. Deep borehole surveys and problems. Boring. 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
. Deep borehole surveys and problems. Boring. 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, Fig. 51.—Riihland's Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloratio
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