70 REPORT OF THE 



Still higher, is a massive limestone, below, filled with Bryozoa, 

 Enorinites andBrachiopods, above, little fossiliferous, the whole, 

 with interlaminations of clay. 



At the upper rapids of Thunder Bay river, still a different but 

 entirely detached section was observed, and it is, as yet, impos- 

 sible to collocate it with the others. The same must be said of 

 the isolated exposure at the lower rapids. At the upper rapids 

 (N. E. | of S. W. \, sec. 1, T. 31 N., 8 E.,) on the south side of 

 the river, limestone is seen in a bluff 15 feet high, dipping E. 



5. E., about 5°. The whole section exposed is 25 feet, made 

 up as follows, from above:* 



8. Limestone, bluish, flaggy, 8 ft. 



1. Limestone, dark gray, highly crystalline, thick bedded, 



with Favosites, 9 ft. 



6. Limestone, dark bluish, very fine grained, hard, com- 



pact and heavy, with a few reddish streaks and spots, 

 and some encrinital stems and shells, and a few crys- 

 tals of spar interspersed, with occasional seams of 

 the same in the form of dog tooth spar. Would make 

 an excellent building stone, and probably would re- 

 ceive a fine polish, 6 ft. 



5. Limestone, gray, crystalline, thick bedded, seen in bot- 

 tom of river. This rock resembles fragments seen at 

 the highest level about the lower rapids, 2 ft. 



'4. An interval of no exposure. Half-amile higher up the 

 stream, the section is continued, as follows: 



3. Limestone, dark, bluish- gray, fine grained, compact, in 

 layers 2-4 inches thick. Resembles the rock at the 

 lower rapids. 



2. Clay, indurated, regularly stratified, rather dark, 3 J fL 



1. Calcareous shale, with fossils, forming the bed of the 

 river. 



The dip at this place is abnormal and evidently local. The 

 true geological position of the rocks must be determined by 

 future investigation. 



The rocks of the Hamilton Group are traced from the south 

 shore of Little Traverse Bay to near the outlet of Grand Tra- 

 verse Bay. At some of the exposures Spirifer mucronatus is 

 recognized in great abundance, though by far the most abund- 

 ant Brachiopod is Atrypa reticularis. % 



♦In all the sections given in this Report, the numbering proceeds from below. 



