FLUID METHODS OF SURVEYING BOREHOLES 



115 



in Fig. 62) closely fits the inside of the glass tube. At the 

 top the tube narrows into a neck with a threaded ring 

 joining the glass tube with the cathode. 



Fig. 62. 



The registration apparatus is enclosed in a steel tube 

 fitting closely in the hole and the registrations are made as 

 follows : 



The zenith angle 6 is obtained by noting the greatest 

 {h^^J and the least {h^.^J heights of the precipitation on 



Three phnes, ^BC, ACD. and BCD are all af right 

 angl&io each other. 



Angle BAC - 0, Angle DAC = ©j 



A plane through A, B and D corresponds to the fluicf 

 ^surface. 



The line A -£" corresponds to the great axis 

 and ihe angle D Ct is the apsidal angle ff> 



Tan V> = -r T- — 



^ "l&O-l-'O 



Fig. 63. 



the cathode cylinder (Fig. 63) and it is found from the 

 relation 



h — h 



tan 6 



max ' mm 



d 



(9) 



where d is the diameter of the cathode. 



