840 



EXPLORATION GEOPHYSICS 



A full set of reels containing seismometer and telephone cables are 

 fastened to the truck. The number of reels and the arrangement of cables 

 vary considerably among operators and depend upon such factors as 

 number of seismometers, length and type of spreads, provision for varia- 



FiG. 524. — A fully-inclosed type of seismic recording truck with power- 

 driven reels and four-wheel drive. A, door to instrument compartment; B, 

 reel compartment; C, seismometer and other storage; D, drinking water. 

 (Courtesy of Western Geophysical Company.) 



tion in spreads, efficiency in disposing and picking up of seismometers, 

 and preservation of cable. The number of reels varies from two to eight 

 or more. To avoid great cable strain, the cable often is reeled-in while 



Fig. 525. — Auxiliary service truck. A, power driven reel for extra cable; 

 B, motor drive; C, clutch and brake levers; D, box for spare seismometers; 

 E, space for tool box, etc. (Courtesy of Griffin Tank and Welding Company.) 



the truck is driven along side of the cable. In any case, at no time should 

 cables be pulled with such force as to harm the conductors, particularly 

 the splices and connectors. 



Figure 525 shows an auxiliary service truck, which usually supplements 

 the recording truck. It is equipped with a power-driven reel and brake 



