PHOTOGRAPHIC METHODS 



187 



der. On the right is an accumulator with cells and on the 

 left, on the tripod, a current switch connected to the accu- 

 mulator and coupled to the cable reel. 



The 'plumbing cylinder has a non-magnetic casing 40 

 mm. wide, 10 mm. thick and 750 mm. long and is in three 



Fig. 126. — Haussmana's apparatus assembled. 



parts; the lower one for taking the plumbing apparatus, 

 the middle one the registering apparatus and the upper 

 one the connection to the electric conductor. At the ends 

 of the middle section are two corresponding graduated 

 circles divided into 10-deg. intervals; the two other sections 

 carry reading marks. The upper mark lies in the plane 

 of symmetry of the suspension device and the lower one 

 corresponds with channels in the lower casing in which 



