DEEP MINING IN NOVA SCOTIA — PREST. 429 



subjected prevents our knowing- anything on this point. How- 

 ever, there is enough left to show that the original surface of 

 the larger folds would on an average be nearly 25,000 feet above 

 the present surface. Denudation is shown best on the Sissibou 

 River, Mt. Uniacke, Dollard's Lake and Molega. On the Sissibou 

 where the greatest width is shown erosion has laid bare a section 

 over 25,000 feet thick.* 



Of the vast erosion of the Cambrian rocks by far the greater 

 portion is Pre-Carboniferous. The evidence for this is seen in 

 Newport, Musquodoboit, Gay's River, Carrol's Corner and other 

 places. At each of these places the Lower Carboniferous is seen 

 overlying the slates and quartzites which have already been 

 eroded to a depth, in some places, of over 20,000 feet. Near th^ 

 head of St. Mary's Bay, Digby County, the bulk of the evidence 

 seems to show that the Triassic sand-stones were not deposited 

 until the Sissibou anticline had been eroded to almost or quite 

 its present depth. 



If, as has been maintained, our granites were crystallized under 

 great pressure, then the Cambrian slates were at most only 

 slightly eroded when the early Devonian metamorphism took 

 place ; otherwise the granite would be deprived of that immense 

 weight necessary to its crystalline form. Under this supposition 

 this immense denudation would all be included in the Devonian 

 age. Even if this supposition was swept aside, the incontro- 

 vertible fact still remains that only to the interval between the 

 Cambrian and the Carboniferous can we refer nearly the whole 

 of this stupendous operation. 



The bearing of this fact on the question of deep mining is 

 this — viz : that even in Pre-Carboniferous times denudation had 

 already exposed the lowest observable strata of our gold fields 

 and had carried on deep mining to a depth of over 20,000 feet, 

 laying bare the pay streaks which have often been asserted to be 

 only surface deposit 



*A summary of my notes on the Sissibou section is as follows : — 



From anticlinal apex in blue quartzite up to purple slates Sf miles. From purple slates fo 

 fossiliferou'i slates or beds immediately underlyin<r them '2§ miles. Total 6 miles. Average dip 

 321° 30' at an an.^le of 65°. Resulting thickness (at right angles to bedding) 28,723 feet. 



However, to cover all possible errors of measurement, unseen faults, &c., I strike off over 

 3,000 feet. 



