306 D. 11. Browne — Phosphorus in Iron Mtn., Mich. 



the footwall, all seem to indicate that the ore was deposited 

 in hollows of the exposed slates which now form the hanging 

 wall. Furthermore since it is well understood that the almost 

 uniform tendency of all deposits east of the Mississippi River 

 is in a hue from southwest to northeast, it is very probable that 

 this deposit, as originally laid down, was no exception to the 

 general rule. If we suppose that the ore was formed in hollows 

 in the hanging wall, and was covered by the footwall slates, 

 and that this bed has been tilted up from the north side, 

 through an angle of 100° to 110°, it will be readily understood 

 that the original trend of the deposit becomes the complement 

 of the. present pitch of the ore. This supposition explains 

 also the strike of ~N. 75° W., and the fact that what is now the 

 hanging wall seems to have been the original bed of deposit. 

 It is improbable that the tilting has been from the south side 

 upwards through an angle of 70° to 80° ; for if this had been 

 the case the ore would pitch east at the same angle at which it 

 now pitches west. 



In the American Journal of Science for January, 1889, Pro- 

 fessor Yan Hise suggests that the soft ores of the Gogebic 

 range have been formed by the action of percolating waters 

 containing carbonic acid, which, acting upon previously de- 

 posited carbonate of iron, has dissolved iron therefrom ; and 

 this dissolved iron has been precipitated by oxygen-bearing, or 

 alkaline waters from the surface. This theory, while seeming 

 to explain the formation in the Gogebic mines studied, seems 

 less probable as applied to the mines on the Menominee Range. 

 Here the ore rests directly upon clay slates containing none of 

 the unaltered carbonates found in the Gogebic Range. The 

 ore also lies not in trough-like formations, but in regular basins 

 of lenticular shape. The ore exhibits none of the nodular 

 form spoken of in Professor Yan Hise's paper, and the strati- 

 fication is remarkably even and regular. 



The suggestion made by Mr. R. D. Irving in the American 

 Journal of Science for Oct., 1886, that the ore has been washed 

 into its present position from previously precipitated beds of 

 carbonate, seems to me very plausible, and is borne out in a 

 large measure by the chemistry of the ore body. I should, 

 however, suggest this change, that the original deposits of iron 

 and lime were not as crystallized siderite and calcite, but as 

 hydrous oxide and carbonate of iron with intermixed calcareous 

 deposits. This finds analogy in the formation of beds of bog 

 iron ore in the present day. It is worthy of note that such 

 beds of altered bog ore do exist in the Huronian strata repre- 

 sented in the upper Peninsula of Michigan. Any one familiar 

 with the non-Bessemer ores of the western end of the Meno- 

 minee Range must have been struck with the remarkable 



