100 



DEEP BOREHOLE SURVEYS AND PROBLEMS 



Among the principal disadvantages of the apparatus are : 



1. In hot strata special cooling devices have to be 

 employed and they interfere with the efficiency of the 

 method. 



2. In holes varying in direction of deviation and subject 

 to concussion of the rods there is the likelihood of there 

 being several etched marks which give rise to confusion. 



3. The apparatus can only make intermittent surveys 

 and cannot be arranged for continuous reading down the hole. 



Riihland's Apparatus. — This device was invented to 

 obviate the confusion of lines arising from several acci- 

 dental markings, as under 2 above. ^ In this method a 

 colored fluid was let down the hole in a 

 special chambered container and means 

 provided for emptying the same while 

 a magnet was employed to give the 

 direction of deviation. 



In Fig. 51 the apparatus will be seen 

 to consist of four chambers 1, 2, 3, and 

 4 under one another and connected by 

 valved orifices. The chamber 3 is made 

 of glass and the others of a non-mag- 

 netic material. Chambers 2 and 3 can 

 be shut off from the others by means of 

 the valves Vi and V2. Valve V2 extends by 

 a rod a up into chamber 1 where it sup- 

 ports a needle n and has a band bi. A 

 tube t is screwed about rod a also project- 

 ing up into chamber 1 and ending in a 

 band 62- Valves wi and V2 are pressed by 

 springs Si and S2 and remain fixed on their seats as long as 

 the angle arresting hooks Ci and c^ are not actuated by the 

 coils di and d2. The induction coils di and d2, of which Ci 

 and C2 are cores, when uncharged with current from the line 

 leading up to the surface, keep the hooks and therefore 

 the valves shut. The two current lines from the coils go 

 insulated in the same cable to bank but are completely 



1 German Patent No. 148,068. 



Fig. 51. — Riihland's 

 apparatus. 



