SEISMIC METHODS 



865 



clear holes the charge is lowered by the cap wires and care is taken to avoid 

 damaging the wires during loading. After loading into a dry hole, it is 

 desirable to confine the charge by filling the hole with water to a level well 

 above the top of the charge. Figure 539 shows an approved procedure for 

 loading shot-holes. 



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Fig. 538. — Method of assembly to prevent strain on cap wires. 

 A, cartridge of explosives; B, cap wires; C, half hitch loop to take 

 strain. 



Safety Practices in Loading Procedure.* — Charges should not be 

 made up prior to loading in the shot hole. 



Caps must not be removed from the magazine until the charge has been 

 made up and is ready for lowering. The shooter should then take the cap, 

 attach it to the charge, and immediately lower the charge to the predeter- 

 mined depth in the hole. The leads should then be taken to the blasting 

 box. When personnel and equipment are safely located, the leads may be 

 attached. The shooter should give three safety checks to the operator before 

 firing, and must not fire until authority is received from the operator. 



Magazine doors should be closed at all times except when removing 

 explosives. 



* The author is indebted to A. G. Munro, Aetna Life Insurance Company, Los 

 Angeles, CaHf., for many suggestions regarding safety practices. 



