CORE ORIENTATION 



59 



grip, preventing sliding. In action the lowering tool holds 

 trigger h out. At the core and after sufficient time has 

 elapsed and the needle has come to rest, the lowering tool on 

 being withdrawn releases the trigger h, throwing the catch g, 

 allowing/ to ascend and lift the card off its bearing, pressing 

 it against the glass lid c. 



The core is now wrenched off and lifted to bank and on 

 unscrewing lid h the orientation of the core is read. The 

 weaknesses of the apparatus are the 

 same as those of Vivian's apparatus; 

 chiefly insufficient protection against 

 water pressures which is more necessary 

 here, since there are more moving parts. 

 The drawbacks of space demands in the 

 core and trouble in the measuring 

 method have not been removed any 

 more than in Vivian's method. Again 

 there is the liability of premature dis- 

 turbance of the needle due to shocks as 

 in wrenching off the core. There appear 

 to be as little data in professional 

 literature respecting its actual employ- 

 ment as in the case of Vivian's apparatus. 



Wolff's Apparatus. — This device was 

 invented in 1889,^ and marked the 

 introduction of a new feature. In this 

 method the apparatus was lowered ^^° 

 over a stub of core in the hole and 

 a mold taken. Clockwork was used 



////////// r // y///. 



32.— Wolf's core- 

 cast device. 



to 



clamp a 



magnetic needle after a predetermined time. The core 

 was then removed and orientated from the clamped 

 needle attached to it. Figure 32 shows Dr. Wolff's method 

 for fixing the compass in a mold or cast, the latter being a 

 plastic material. The apparatus consists of a two-part 

 tube A1A2, with a lead filling B, which serves to guide and 

 hold tight the lower plastic mass giving the imprint of the 



1 See German Patent, 47, 221, Oct. 27, 1888; also Osterr. Z. Berg-Huttenw., 

 Nos. 41-43, 1906. 



