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EXPLORATION GEOPHYSICS 



the traverse line at the desired distance apart. By means of insulated 

 handles, provided with spring contact clips, electrode men stationed at 

 2 and 3 connect the electrodes A and B, respectively, with the lead wires. 

 The flexible lead wires connecting the reel terminal box with the electrode 

 handles are of equal length, and this length is approximately the distance 

 which the electrodes are to be placed along the traverse line. The operator 

 stationed at 1 slowly moves the reel forward; after a certain distance has 



Fig. 319. — Electrical connections for semi-continous electrode system. (Courtesy of 

 International Geophysics, Inc.) 



been traversed, the flexible wire connecting the rear electrode A becomes 

 taut and continuous movement forward of the reel pulls the clip from the 

 electrode. At this time the operator stationed at 2 walks past the operator 

 at 3 and makes contact with the next electrode C. The operator stationed 

 at 4 removes electrode A from the ground and drives it into the ground 

 on the traverse line beyond electrode C, at the desired spacing. As the reel 

 continues to move forward, electrode B will automatically become discon- 

 nected, and the same procedure is repeated. By this procedure, one ground 

 electrode, then two, then one again, and so on, are always connected to 

 the recording equipment. 



This system of semi-continuous electrode movement necessitates con- 

 tinuous recording equipment similar to that employed for the continuous 

 contact mobile electrode. The position of the reel is signalled to the 

 recording truck by the operator stationed at 1 who closes a key switch 

 each time the reel comes abreast of an electrode. These signals are 

 recorded at the instrument truck in a manner similar to that employed 

 for the continuous moving electrode. The method requires at least five 

 operators for satisfactory operation. In areas of rough terrain, an addi- 

 tional operator may be required for handling the reel. With sufficient 



