(JEOLOGICAL EXPLOKA.TIONS AND LITEH ATIIRE. 25 



I will now proceed to explain the geolog-ical rehitious ot' this vast bed of magDetic 

 irou ore, show bow it is associated with other locks, and its mode of occurreuce aud 

 eharacteristios. 



The geueial direetioii of the range is about 12° north of east, and south of west' 

 and this is also the tlireetion of the strike of the seveial strata of which it is composed. 

 The dip, or inclination of the layers of rock, is toward the north and at light angles to 

 the strike. The dip vaiics from ;J0° to 60°, and in a few cases it is almost perpendic- 

 ular, or 90°. West of. Bad river the dip is usually less tiian it is east of that stream. 



The rocks with whu'h the ore is immediately associated are of the kind called 

 Primary or Azoic, having been formed, as is supposed, at a very early epoch, and 

 prior to the existence of animal life upon the earth. 



The lowest formation noticed at the base of the range on the south side was a 

 light colored, often white, quartz rock, consisting of minnte. closely aggregated grains 

 of tjuartz or saud. Sometimes this rock forms a large jiroportion of the height of the 

 cliff; at other places it is (|uite subordinate. 



Next above the quartz rock, aud often alternating with it, is fouud a chloritic 

 slate, . . . more or less silicious; in some localities so much as to resemble the 

 novaculite or oil stone, aud might be used for whetstones, though we saw none ot 

 much fineness of texture. In many respects this slate is one of much interest, being 

 often associated with metallic ores, and at this place actually passing into irou ore- 

 As we ascend toward the north, the slate gradually becomes more and more ferrugi- 

 nous, until it is changed to a very pure iron ore. , . . It is often quite ditficult 

 to decide by the external characters alone where the slate rock ends and the slaty 

 iron ore begins, so gradual is the change. The ore possesses the same slaty character 

 and has the same dip or inclination of its layei-s. 



Immediately above the ore (or north of it) is found a very hard rock, . . . 

 with obscure marks, indicating its (u-igiual'slaty structure, which is supposed to be 

 hardened (metamorphic) slate. It is everywhere filled with thin seams of highly 

 magnetic ore. These seams . . . vary in thickness from one eighth of an inch to 

 several inches, and correspond in directiou and dip with the mass of the rock. Thej' 

 are so hardened and so intimately connected with the rock in which they are 

 imbedded that the ore can not l)e separated ; and it is, therefore, only when these 

 seams are so abundant as to justify the smelting of the whole (ore and rock) together 

 that they possess practical value. It forms the crest aud north slope of the range, 

 except where covered with drift. . . . 



These several rocks — the quartz rock, chloritic slate, magnetic iron ore (for this 

 is so extensive here that it may be ranked as a rock formation), the '-hard rock," and 

 the d*ift — are all coextensive with the range, so that wherever we find either we 

 could with certainty predict the occurreuce of the others in the proper relative 

 order. . . . 



