94 



BULLETIN OF THE 



copper probably came up, having apparently been derived from copper- 

 ores in some inferior Azoic rocks through which the. liquid trap passed 

 on its way upward. The extent to which the rock and its cavities are 

 penetrated and filled with copper shows that the metal must have been 

 introduced by some process before the rock had cooled."* 



In the Geology of Canada, 18G3, the copper-bearing rocks are con- 

 sidered, by Sir -W. K Logan, to be of the Calciferous and Potsdam 

 formations, but overlaid by the Eastern sandstone, which was regarded 

 as Chazy (pp. G7-86). Dr. Hunt seems to regard the "ash-bed" of 

 Copper Falls as a conglomerate, and further says, regarding the Port- 

 age Lake deposits : *' Certain of the sedimentary beds thus impregnated 

 with native copper, are often designated as volcanic tufa or volcanic 

 ash. From whatever source derived, however, the amygdaloidal rocks 

 were deposited from water ; and the copper which is disseminated in 

 them, as well as in the sandstones and conglomerates, was separated by 

 chemical processes from aqueous solutions, either contemporaneously 

 or by subsequent infiltration. There appears to be no doubt that the 

 traps which are interstratificd with the sandstones and amygdaloids of 

 this region, are eruptive rocks; and the sedimentary material of which 

 the amygdaloids and tuf^is are composed may pcrhap.s have been, to a 

 greater "^ or less extent, erupted in the form of volcanic mud, as many 

 geologists suppose. This origin of the sediment has probably, however, 

 no connection with the source of the copper.'* (pp. 698, G99.) He 

 takes the entire formation, as before, to belong to the Quebec group. 



In 18GG, Mr. Thomas Macfarlane regarded the rocks at Portage Lake 

 as melaphyrs.t In 18G8 (/. c, p. 25G), he appears to regard the sand- 

 stone as being of the Permian ago, basing his conclusions upon the litho- 

 logical characters of the melaphyrs, while those who had regarded it a> 

 Trlassic have based their views upon the lithological characters of the 

 sandstone. One method is about as valuable as the other, a flow of 

 basalt lava or a deposit of saiul not being apt to be dated j^er se. Colonel 

 Whittlesey, in describing the continuation of this formation in Wiscon- 

 sin, makes the copper-bearing trap a formation below, but conformable 

 with the Potsdam sandstone, t Mr. H. Baucrman§ suggests, besides the 

 hypothesis of Muller, the folhnving to account for the occurrence of the 



* Kdition of 1862, ^i. 195 ; see also edition of 1874, p. 186. 



t Geology of Caiuulu, 1866, pp. 149-164. Canadian Nat. and Gool., (2,) HI. 



1-18. 



: Proc. Am. Assoc. Adv. Sci., 1867, XVI. 97-107. 



§ Quart. Jour. GeoL Soc, 1866, XIL 448-463. 



