SOUDAN FORMATION. 241 



instead of 75 feet, and no subdrifts are used. The intermediate main di'ifts are of 

 the regular size, 9-foot caps and 7-foot legs, which leaves about 10 feet of ore to be 

 caved, instead of 7 to 8, as before. Stations are made at the shaft for each inter- 

 mediate main level. Under this modified sj^stem the removal of each 20-foot block 

 will be done as before, but the putting up of raises will be saved, and it is intended 

 to use cars and thus do awa_v with wheelbarrows as far as possible. 



PL X, B, shows a main drift which has begun to cave under the 

 weight caused by the wrecking of the subdi-ifts just above. PL XI, 

 shows the miners removing- the ore from a part of the mine where the 

 caving has taken place. 



The ore mined by the Chandler is good hard hematite, practically as 

 hard as the Soudan ore. Subsequent to its formation (p. 233) it was frac- 

 tured by the orogenic forces which folded the rocks, and it was thereafter 

 not completely cemented. A more complete healing of these fractures 

 seems to have taken place in the ore exposed by the workings of the Savoy 

 mine (old Section 26 mine), at the eastern end of the Ely trough. The 

 caving' system described above, as followed in the Chandler mine under 

 Manager John Pengilly, takes advantage of the fracturing which already 

 exists in the ore and carries it farther through the pressure of the super- 

 incumbent load. As a result, the mass of ore obtained in this way is very 

 much brecciated, so that it can readily be broken up by picks. In conse- 

 quence of the ease with which it can be obtained by picking, the ore is 

 frequently erroneously spoken of as a soft ore. The individual pieces of 

 the breccia, it must be borne in mind, are, however, the hard hematite, 

 nearly as hard as that of the Soudan mines. In driving some of the 

 headings, where the caving has not affected the ore, machine drills are 

 very frequently employed. 



PRODUCTION AND SHIPMENTS OF IRON ORE FROM THE VERMILION DISTRICT. 



The following tabulated statement gives the annual production and ship- 

 ments of iron ore for the Vermilion district and the totals for the district 

 since the date of the first shipment (1884) up to the present. The figures 

 for the annual production during the early years of the mines were not 

 obtainable, but have been given as a lump sum for those years. The figures 

 have been compiled by the Minnesota Iron Company, and are the most 

 accui'ate that can be obtained. 



MON XLV — 03 16 



