SEISMIC METHODS 



869 



inside surfaces of both the trailer and the magazine are lagged with a 

 double thickness of one-inch oak, the grain of the wood in each layer being 

 laid at right angles. Spuds are provided at all four corners of the trailer; 



Fig. 543. — Shooting truck and shot-point geyser, a, water tank; h, explosive 

 compartments. 



Fig. 544. ■ — Powder magazine trailer and cap magazine. A, 

 trailer; B, spuds, retracted; C, spud, in position; D, double oak 

 planking; E, cap magazine; F, lock shield. (Courtesy of GriiBn 

 Tank and Welding Service.) 



they are retracted when the trailer is being handled. A hole in the bottom 

 of the magazine allows it to be bolted or anchored to prevent theft. Heavy 

 sheet-iron shields are placed over the padlocks to protect the locks from 

 tampering. 



