MICHIGAN AND WISCONSIN. 



485 



carefully followed up by the Hungarian River from Torch Lake, and 

 the same condition of things observed. (Ante^ pp. 113-116.) 



These observations arc of a kind to exclude any probability of a mis- 

 take ; they arc clear, and definite. Moreover, they explain the errors 

 of previous observers, and until refuted, if they can be, they conclu- 

 sively show that the Eastern san48tone and the copper bearing series are 

 one and the same geological formation, although differing in time se- 

 quence. It is a remarkable circumstance, that, while this evidence is so 

 clear and explicit, the more recent writers have carefully avoided any 

 mention of it, but have endeavored to discuss the subject on theoretical 

 grounds chiefly. 



It now becomes necessary to follow in greater detail some of the writ- 

 ings of others previous to 1879 and later, owing to the importance 

 claimed for them in the more recent discussions. The first to demand 

 our attention is a paper by Prof. R. D. Irving on the relations of the 

 Iluronian, Kowecnawan, and Potsdam Series. He states (Trans. Wise. 

 Acad. Sci., 1873-74, IL, pp. 117-119) : 



" The concluHions, then, that I would draw are these : — 

 "1. The Copper Bearing and Iluronian Series were once spread out horizon- 

 tally one over the other, and owe their present highly tilted position to one 

 and the same disturbance. 



"2. That subsequently — after a long period of erosion — the horizontal 

 Silurian sandstones were laid down over, and against tlie upturned edges of 

 the Copper Bearing Series, filling also the synclinal, in Ashland county, which 

 lies between the northward and southward dipping sandstones. 



" 3. That hence the Copper Bearing Series is more nearly allied to the Ar- 

 chaean, than to the Silurian rocks. 



" One fact observed, however, seems at first diflicult of explanation on this 

 hypothesis. In Douglas county, as already said, the horizontal sandstones can 

 be traced to tjjeir exact junction with the southward-dipping traps. But, in 

 several places, the sandstones present a very remarkable change as the trap is 

 appi-oachod. On passing up the gorge of Black River, whose sides are perpen- 

 dicidar exposures of rock over one hundred and fifty feet in height, towards 

 the south, the horizontal layers of sandstone are suddenly seen to change from 

 their ordinary position to a confused mass of broken layers, dipping in every 

 conceivable direction, and increasing in confusion as the trap is approached, 

 until, finally, the whole changes to a confused breccia of mingled trap and 

 sandstone fragments. This appearance is presented along both sides of the 

 gorge, for a distance of 300 feet, and I am assured by my assistant, Mr. E. T. 

 Sweet, by whom all observations in Douglas county were made, that it is cer- 

 tainly due to no mere surface misplacement. The same appearance is pre- 

 sented on one of the other northward flowing streams in Douglas county, on a 



