1869.] JOASS SUTHERLAND GOLD-FIELD. 325 



6. The material in which the granular gold occurs, namely the 

 detritus overlying the abraded edges of the flaggy Lower Silurian 

 rocks, may be partly of glacial origin, but is not necessarily far- 

 travelled, for its included boulders seem to be of local origin. It 

 has been arranged by water, but probably that of the streams near 

 which it lies and not that of the sea, judging from the unwashed 

 moraines which occur at lower levels in the valley of the Brora. 



The extent of the auriferous country will probably be found to 

 correspond with the range of the more highly metamorphosed Lower 

 Silurian rocks ; and since these may be found in. more or less force 

 as far as the northern coast of Sutherland, the area of the gold-field 

 may yet, perhaps, be extended. IN'early every stream within the 

 area here described has been well searched by practical diggers ; and 

 the fact that many of them, as already mentioned, have been searched 

 in vain, suggests no wide-spread deposit, the result of extensive gla- 

 ciation, but several independent centres connected with the local rocks. 



The question of the continuance of gold-seeking as a source of 

 remunerative labour must depend upon the extent to which these 

 its parent rocks may be found to occur. This can only be ascer- 

 tained by systematic prospecting, which will doubtless be encouraged 

 when questions now pending between the agents of the Crown and 

 those of the noble proprietor of the ground are satisfactorily settled. 



Already the results have been a fair return for skilled labour, 

 amounting to the value of about .£3000, so far as I can ascertain by 

 inquiry and careful calculation. 



In conclusion, it may perhaps not be held irrelevant to remark 

 that the Pictish Towers, a class of ancient buildings very numerous 

 in Sutherland, are specially abundant within the ascertained auri- 

 ferous district, and further appear, wherever they occur, from Shet - 

 land to the south of Inverness -shire, to be associated with rocks which 

 may be more or less auriferous — namely the Lower Silurian, believed 

 on very high authority to be the most frequent source of gold in all 

 parts of the world. 



These forts were apparently erected against maritime invaders. 

 Their number and strength suggest the frequency and formidable 

 nature of such invasions, for which a motive may be found in the 

 supposition that south-eastern Sutherland and other districts where 

 such duns or burgs occur were known in prehistoric times to be 

 rich in gold or other mineral treasures. Hence, perhaps, the con- 

 nexion between the copper of Sandness and Mousa-burg in Shet- 

 land, the lead and silver of Beaufort and Struidh-burg in Inverness, 

 the gold of Durness and Dun-Dornadilla in "West Sutherland, of 

 Uisge-dubh and Caisteal-CoiUe, of AUt-Smeorail with Aschoille- 

 burg on one side, and Coir-Aoiscaig tower on the other, and of 

 Strath TJUie, with its chain of Pictish strongholds from Dun-uaine 

 on the coast to the wonderful group of Cyclopean structures that 

 crown Beinn-Ghriam-beg twenty- eight miles inland. 



Hence, too, perhaps, the origin of the native torques and ar- 

 millse of beaten gold, attractive booty no doubt to the roving Norse- 

 men, '' the exactors of rings ; " and hence, also, it may be, one 



