CORE ORIENTATION 



71 



it produces a core — Thurmann's apparatus is certain in 

 action, since here shocks cannot bring about preliminary 

 disturbance of the needle, a factor which is not provided 

 for in Heine's apparatus. The internal construction of the 

 apparatus is much simpler and the arrest of the needle 



^ 



^■5+ 



It 



Bronze 

 Rods ^ 



73 cm.' 

 long [ 



Fig. 36. — Thurmann's stratameter. 



Fig. 37. — The North German Deep 

 Boring Co.'s stratameter. 



occurs much sharper than in Meine's device, because the 

 transmission of the arresting action takes place by means of 

 only two pieces of mechanism and not by means of a series 

 of intermediate members. 



The North German Deep Boring Company's Strata- 

 meter. — The North German Deep Boring Company of 

 Nordhausen have produced a device of the stratameter 



