J>4 Mr. T. Sterry Hunt 



limestone. These strata, with an eastward dip, are covered by other 

 quartzites and limestones, to which succeeds the great gneissoid 

 formation of the western Highlands, consisting of feldspathic, chlo- 

 ritic, micaceous, and talcose schists resembling closely the gneissoid 

 rocks of the Green Mts. and including the chromiferous ophiolites 

 of Perthshire, Banff and the Shetland Isles. 



This gneissoid series was by Prof. Nicol suggested to be the 

 older or Laurentian gneiss brought up by a dislocation on the 

 east of the Silurian limestones, but Sir Roderick Murchison, with 

 Messrs. Ramsay and Harkness, has shown not only from the dif- 

 ferences in lithological character, but from actual sections, that 

 the eastern gneissoid series is made up of altered strata newer 

 than the Sikirian limestones.* Thus in geological structure 

 and age, not less than in lithological and mineralogical characters, 

 the rocks of the western Highlands are the counterparts of the Lau- 

 rentian and Silurian gneiss formations, as seen in the Laurentides and 

 Adirondacks, and in the Green Mts. The same parallelism may 

 be extended to Scandinavia, (where Kjerulf and Forbes have 

 shown much of the crystalline gneiss to be of Silurian age,) mark- 

 ing as it would seem the outer edge of a vast Silurian basin, which 

 may be followed in the other direction across the Atlantic to the 

 Gulf of Mexico. We also remark in Great Britain as in America, 

 that whereas the northern outcrop of the palaeozoic basin offers at 

 its base only a series of quartzose sandstones reposing upon the 

 Laurentian system and characterized by fiicoids and Scolithus, we 

 find further south in England an immense development of shales, 

 sandstones and conglomerates, which form the base of the Silurian 

 system and correspond to the Primordial zone and the Quebec 

 group. 



We have said that upon Lake Huron and Superior the sand- 

 stones of the upper copper-bearing rocks are the equivalents of 

 the Quebec group. The clear exposition of the question by Mr. 

 J. D. Whitney in the Am. Mining Jour, for 1860 (p. 435) left little 

 more to be said, but the sections made last year by Mr. Alex. Murray 

 of the Canada Geological Survey place the matter beyond all doubt. 

 On Campment d'Ours, a small island near St. Joseph's, the sand- 

 stones of Sault St. Mary are seen reposing horizontally on the 

 upturned edges of the Huronian rocks, and overlaid by limestones 

 ■which contain in abundance the fossils of the Black River and 



* Murchison, Quar. Jour. Geol. Society, Vol. xv. 353 and xvi. 215. 



