APPENDIX A. 



OBSERVATIONS MADE ON A CURSORY TOUR THROUGH 

 THE ONTONAGON SILVER MINING DISTRICT. 



The discovery of silver in the sedimentary rock beds of Iron 

 River, in Ontonagon County, has recently attracted considerable 

 attention on the part of miners and capitalists. 



On my return from the examination of the Huron slate quarries, 

 of which the report is given elsewhere, some gentlemen of Mar- 

 quette, interested in the new mining district, asked me to go along 

 with them and examine into the conditions under which the silver is 

 found, which invitation I gladly accepted. In the first report on 

 the Upper Peninsula, little has been said about the region in 

 question, and at the time of its issue the discovery of silver had 

 not yet been made, for which reason I think that the small contri- 

 bution which I can add to our knowledge of this mining country 

 will be welcome to those interested in its geology and in the de- 

 velopment] of its mineral resources. Ontonagon district has the 

 same geological structure as the northeasterly part of Kewenaw 

 peninsula, of which it is a direct continuation. 



A ridge of copper trap, with a strike from northeast to south- 

 west, and with a northern dip, divides it into an east and west 

 part. The east part is a mountainous plateau with marshy flats,, 

 from which Ontonagon River collects its waters through branches, 

 one of which is fed by a large inland lake, the Gogebic Lake. 



After winding its way for a while along the foot of the ridge, and 

 having united with its affluents from the south and north, the 

 Ontonagon breaks transversely through the trap range and hastens 

 in a direct northwestern course down the western slope to the 

 lake. 



The surface rock of this east side of the central trap range is 

 the red Lake Superior sandstone inconformably abutting against or 

 overlapping the trap rock, with horizontally disposed layers. 



