380 On Metallic Minerals. 



think that a sufficient number of facts, both geological and 

 mineralogical, have been adduced, to render it highly 

 probable that the limestone of this district is of the transi- 

 tion class, while the crystalline rock below it is of the 

 primary order ; one of the youngest, perhaps, (as Doctor 

 Bigsby has said of the sienite of Marmora) of the older 

 class of rocks. Whether the latter is to be called granite 

 or sienite, appears to be a mere dispute about words, in 

 which I shall take no part, conceiving that whatever the 

 minerals may be which are present, either predominating 

 or otherwise, that the different aggregates are of contem- 

 poraneous formation, and pass one into the other. 



A question has been mooted out in this country, whether 

 a genuine granite, that is an aggregate composed exclu- 

 sively of quartz, felspar, and mica, of a very crystalline 

 texture, and exhibiting no signs of a mechanical formation 

 has been observed; as far as my experience extends, such an 

 aggregate is very rare, nor can I say positivelT/, that I ever 

 saw such, under any other form than as veins traversing 

 other rocks. Hand specimens may be frequently seen and 

 collected, in which the necessary conditions appear to be 

 present ; but no individual, ambitious of being thought a 

 geologist, will judge from such partial data. Let him cast 

 them from him, and visit the rocks in situ, before he 

 presumes to give his opinion ; it will then be entitled to 

 attention though it prove erroneous.* 



• Captain Bayfield has, since the above %va< written, informed nic that 

 beds of fienuine granite arc occasionally met with on the northern coasts of 

 Lakes Superior and Huron, although, in general, the granite of those 

 districts is sicnitic, 



