Miscellaneous Subsurface Methods 



593 



rel is surmounted by a horizontal pin. A nonmagnetic drill collar is used 

 directly above the core barrel, in order that a single-shot instrument may 

 be used to ascertain directions. An Eastman single shot is used in a spe- 

 cial barrel, the bottom of which is equipped with a mule-shoe device, which 

 fits accurately over the end of the inner barrel shaft and engages the pin. 

 The surveying instrument is slidably mounted within its barrel, so that it 

 may be shock absorbed without changing position with respect to its longi- 



r 



LOW SIDE 

 OF HOLt 



^»»* 



^LmmnQ bus 



"*?» 



^Sm 



Figure 307. Core-orientation reader. 



