168 



DEEP BOREHOLE SURVEYS AND PROBLEMS 



The apparatus itself is in three distinct elements; the 

 transmitter for the base of the borehole, the surface 

 receiver connected electrically to the transmitter, and the 

 lowering rods with orientation couplings. 



The transmitter is a strong, pressure-proof, steel tube 

 with a pendulum, the trajectory grid plate and the electrical 

 connections inside. The pendulum^ (Figs. 104, 104a) 



Fig. 104.— The Denis-Foraky tele- 

 clinograph pendulum. 



Fig. 104a. — The Denis- 

 Foraky teleclinograph 

 pendulum. 



has a Cardan suspension at A the functions of which are 

 resolved in an elastic system made up of two crossed springs 

 (Fig. 105). The system has the property of acting in 

 such a way that the instantaneous centers of rotation of the 

 pendulum may be taken as coincident with A. The pendu- 

 lum is not allowed to swing freely under the force of gravity. 

 No two similar double systems constitute a suspension 

 without play or friction, and this method of construction 



1 Haddock, M. H., "Location of Mineral Fields," p. 92, Crosby, 

 Lockwood & SonSj London. 



