192 



DEEP BOREHOLE SURVEYS AND PROBLEMS 



as a whole, and in such cases mechanical means must be 

 used. 



The Mechanical Guide of the Rods. — The above-mentioned 

 rods of stiff members with cross links are movable on all 

 sides in their long axis but not at all in the cross direction, 

 so that they can follow a winding hole without losing their 

 orientation. Thus the borehole course is resolved into 

 short pieces. The correct working of these guides is an 

 important preliminary of all surveys. Trial of rods 

 through 180 deg. before every test is considered a good 

 check. 



Fig. 132. — Borehole survey by Haussmann's method. 



In plumbing a hole in undisturbed conditions, first 

 arrange marks for depth measurements on the rope or 

 use a measuring wheel, or, if using rods, mark the rods for 

 a given direction on the scale of the registering apparatus. 

 Now when ready switch in the resistance for the lamp and 

 solenoid and read with the ammeter and voltmeter. The 

 first survey is made with the plumb cyUnder hanging 

 free in the hole. By means of the switch lever we can 



