50 



DISPLACEMENT INTERFEROMETRY BY 



dynamometer (<p) and at the vibrator (s), when different resistances R were 

 added to the circuit. Ri was practically the same both for .R=i,ooo and 

 2,000 ohms, to the degree in which i is measurable by the Siemens apparatus. 

 Moreover, the independent relation of HQ and 5 as seen in figure 53, is nearly 

 linear for W, B, G. The data are very much more satisfactory than I had 

 ventured to expect, except for the case of helix D. 



_JBO 



\ 



50 



40 



-tOO $00 300 



~5JO WO 700 800 

 Si ' 



ft) 40 60 80 100 



These coils were wound on non-conductors or split brass and of about the 

 same length. Coil D, however, was wound on a rather thick brass tube with- 

 out a longitudinal fissure. Hence it is probably the mutual induction which 

 accounts for the low value of s/l for this coil, which was about 1.8 times longer 

 than the others. 



To test these questions further I wound coils on glass tubes as follows, to 

 be compared with B already treated above : 



