1056 



EXPLORATION GEOPHYSICS 



S.P. and the resistivity parameters are recorded on a sensitized film. The movement 

 of the film is synchronized with the cable, so that a definite ratio exists between a unit 

 of length on the film and a unit of length along the bore hole. For example, scales of 

 1", 2" or 5" of film to 100 feet of cable are available. Synchronization of film and 

 cable may be accomplished by use of two interlocking synchronized motors, one being 



Fig. 652. — Measuring sheave wheel for electrical logging, a, supporting hook 

 fastened to traveling block; b, weight spring; c, weight selsyn motor; d, cable to record- 

 ing truck; e, cable guides; /, footage selsyn motor; g, selsyn drive gear; Ii, cable con- 

 nections to selsyn motors; i, bail for tie-back chains; ;', ground manganese steel sheave 

 rim for measuring cable. (Courtesy of Lane-Wells Company.) 



geared to a sheave or measuring wheel frictionally contacting the cable, and the other 

 to the film drive (Figure 652). The ratio of film to cable speed is varied by changing 

 the film-drive gears. 



The S.P. and the resistivity recorders are of the general type previously described 

 in connection with seismic exploration, with depth markers substituted in place of 

 time markers. 



