146 FORMATIONS OF 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 Chauteloupe, 
in the Department of the Haute 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 
ereat 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 15° 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 4 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 have 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 percent., 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. 
