156 LOWER PENINSULA. 



progress upward, began to rise from the lower beds to the higher, 

 and this several times repeated. 



At the mouth of Iron River, brownish, thin-bedded, sand-rock 

 layers with intermediate shaly seams are seen in the banks, with 

 an approximate strike northwest and a northwest dip. A short 

 distance up the river runs in rapids over rocky bars, obliquely 

 crossing its bed, which are lower strata than those at the entrance ; 

 their strike is about 15° north of west, with a dip east of north 

 at an angle of about 20°. Ascending in the river channel, we 

 pass over the edges of constantly lower and lower strata ; these 

 lower beds are dark bluish or blackish gray slaty layers of a 

 fine-grained, sandy and argillaceous rock with fine micaceous 

 scales ; the surfaces of the thin slabs are ripple-marked. With 

 the ascent the dip and strike of the strata constantly change. At 

 a no greater distance than 150 steps above the former place 

 where strike and dip were measured, the strike had changed to be 

 south of west with a dip south of east. The strata here are still 

 lower, thinly laminated flagstones containing some calcareous ce- 

 ment, but of the same dark, arenaceous, slate-like rock mass as the 

 higher beds. The dark rock contains globules of calcareous concre- 

 tions, and seams of softer shaly structure alternate with the ripple- 

 marked harder slabs. Weathering slaty pieces are covered with a 

 green efflorescence of carbonate of copper oxide. We have arrived 

 now at the foot of low, stair-like falls, where, by a bend of the 

 river, across the strike and with the dip of the strata, which latter 

 is here south of east, instead of descending further in the series as 

 we were doing, we ascend, step by step, into higher beds, simi- 

 lar in character to those seen before. 



By another flexion of the river bed, it comes parallel with the 

 strike of the strata, and without ascending or descending in the 

 series, we move up its course, remaining on the same horizon ; but 

 soon, by another bend, a descent into lower beds, while still ascend- 

 ing the river, begins. The stamp works of the Ontonagon Mining 

 Company are now in sight ; the strike of the strata approaches 

 gradually an almost due east and west direction, with a dip north- 

 ward at a steep angle, and still, while ascending the river, we stead- 

 ily descend upon lower beds. The rock below the stamp mill is in 

 thicker, much more massive beds than seen before. Some seams 



