274 



LOGGING 



being taken not to pull the cap out of the primer. If the car- 

 tridges are used in wet places soap or tallow is smeared over 

 the safety fuse at the point where it en- 

 ters the cartridge to prevent the entrance 

 of moisture into the blasting cap. 



Some persons prefer to use the method 

 I of attaching caps shown in Fig. 76, b. 

 1 A hole is punched in the side of the 

 I cartridge with a sharp wooden stick 

 c and the fuse attached as shown. This 

 Fig. 76. — Method of placing method is satisfactory because the fuse 

 Caps in the Primer, a, and comes against the side of the bore and is 

 b are for firing with safety, ^^^ ..^^^ ^^ disturbed by the tamping 

 fuse, c, for firing with an •' i 1, , r 



electric battery, d, shows bar, and the cap cannot be pulled from 

 the cap ready for the in- the primer and thus cause a misfire, 

 sertion of the fuse, e, cap pj-i^ers are placed on top of the 



with fuse inserted and the , , • i i , r 



cap shell crimped. charge, but m deep holes, manufacturers 



recommend that additional blasting caps 



without fuse be placed at 5-foot intervals throughout the charge. 



Electric Fuse. — When it is desired to fire several different 

 charges at one time electric fuses are used in connection with a 

 battery. They consist of two wires inserted in a cap containing 

 a mixture of fulminate of mercury and potassium nitrate or 

 chlorate. The open end of the cap is plugged with sulphur. 

 The fuses are adjusted as shown in Fig. 76, c. When an electric 

 fuse is used the primer is often placed in the center of the charge. 

 The practice in electric firing is to separate the two wires on the 

 fuse and connect one to a wire on a charge on one side and the 

 other to one on a charge on the opposite side. The entire set 

 is connected up in this manner leaving one free wire extending 

 both from the first and the last hole. The two leading wires, 250 

 feet or more in length, are then connected to the above wires and 

 carried to some protected point. When all is in readiness the 

 leading wires are attached to the poles of the battery and the 

 charge fired by an electric firing machine. 



Tamping. — Tamping should always be done with a wooden 

 bar, never with a tool having any metal parts, and the tamping 



