D. H. Browne — Phosphorus in Iron Mtn., Mich. 301 



shows this very plainly (fig. 2). A horizontal cross section of 

 several small veins shows that the hanging wall curves toward 

 the foot. On large- veins the strata have been subjected to so 

 much flexion that this curvature is not clearly seen, but on 

 small veins it is unmistakeable (see fig. 1, a). I must here state 

 that in the greater number of veins on the Menominee Range 

 the dip is to the south, and hence what is called the hanging 

 wall in the Chapin and Ludington Mines answers in them to 

 foot wall. If we attempt to make an ideal vertical longitudi- 

 nal section of the ore deposits it seems to have the shape given 

 in figure 3. A study of the eastern and western limits of the 

 Chapin Mine seems to verify this idea. Figure 18 shows a ver- 

 tical longitudinal section of a small vein in which this shape is 

 very noticeable. The ore will now be understood to lie in the 

 form of lenticular deposits dipping north, and pitching west. 

 With regard to the content of phosphorus : the first thing- 

 noticeable was that if a room, in stoping up, changed from 

 non-Bessemer to Bessemer ore, such change was liable to occur 

 at the footwall side of the room. In making maps of those 

 rooms in which change occurred it was also noticeable that the 

 ore at the eastern end of the rooms was higher in phosphorus 

 than that at the western end. The most typical room was No. 7 

 Room, 2 Shaft, 5th Level, which is outlined in figure 4. This 

 room was, if I remember aright, about 3^ sets from east to 

 west and four sets from footwall to hanging. A set, I may say, 

 is a space 8 by 8 by 8 feet, outlined by the timbers used to sup- 

 port the back. From the ground plan of this room it will be 

 noticed that the ore showed a marked regularity of formation. 

 Follow the course of the hanging wall, and trace the increase of 

 phosphorus from -068 at the west hanging wall set to "078, 086, 

 •100 and finally "156 on the east hanging wall set. Such increase 

 is also noticeable in the ore in entry from '060 to *096 and, 

 though less plainly on the footwall from *020 to '032. Beside 

 this regularity there is a corresponding increase from footwall 

 to hanging. Notice the gradual change from *032 and "028 on 

 the foot, to '045 and *040 in the middle and \L56 and "068 on 

 the hanging wall. On inspection, figures 4 to 16 will also show 

 the same peculiarity and a large number of average analyses 

 corroborate the conclusion that in this mine, as a rule, the ore 

 increases in percentage of phosphorus from footwall to hang- 

 ing wall, and generally speaking from west to east. It fre- 

 quently happens, however, that a streak of high or low phos- 

 phorus ore crosses a room from west to east, as in figures 4, 14, 

 and 15. This seems to be due to the fact that one or more in- 

 dividual layers of ore were originally very high or very low in 

 phosphorus, and such individuality has not been observed by 

 subsequent changes. Moreover irregularity is very frequently 



