1869.] JOASS — SUTHERLAND GOLD-FIELD. 317 



more and more gneissic in character, and, perforated as they are 

 at intervals by granitic and porphyritic rocks, have, in all proba- 

 bility, afforded the auriferous delritus of Eastern Sutherland. These 

 rocks, which formerly were not separated from the old or funda- 

 mental gneiss, though they have the true Silurian strike from S.W. 

 to N.E. (which is rectangular to the strike of the Laurentian rocks), 

 are in parts intensely metamorphosed, whether it be in the high 

 plateau south and west of Tounge, or where they roU over until 

 they reach the eastern slopes of Sutherland and Ross, having in 

 both localities been powerfully affected by eruptive rocks. Judging, 

 then, from the composition of these various rocks, and particularly 

 those described by Mr. Joass, we need not travel further westward 

 from these eastern slopes than to the great central plateau to look 

 for the origin of the gold- detritus ; and when we examine the ma- 

 trices of the auriferous fragments we find that this inference is sus- 

 tained by their composition. 



rinally, I am led to infer, from my acquaintance with the rock- 

 formations of the N^orth Highlands, that there is little chance of 

 discovering in them any notable bodies of rock in situ charged with 

 rich auriferous bands analogous to those which are associated with 

 the Lower-Silurian slates and schists of Australia and California. 



Notes on the Sutherland Gtold-pleld. By the Rev. J. M. Joass. 



It is proposed to arrange the following remarks as under : — 



1. The extent of the gold-field as at present ascertained. 



2. The general character of the prevailing rocks. 



3. The associated rocks. 



4. Detailed descriptions referring to map and sections. 



5. Probable source of the gold. 



6. General remarks, 



1. The extent of country over which gold has been ascertained to 

 occur in the south-east of Sutherland and contiguous portion of 

 Caithness may be stated as measuring 30 miles from east to west, 

 and about 20 from north to south. This is exclusive of several 

 widely detached places in the north-west and south-west of the 

 county, where small quantities of gold are credibly reported to have 

 been found. A few points in the north of Caithness, and IJnst, in 

 Shetland, are held to be auriferous. 



2. The prevailing rocks of the district are believed, on the autho- 

 rity of Sir R. I. Murchison, to belong to the Lower- Silurian series. 

 This may be regarded as settled by his masterly analysis of the 

 evidence for the intimate connexion of these rocks with large de- 

 posits on the north-west, which from their included fossils are ad- 

 mitted to belong to that system. Within the district referred to, 

 these rocks occur as flaggy micaceous, gneissose, and quartzose 

 strata, with a south-easterly dip. With a few local exceptions this 

 dip is unaffected by the presence of numerous igneous rocks, whose 



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