146 



FORMATIONS OP 



THE 



INTERIOR 



I remark, however, that the granite, in the vicinity of Vermilion Rapids, of the 

 Chippewa, bears a close resemblance to the granite of Limoges and Chautelonpe, 

 in the Department of the Hante Vienne, in France ; in which latter are found 

 emeralds, phosphate of lime, phosphate of iron, phosphate of manganese, phosphate 

 of uranium, variegated copper, arsenical iron, oxide of tin, kaolin, and garnets. 



Though none of these minerals were discovered on the surface, within the range of 

 our observations, it is possible, that mining operations, carried to some depth in 

 that formation, might disclose one or other of them. Unless, however, future 

 superficial examinations disclose more encouraging indications than anything we 

 have yet met with, the chance of productive return is, in my judgment, too small 

 to justify such an enterprise. Mining operations would here be conducted under 

 great disadvantages. The rocks usually lie so near the level of the general drainage 

 of the country, that shafts and adits would be most likely speedily inundated ; and, 

 at any considerable distance from the rivers, the expense of sinking through a thick 

 mass of loose, incoherent, superincumbent material, would be a source of great 

 expense. 



As heretofore alluded to, near the junction of the green and red chloritic schistose 

 rocks, on Township 21 north, and Range 4 west, these rocks assume a highly ferru- 

 ginous character, and pass gradually into heavy beds of oxide of iron ; and magnetic 

 disturbances, observed during the land surveys in that neighbourhood, prove 

 these iron beds to be of considerable extent. Mr. J. P. Cathcart's survey of the 

 townships on Black River showed, on the line between Townships 21 and 22, of 

 Range 3 west, of the 4th Principal Meridian, running west, a variation first 

 of 8°; at the end of the first forty chains, a variation of 2° 15'; at the end of 

 the next forty chains, of 2° 30' ; at the end of the first mile, of 5° ; at the end of 

 the next mile of 13° 35' ; the average variation being 8°. 



Near the Falls of the Chippewa, in a similar geological position, I observed 

 similar indications of iron. 



On the head-waters of Prairie a la Crosse, Mr. Dunn, United States Surveyor, 

 noticed extraordinary variations of the needle, ranging from 5° 20' to 17° 30'. 

 There is good reason to believe that, at these and probably at other localities along 

 the range of the same formation, bodies of iron ore exist, in productive quantities. 



Some earthy carbonate of copper has been found in place, to a limited extent, in 

 connexion with the Trap Ranges of the St. Croix, but not in sufficient quantities or 

 richness* to induce those holding claims to undertake mining operations. 



In addition to the considerations derived from the average yield of the copper 

 earth, and the poorness of the superficial veins, it may be useful to remark, that the 

 Trap Formation of the St. Croix, though probably a spur from the Porcupine 



* A sample of copper ore, said to Lave been obtained from a crevice in the trap near the Mill on the 

 St. Croix, was taken to Boston, and analyzed by Mr. Hayes, who found it to contain, according to the 

 statement of Mr. Brownell, 19-77 pure copper. 



Average samples, obtained near the same place, were subjected to analysis in my laboratory, with a very- 

 different result, the ore itself only yielding, on an average, four to five per cent., and the poorer copper 

 earth but one to two per cent. I am induced to believe that the discrepancy in the two analyses arises 

 from the fact that Mr. Hayes was handed for examination a choice, picked specimen. 



