SEISMIC METHODS 



867 



Flu. 5-HJ. — Method of loading explosives in a nicdiuni depth 

 hole for seismic work, a, explosive cartridge; b, firing wires; c, 

 spear or "schnozzle"; d, loading pole; e, extensions with link 

 couplings. (Courtesy of United Geophysical Company.) 



through "bridges" of material. The time re- 

 quired for loading deep holes is greatly de- 

 creased over that required for loading by use 

 of hand poles. 



Another method of loading deep holes uses 

 a device similar to the "spoon," except that the 

 charge is pushed to the desired depth by a 

 weight. However, experience has shown that 

 it is easier to pull the charge down than to push 

 it. To accomplish this, a heavy wire is securely 

 attached to the explosive column and bent into 

 a hook at the bottom of the column. This hook 

 is inserted into a recess in the weight. Thus the 

 force is applied at the bottom of the column, 

 and as the weight is lowered into the hole the 

 explosive charge is pulled to the desired depth. 

 When the weight is raised the charge is left 

 behind. 



The character of the record is influenced by 

 the depth and size of shot. Each area behaves 

 somewhat dififerently and the sound of the 

 explosion frequently is indicative of the shot 

 characteristics. Generally, a mufifled or dull 



Fig. 541. — Aluminum link- 

 connectors for loading-poles. 

 (Courtesy of Century Geophysical 

 Company.) 



