198 



DEEP BOREHOLE SURVEYS AND PROBLEMS 



tube withdrawn sufficient to expose the controller, which is 

 set for the desired number of records and required interval 

 between time of setting and first exposure. The watch 

 of the operator is synchronized with the instrument clock 

 and the whole apparatus assembled, screwed up tight, and, 

 with the insulation rod attached to the instrument, lowered 

 to the spot to be surveyed. Depth and time are noted, 

 and time for exposure at the spot exceeded, it is lowered 

 to the next spot and so on for the number of spots being 



C.L.of Clinomeier 

 Drum Spindle 



OLrtsideFrontViewof Clinometer Apertures 



30° 



Nol- 



-fJo.l 



No.2- ■=- 

 (Datum) ' 



A/o.2 

 ■No.2 i 



Jo I 



45° 



45 



90 



(a)| I (b)| I I |Cc) 



Topical Record 



showing progressive 



increase in Dip 



Fig. 135. — Clinometer record. 



surveyed, after which the instrument automatically ceases 

 working and is withdrawn from the hole. It is now taken 

 to the dark room where the record strips are withdrawn and 

 developed. 



Assuming that the instrument is horizontal and the con- 

 troller end points toward the magnetic north, which is 

 datum line direction, we get a record as in Fig. 134a. 

 If the said end be pointed northeast, the record is as in 

 Fig. 1346; if southwest, it would be as in Fig. 134c, the dis- 

 placements being typical for these positions. The drums 

 are designed so that 300 deg. equals 3.6 in. on the record 

 strip surface, or 1 deg. equals 0.01 in. Thus by dividers 

 and a diagonal scale we may read hundredths of an inch, 



