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



attempt to outline the curvature of isocliemic lines in the 

 course of 5 shaft from the surface to the 8th level. I have 

 in my possession detail maps of the chemistry of the entire 

 course of No. 5 shaft, showing the percentage of phosphorus 

 in every eight feet cube of ore removed. As it would be 

 impossible to reduce this map to the size of the engravings 

 required for an octavo page and preserve at the same time 

 the clearness of the figures therein, I have been obliged 

 in drawing Maps 18, 19, 20 and 21, to omit more than two- 

 thirds of the figures in the original drawings. Figure 23 

 will be understood then, simply as an outline sketch. By 

 actual measurement the distances along various levels, through 

 which certain average percentages of phosphorus obtained, 

 have been carefully ascertained, and the exact points where 

 change from Bessemer ore to non-Bessemer occurred located 

 upon the section map to correspond. The curvature of the 

 isochemic lines, therefore, is in accurate correspondence with 

 the course of high and low phosphorus throughout the western 

 end of the Ludington mine. The drawing of various rooms 

 and pillars is in this map omitted. The curving lines, when 

 close together, represent high phosphorus ore ; the arrows in- 

 dicate direction of Bessemer ore ; and the figures represent 

 averages of several hundred analyses for phosphorus taken in 

 the immediate neighborhood indicated thereby. 



From this figure (23) it will be noticed that on the upper 

 levels the greater portion of the ore is non- Bessemer. At the 

 west end of the mine, a small streak of Bessemer ore follows 

 the shaft, gaining toward the west until the 4|- and 5th levels 

 are reached, where the Bessemer ore flexes toward the east and 

 merges into the broad current of first-class ore which flows 

 upward and eastward from the lower levels of 5 shaft. The 

 non-Bessemer ore follows the western boundary of rock, and 

 seems to accumulate also in shoals outlined by projections or 

 intrusions of jasper, which break the flow of the current. 



On stoping up No. 1 Room, 7th Level, through ore gradually 

 increasing in phosphorus, a seam of rock was encountered. 

 As analysis of the drift over head had shown low phosphorus, 

 and the shaft 50 feet to the left had passed through Bessemer 

 ore, I concluded that the ore above this rock would be of 

 first-class quality. This prediction was made entirely on the 

 supposed consistency and continuity of isochemic lines, as no 

 ore had been taken from above this rock for analysis. I was 

 at this point called to New York on business, and before leav- 

 ing, left word with the mining captain that any ore found 

 above this rock should be sent up for first-class ore. On re- 

 turning to the mine three weeks later I found that this rock 

 had been pierced and some 200 tons of ore from over head 



