838 ME. J. H. C01LI]!fS ON THE SIJDBUEY C0PPEE-DEP0SIT8. 



neighbourhood of the deposits. It is true there is not much felspar 

 present, and that little is not orthoclase, hence perhaps the dif- 

 ference in this respect. At Eio Tinto kaolinization is very marked. 



h. As at Eio Tinto and in the Sierra Morena generally, so at 

 Sudbury, the actual presence of pyritous matter is indicated by the 

 existence of a highly ferruginous subsoil ; but in the latter region 

 there are no ancient lake-deposits of iron-ore like those capping the 

 Mesa de los Pinos at Eio Tinto*. This, however, is a local dif- 

 ference in respect only of a secondary deposit of comparatively 

 recent origin and of no genetic importance. 



In conclusion, I would remark that whatever may be the cause 

 of the important differences in the nature of the pyrites at Sudbury 

 and in the south of Spain, there is no reason to suppose that it 

 results from the differences in the containing rocks, since similar 

 differences are frequently observed in the pyritous deposits of 

 Canada when the country rocks are identical. It is possible that a 

 more minute examination of the various Canadian deposits would 

 throw light on this important subject ; but hitherto such an in- 

 vestigation does not seem to have been made. 



[Note, October 22, 1888. — Yery little work has been done since 

 the above was written except at the Evans Mine, where the ore is 

 said to have the following average composition : — copper 3 per cent., 

 nickel 3^, iron 40, sulphur 24:, rock 49|. It is proposed to erect 

 concentration- and smelting-works, and to ship the nickeliferous 

 " matter " to the United States for subsequent treatment!; but as yeb 

 this is a proposition only.] 



DlSCTTSSIOlf. 



The Peesideis^t observed that the comparison of these deposits 

 with those of other regions constituted a valuable feature in the 

 paper. 



Mr. Attwood confirmed the statements of the Author as to these 

 deposits occurring in the Huronian, consisting of gneiss, quartzites, 

 and clay-slates. There was an abundant occurrence of diorites, 

 which in his opinion had brought up the metals. These diorites 

 strike N.E. and S.W. He had seen no evidence of contact-deposits ; 

 the diorite-intrusions were very plainly shown intersecting the clay- 

 slates, &c., by examining the railway-cutting south of Sudbury, 

 on the Algoma branch. 



* Op. cit. pp. 253, 263. 



