238 



THE VEKMILION IRON-BEARING DISTRICT. 



from level to level with the bottom of the open pit. Such a raise passes 

 through a level with its front face cribbed and an opening in the raise at 

 the height at which it is desired to discharge the filling into the trams 

 waiting for it. When filling is desired at any place the entire raise below 



that point is filled, and the filling 

 then run through the opening in the 

 cribbing at the proper place; or tim- 

 bers and rails may be laid across 

 the raise, making a floor, which pre- 

 vents the filling descending below 

 that point, and from this place it is 

 then run out into the trams. 



Rock to fill the topmost level, 

 or any other level being worked at 

 the same time with it, is taken from 

 the accumulations of loose material 

 at the bottom of the open pit, de- 

 rived from the caving in of its sides 

 and from the drift at its surface, or 

 else from material which has been 

 blasted down from the walls of the 

 pit. After the topmost level is 

 worked out filling may be run down 

 into the level below that, and so on 

 down as the development requires it. 

 Fig. 16 is a cross section through the 

 Minnesota mine showing how the 

 raise in the foot wall connects with 

 the surface, and how connection is 

 maintained with the levels at various 

 heights as the filling proceeds. 



Upon this filling the workmen 

 stand, and here the di-ills are placed, mounted on braced cribbing, or in 

 any other way that will give them a sufficiently firm foundation. This 

 keeps the workmen near the roof, which is one of the advantages of over- 

 hand stopiug, in that the roof can be easily examined and accidents from 



■Cross section of Soudan mine showing raise. 



