146 DEEP BOREHOLE SURVEYS AND PROBLEMS 



The instrument we have had the advantage of examining 

 was suited to a 4-in. borehole and was about 35 lb. in weight, 

 40 in. long and had %6-in. walls. It is efficient and 

 certainly cheap and convenient and has been tested for an 

 external pressure of 600 lb. per square inch. 



Kegel's Apparatus. — This is an ingenious floating 

 plunger plumb-bob device invented by the mining engineer 

 Karl Kegel of Freiberg in Saxony in 1919^ and capable 

 of many alternate constructional rearrangements and 

 modifications. 



It gives the apparatus at the place being surveyed a 

 definite direction from which it cannot deviate. In Fig. 

 1 (Plate X) the heavy rod h or chisel c or both are attached 

 to the main rods a as also are guide devices d and plumbing 

 medium e. The action of the last named will be seen 

 from sections EF and CD, it being premised that other 

 constructions of plumb and connecting tubes will attain 

 the same end. The plumb g here floats in the plumbing 

 fluid h and has a bottom plunger carried through the guide 

 i SO that as a result of the buoyancy it always floats upright 

 over the guide hole. The upper plunger of plumb g pro- 

 jects through three contacts j, k and I and lies against a 

 particular contact should there be any borehole dip. The 

 guide casing recess belonging to the particular contact 

 concerned has its own electric motor and current supply. 



There are thus three of these, one for each of j, k and I. 

 The motion of any one motor is transmitted by a worm and 

 worm wheel m on spindle n. The wheel and spindle are 

 connected by spring and groove in such a way that the 

 spindle may move axially through the wheel. The spindle 

 passes through the fixed nut o on the housing or casing d 

 and is displaced according to how it is rotated. With 

 similar rotation any two given motors will turn back 

 accordingly and so displace their spindles backwards. 

 Thus the spindles act as centering screws. On being let 

 into the hole the three motors with special supply current 

 may be so switched in as to draw in their spindles and 



1 German Patent No. 317,663. 



