98 



DEEP BOREHOLE SURVEYS AND PROBLEMS 



2. With some fluids capillarity effects are harmful to the 

 readings, especially in small diameter boreholes. 



3. Turning of the apparatus in the hole either on going 

 down or on being raised out nullifies the direction results 

 but not the amount results for inclinations. 



4. The centering of these devices is usually neglected. 

 Nolten's Method. — The oldest method applying the fluid 



principle is probably that introduced by G. Nolten, a 

 district counselor of Dortmund in 1873.^ 

 Hydrofluoric acid is used as the fluid which 

 eats an outline at its surface on a glass 

 cylinder. The direction of the deviation 

 is obtained from a clockwork arrested 

 magnetic needle in a cylinder fixed to the 

 fluid vessel. 



In Fig. 48 is shown the vessel of colorless 

 glass having an exactly cut base with per- 

 pendicular walls. If the vessel is half filled 

 with dilute acid and left about half an hour 

 in an inclined position we get the etched 

 mark ah (Fig. 49). If we now lay the vessel 

 horizontal we get another mark cd. If we 

 draw a parallel to dc through a, then in the 

 triangle ahf resulting we know sides af and 

 hf so that angle haf can be determined. 



In the hole the glass vessel is encased in 

 a watertight, sealed measuring cyhn- 

 der c. This is connected by a screw 

 spindle I to the rods or rope (the whole internal part can 

 be extracted from the shell on this spindle). Gutta- 

 percha discs a and ai guard the apparatus against concus- 

 sion shocks. The top opening of the measuring cylinder 

 has three notches 60 deg. apart which are for fitting on 

 three corresponding plates X, Y and Z. After putting 

 in the plates they are locked fast by a 60-deg. turn. The 

 locking screw goes through plate X. On the lowest plate 

 Z stands the glass cylinder c which has a fixed graduation 



1 See also Redmatne, R. A. S., Vol. 1, and Pr. Zeitschrift., Vol. 27, p. 176. 





Fig. 48. — Nolten's 

 apparatus. 



