68 THE CANADIAN NATURALIST. [Vol. viiL 



From all the foregoing we conclude that the Nipigon or Copper- 

 Bearing Series belongs to a period newer than the Huronian, and 

 although the first to follow, it is not a continuation thereof. The 

 evidences point to its being older than the Potsdam, and conse- 

 quently the deposits appear to |have been made in the Lower 

 Cambrian Age of Europe, and probably the Nipigon Formation is 

 nearly, in point of time, the American representative of the 

 Longmynd of Wales. 



e. — Occurrence of Copper. — Unlike other copper-bearing re- 

 gions, this formation holds its deposits in the metallic state. Al- 

 though the metal seems to be scattered through the whole forma- 

 tion in minute quantities, yet for mining purposes it occurs only 

 in certain beds and veins where a long process of concentration 

 has been going on, and perhaps is still in progress . The beds 

 in which copper is deposited in workable quantities are those of 

 amygdaloid and conglomerates through which the metal is distri- 

 buted in minute grains and small masses. Paying quantities are 

 usually confined to the upper five or ten feet of the beds, and the 

 proportion of the metal is more or less constant, although it ap- 

 parently traverses them in zones. 



The greater porosity of the upper portions of the trappean 

 rocks afforded more favorable conditions for the decomposition of 

 the pyroxene or hornblende, and the subsequent formation of the 

 ferruginous chlorites, and admission of other substances, as well 

 as the copper concentrated by means of aqueous infiltrations and 

 subsequent deposition by chemical or electro-chemic;il processes. 

 As a proof of electrical action, I refer to some recent experiments 

 for the Telegraph Company, by which it was found that there 

 were frequent electrical currents traversing the Mineral Hinge, 

 which often altered their courses, to the annoyance of the opera- 

 tors, until the source of trouble was discovered. 



To the south of Lake Superior numerous veins traverse the 

 Copper-Bearing Series. Those Marvine divides into three 

 groups ; the two principal systems being more or less transverse 

 to the beds : " the one trends from N. 15° W. to N. 25° W., with 

 nearly vertical dips, but to the westward ; the other, N. 16° B. 

 dipping nearly vertical, but to the eastward ; and the third trend- 

 ing with the formation, but with a steeper dip." The first sys- 

 tem is faulted considerably, while the two other systems are 

 scarcely known to be. The veins are filled with infiltrated matter 

 principally, although masses and fragments of the adjacent beds 



