SOUDAN FORMATION. 239 



falls prevented by breaking- down the rock as soon as it is observed to 

 be loose. From tlie top of the fill the roof can readily be reached and a 

 slice of ore about 10 feet in thickness is blasted down from it, broken 

 Ujj, and thrown into the chutes (mills). These chutes are 25 feet apart. 

 Formerly they were much more widely separated, but exjoerience has 

 shown that the distance now maintained is the best. The men han- 

 dling the ore which falls between can work both ways from the chutes 

 and can throw the ore into the chutes without tramming or second 

 handling. These chutes lead down to the drift below, and from them 

 the ore is let out into the tram cars. PI. X, A shows the method of 

 loading these cars in the main drift at the bottom of one of the chutes. 

 When filled the cars are hauled by mules to the shaft and thence hoisted 

 to the surface. As the stope is extended filling is let in from the raises, 

 and the chutes and ladder ways are extended upward to keep pace with 

 the filling. 



The ore is very hard and the cost of breaking it is high. Percussion 

 or power drills are used to some extent, but diamond drills are more com- 

 monly used for boring the holes which are used in blasting the ore down. 

 Tljis is probably the only mine in the district in which the diamond drills are 

 used for boring preparatory to blasting. It has been found that diamond 

 drills are in the long run cheaper for this work than percussion drills. 



After having been hoisted to the surface the ore is run through Blake 

 crushers, which reduces it to sizes suited for furnace use. The ore is then 

 run directly into cars during the shipping season, or during the winter 

 season is piled in stock piles and loaded from these by steam shovels into 

 cars when the shipping season begins. 



The ore deposits at Ely are the most important and most interesting 

 in the district. The oldest and most productive mine at Ely is the 

 Chandler, in which the ore is mined on the caving system. The great 

 body of ore that is exposed by the Chandler lies in a trough of greenstone 

 which pltmges to the east at an angle of about 45°. The continuation of 

 this same ore body is worked on the caving system by the Pioneer mine to 

 the east of the Chandler, which, since it is on the pitch of the ore body, 

 gets all of the water from the Chandler. A layer of sheared greenstone 

 discolored by iron (paint rock), 20 to 22 feet thick, lies between the ore and 

 the comparatively massive greenstone. The foot and hanging walls of this 



