GEOLOGY OF NOKTHERN WISCOXSIX. 47 



localities the upper conglomerates and sandstones accompanyino: 

 the Copper-Bearing series have not been seen. For asserting that 

 they are the representatives of each other — I have among others 

 the following reasons: 



1. Cupriferous strata have been traced uninterruptedly from the 

 extreme end of Keweenaw Point to Long Lake in Bayfield county 

 a distance of over 200 miles. The apparent thickness of the for- 

 mation is never less than 20,000 feet, and is often even 60,000 feet. 

 Fifteen miles west from Long Lake, Dr. Wight found the Cuprifer- 

 ous series represented at the Eau Claire Lakes. From here, in the same 

 general southwesterly direction, the distance to the out-crops on the 

 St. Croix is about 60 miles. Exposures of "trap-rocks," have been re- 

 ported by explorers at numerous localities between the two points. 

 There can be no doubt then, that the Kettle River Range is merely 

 a westward prolongation of, and is directly connected with, the 

 "mineral range " ot Keweenaw Point, upon which the most famous 

 copper mines of the world are located. From facts which have 

 been obtained mainly from explorers, and also from Dr. Owen's re- 

 port, I am satisfied that the range extends forty or fifty miles into 

 Minnesota before it is covered by later strata. 



2. The region has been very little examined, and the conglomer- 

 ates might escape observation. 



3. There is probably a gradual thinning out of the conglomer- 

 ates towards the west. At the mouth of the Montreal River, the 

 conglomerates and interstratified sandstones and shales have a thick- 

 ness of 10,000 feet, while on Bad River, but eighteen miles to the 

 west, the exposed thickness is but a few hundred feet. On the St. 

 Croix River the thickness is still less. Owing to this thinning out 

 they have been largely removed by erosion. 



Northeast from the Kettle River range there is a space of forty 

 miles along the St. Croix River, although only about four miles at 

 right angles to the trend of the formations, upon which rocks in 

 place were not observed. At Sawyer's dam, on section 16, town 

 42, range 14, west, southward dipping sandstones and shales were 

 found. For fourteen miles along the stream, in a southeast direc- 

 tion, the strike and dip are very persistent. The strike corrected 

 for variation is north sixty degrees east, and the dip fourteen de- 

 grees to the southeast. The greatest horizontal distance across the 

 formation is three miles. A trigonometrical calculation therefore 



