism. They are 

 entirely discordant to the Laurentian gneiss on which they rest, and 

 are un conformably surmounted by the lowest Silurian rocks of the 

 Highlands. 



3. These lowest Silurian rocks, chiefly hard granular quartzite, 

 which rise into lofty mountains, and contain intercalated masses of 

 fossiliferous limestone, are all so thoroughly exposed in precipitous 

 or highly inclined escarpments, that if they contained any auriferous 

 veins the same must have been detected. 



4. The next overlying group, consisting of chloritic micaceous 

 flags and schists, which, as they dip away to the E.S.E., become 



^ In Gaelic, Sceirea Beinn. 



