70 REPORT 1870. 



Specimens of the rocks traversed are preserved. On the French side the work 

 began by 420 feet of tunnelling through disintegrated and decomposed rock, repre- 

 senting an actual thickness of about 200 feet of weathered material. After this 

 there was 6000 feet of tunnelling (3600 feet of rock) through talcose and steatitic 

 schists, with carbonate of lime and magnesia, containing hyaline quartz and crystals 

 of calcite and dolomite. Among the rocks was a conglomerate, and at the bottom 

 coarse micaceous gi-itstone. Beyond these was 800 feet (actual thickness) of very 

 hard quartzite, and then 1800 feet of gypsum, crystalline limestone, and talcose 

 schist. All these belong to the upper and middle divisions of the anthracitiferous 

 rocks of the Alps, ranging from the Oxford clay to the lower oolites, both inclusive. 

 All the rest of the tunnel is through a vast series of schistose limestone and cal- 

 careous schists, often steatitic, at least 18,000 feet in actual thickness, representing 

 the Lias, the Rhjetic rocks, and perhaps some Triassic rocks. Throughout these 

 are many instances of slickensides, and a few crystals of iron-pyrites and galena. 



The author pointed out that the effect of pressure on these rocks was inappre- 

 ciable, except that they exhibited numerous small folds. There are very few 

 crevices and fissures ; these were almost all partly filled with crystals. 



Observations on temperature were made, but not very systematically, at dis- 

 tances of about 500 metres, by bore-holes put in laterally to a distance of about 

 three metres. At 6200 metres (20,.342 feet), at a depth of more than 5000 feet, 

 the thermometer showed 27° 0. This would show a rate of increment of one 

 degree Fahrenheit in upwards of 100 feet. This is confirmed by other observations 

 on the temperatm-e of the rock, and also of the water met with in the various 

 fissures. 



The quantity of water yielded during the tunnelling has been exceptionally small. 

 Except on two or three occasions, where ^small water-containing fissures were 

 tapped and water came off under pressure for a few hours, the general quantity has 

 hardly varied, and does not exceed 4 litres per second (say, 100,000 gallons per 

 day). The water contained oxide of iron and sulphates of lime and magnesia. 



On the Matnx of tJie Gold in the Scottish Oold-JleJds. 

 By James Bktce, M.A., LL.D., F.G.S. 



Up to July of last year, the source of the gold of the alluvial workings in 

 Sutherland had not been determined. Many of the miners had been at other 

 diggings, where the gold occurred in quartz reefs, and accordingly their search was 

 constantly directed to the discovery of such reefs, but without success. Sir R. I. 

 Murchison, Rev. J. M. Joass, Mr. John F. Campbell, and Mr. Cameron, in their 

 several papers, had all ofiered surmises on this point ; but no definite infonnation 

 had been made public. The author had directed his attention to the elucidation 

 of this point; he had not succeeded in detecting any quartz reef, but he had 

 foimd the gold in its native seat in another rock. The banks of the Suisgill burn 

 consisted of alternating coarse whitish granite and a highly crystalline mica-slate. 

 On crushing the granite and washing the sand, grains of gold were found in every 

 specimen. A similar result was obtained by crushing and washing specimens of 

 the mica-slate, but the gold was less abundant, and was absent from several spe- 

 cimens. 



A structure very similar existed in the Kildonan bum, whose alluvia also yielded 

 gold ; but the granite here was not tested by him. He would not be understood 

 to affirm that gi'anite was the only seat of the gold ; on the contrary, he thought it 

 highly probable that it was diflused through all the metamorphic rocks of the 

 district, as Sir R. I. Murchison had supposed. He did not think it necessary to call 

 in the aid of old ice-action, as Mr. J. F. Campbell had done ; the existing drainage 

 might be credited with the whole of the gold. The specimens of granite were 

 selected by himself, and washed for him by one of the men engaged in the diggings. 



Early in the last winter gold-grains were found in considerable quantity in the 

 alluvia of the Emck and Nairn rivers towards their mouths, and were soon after 

 detected at various points far up the channels of these streams. The author had 

 examined the upper valleys of the Errick and Nairn, and found them to consist 

 of a great body of granite invading metamorphic slates. He was accompanied 



