1872.] NICHOLSON NORTH SHORE OF LAKE SUPERIOR. 17 



brief geological account of the mining-districts of Thunder Bay and 

 Shabeudowan, both of which are likely to become ultimately of 

 great importance. Though as yet very imperfectly explored, and 

 still more imperfectly opened up and developed, the entire north 

 shore of Lake Superior has already been shown to be intersected 

 by numerous metalliferous veins, and promises to equal in richness 

 the most celebrated mining-regions of the North American con- 

 tinent. At present, however, I shall confine my attention to the 

 silver-bearing district of Thunder Bay, and the auriferous region 

 which surrounds Lake Shabeudowan. 



Thunder Bay, Black Bay, and ]S T eepigon Bay are three remarkable 

 bays on the north shore of Lake Superior, almost shut off from the 

 main lake by islands, and assuming more or less the character of 

 independent lakes. The first of these is the most westerly, and is a 

 beautiful sheet of water, about 28 miles in length and 12 miles 

 across. On its northern shore are situated the settlements of Port 

 William and Prince Arthur's Landing, the former a Hudson's Bay 

 port of comparative antiquity, the latter a newly established town, 

 destined to be the centre of the silver-mining district. The chief 

 river flowing into Thunder Bay is the Kaministiquia, a large and 

 important stream, which drains a series of lakes lying to the north 

 of Lake Superior, and which debouches into the latter at Port 

 William. The bay, as viewed from its northern shore, appears to 

 be almost land-locked, and presents several features of striking 

 interest, both from a geological and an artistic point of view. 

 Pacing Prince Arthur's Landing, to the south-east is the bold and 

 bare prominence known as Thunder Cape, which is 1350 feet above 

 the level of the lake, and more than 2000 feet above the level of the 

 sea. The lower portion of this rugged elevation is formed of black 

 argillaceous shales, whilst the higher portion is constituted by a 

 vast tabular mass of columnar trap interstratified with the former. 

 Both of these belong to what Canadian geologists term the " Copper- 

 bearing Series," of which I shall have to speak again. The mouth 

 of Thunder Bay is divided into two channels by several islands, the 

 largest of which is Pie Island, which derives its somewhat un- 

 romantic name from the presence on its western end of a great 

 rounded, flat-topped, pie-shaped mass of trap, forming a con- 

 tinuation of the great overflow of Thunder Cape. To the west, 

 again, on the mainland, and beyond the mouth of the Kaministiquia 

 river, the same trap is continued into a great series of rugged hills, 

 of which the one known as " Mackay's Mountain " has an elevation 

 of 800 feet above the level of Lake Superior. 



The rocks which immediately surround Thunder Bay belong to 

 the so-called "Lower" and "Upper Copper-bearing Series" of 

 Canadian geologists. The relations which subsist between these 

 two groups have not yet been satisfactorily determined ; and the 

 age of both is still a matter of opinion. The Upper Copper-bearing 

 series consists essentially of red, white, and grey dolomitic sand- 

 stones, red sandstones and shales, reddish limestones, indurated red 

 and yellowish marls, red sandstones and conglomerates, and inter- 



VOL. XXII. PART L C 



