OF CENTRAL CANADA PART III. 195 



examples are rare in Canada. (4) Spheroidal Veins. In these the 

 ore lies in the gangue in the form of spheroidal masses composed of 

 concentric layers. Well-defined examples of Canadian occurrence do 

 not appear to have been recorded, (5) Brecciated Veins. These form 

 the great majority of mineral veins hitherto observed in Canada. 

 The gangue contains angular and other fragments of well-rock, with 

 the metalliferous portions of the vein arranged between and around 

 these, occasionally in more or less distinct layers. The rock-frag 

 ments are often traversed by thin strings of ore. When of large 

 size, they form the so-called " horses " of the miners. These horses 

 sometimes cause a good deal of trouble by coming in a direct line 

 with the shaft, as happened at the Shuniah vein on Thunder Bay, 

 Lake Superior, and in one of the shafts at the Ives Mine in the 

 Eastern Township of Bolton. 



Great obscurity prevails with regard to the processes by which 

 vein-fissures have been filled with their contents ; but, in the majority 

 of cases, several distinct agencies, acting both simultaneously and 

 consecutively, have evidently been concerned in the repletion of these 

 fissures. Some observers have sought to maintain that all the 

 various matters found in veins were originally diffused through the 

 mass of the surrounding rocks, and were drawn into the fissures by 

 electrical currents passing through these : although they fail to 

 explain how currents of this kind could possibly effect the operation 

 in question. Others assume the mineral matters, in veins, to have 

 been extracted from the surrounding rocks by the solvent power of 

 water, and thus to have been gradually carried into the fissure. 

 Many of the sparry, and some of the metallic matters, occurring in 

 veins, may have been derived in this manner from the surrounding 

 rocks ; but the supposed presence of diffused metallic matters in 

 these rocks, considered generally, is, it must be remembered, entirely 

 hypothetical, and open to many objections. On the other hand, we 

 have undeniable proofs in volcanic and other districts, that metallic 

 matters, in many respects similar to those found in veins, or capable 

 of being converted into such by known chemical changes and decom- 

 positions, are actually brought from deeply-seated sources, both as 

 sublimed products, and in solution in thermal springs. The weight 

 of evidence, therefore, leads to the inference th&t the contents of 

 veins generally, are due to endogenous action, rather than to surface 



