i86 



ENGINEERING ON THE FARM 



be due to frozen dynamite, grounding of the circuit, short 

 circuit, or the breaking of the platinum bridge of the cap by 

 rough handling. In case of failure in electric firing the first 

 step would be to disconnect from the fuse wires and test the 

 electric circuit. Where necessary to use a new primer the 

 tamping may be removed down to within 3 or 4 inches of 

 the charge and another placed, tamped, and fired. Both 

 charges will explode unless the dynamite is frozen. 



Frozen dynamite. Dynamite freezes at from 42 ° to 50 

 Fahrenheit and should not be used when in this condition. 



After E. I. du Pont de Nemours & Co. 



Fig. 168. Electric firing connected in series 



It is hard to detonate and ordinarily does not have its full 

 strength. When frozen, the sticks are hard and rigid. If 

 properly thawed the explosive is not injured by the freezing, 

 but where large quantities of dynamite are to be used 

 provision should be made to keep it where it will not freeze, 

 or it should be used before it has time to freeze. When 

 it is necessary to thaw dynamite, it should be placed in a 

 water-tight vessel set in another vessel containing warm 

 water. The water in the vessel should be a few degrees 

 above the freezing point of the dynamite, but not at the 

 boiling point. Sticks of dynamite can also be thawed by 

 being laid on a shelf in a warm room over night. Under 

 no conditions should it be placed in hot water, in steam, 

 in an oven, or before an open fire. Frozen dynamite is 



