No. 2.] MACFARLANE — CANADIAN STRATIGRAPHY. 99 



^' the cooling of tlie rock, and they are most likely the same as 

 '' those which occasioned a similar structure among the porphy- 

 ^' ries. The fluid rock of the diorite vein was probably in motion 

 ^' in the centre, while the parts adjoining the side walls were 

 " solidified. The current in the centre would have a distending 

 " and arranging actioti at the junction of the fluid with the soli- 

 " dified parts, and an elongation and parallel grouping of the 

 " minerals there being formed would be the consequence. Not 

 " only has this slaty texture been observed in connection with 

 " veins, but it has also been remarked that the more irre«;ular 

 '' masses of diorite assume a slaty structure towards their junc- 

 " tion with the older rocks, the stratification being as in the case 

 *' of the veins parallel with the line of such junction." 



I have thus brought into prominence three of Mr. Selwyn's 

 conclusions with which I feel bound to agree, but I have yet to 

 notice those of whose correctness I have very grave doubts. 



1. In discussing the distribution of copper ores in the Quebec 

 group, Mr. Selwyn asserts that the copper ores of his third divi- 

 sion occur both in beds and lenticular layers parallel with the 

 stratification, " but in no case accompanied by intrusive crys- 

 ^' talline rocks." This position cannot be maintained with regard 

 to the mines of Capelton. Tn the Capel mine intrusive dykes are 

 met with, and in the Hartford there is one about twenty feet 

 thick, almost vertical, with separation joints exactly resembling, 

 on its sides, the mortar seams in a stone wall. This dyke 

 appeared to influence the copper deposit quite favorably. It 

 was of a basaltic nature, but intrusions of diabase are also to be 

 found at this mine both underground and on the surface, Mr. 

 Selwyn's reference to the Acton mine is equally unfortunate. 

 The " diorite " there occurring is not itself cupriferous, and as 

 for the limestone which carries the ore, although I had opportu- 

 nities for observing it daily, it never occurred to me to regard 

 the whole mass as " vein-like," nor did it seem to behave other- 

 wise than as a bed " belono-ing to the stratification." 



2. Mr. Selwyn is unwilling to assign " either an age or an 

 ^' origin to the cupriferous diorites, dolerites and amygdaloids of 

 " the Eastern townships different from that of the almost iden- 

 ^' tical rocks of Like Superior." Leaving age and origin aside, 

 I shall mention a i'ew particulars in which the two groups are 

 {scarcely " identical." In Quebec the eruptive rocks are mostly 

 fine grained, frequently schistose, never sufficiently cupriferous to 



