ANNUAL REPORT FOR 1874. 47 



range of ore beds extending eastward from Black Eiver Falls; a very 

 important question that might be determined, by the explorations 

 thus to be made. 



Before commencing the field-work of the season, Prof. Irving pre- 

 pared the supplementary report herewith submitted, embracing de- 

 tails of results attained in 1873, which, for want of time could not, as 

 before stated, be included in his general report for that year, now de- 

 posited in the office of the secretary of state. This supplementary 

 report, covering seventy-four pages of manuscript, with several maps, 

 diagrams and sections, will be found to contain much additional mat- 

 ter relating to the geology of Douglas, Bayfield and Ashland counties. 



The rocks in this part of the state are referred to five different per- 

 iods, as follows: 



1st. Laurentian — Granite, etc. 



2d. Huronian — Iron-bearing series. 



3d. Copper-bearing rocks. 



4th. Potsdam sandstone. 



6th. Quaternary — Drift, etc. 



Many facts and arguments are adduced to show that this is the 

 proper order of arrangement, and ample details are given, so that geo- 

 logists may judge of the correctness of these views. 



Prof. Irving has been able to show the existence of a synclinal axis 

 extending in a soifthwesterly direction, through these counties, being 

 the westward inland extension of the great trough between Keweenaw 

 Point and Isle Eoyale, occupied mostly by the waters of Lake Su])er- 

 ior. We thus have a more clear understanding of the different direc- 

 tions assumed by the dip of the rocks at different localities, and are 

 brought to a knowledge of one of those grand movements in the. re- 

 mote past, by which the solid rocks have been folded, contorted, and 

 lifted to their present complicated positions. To understand these 

 ancient disturbances of the strata is not only a matter of interest in 

 speculative geology, but is also one of the greatest practical import- 

 ance to the miner and to all having occasion to deal with these rocks. 



It will be seen that the Copper-bearing rocks are Pre-Silurian, 

 though not as old as the Huronian. Prof. Irving's conclusions on 

 this point are that: 



Ist. " The beds of the Copper-bearing series and those of the Huro- 

 nian were once spread horizontally over one another, including the 

 whole series of tilted sandstone on the Montreal river; they were dis- 

 turbed by the same force, and received their present tilted positions at 

 the same time, as evinced by the entire conformability of the two series. • 



