ELECTRICAL MEASUREMENTS 



335 



where D is the deflection. When D is equal to zero 



\-r'} A = o 



or 



In the experiments by this method the microfarad Elliott condenser 

 was used, and it was compared with the different coils P 1} P z , A, and C. 

 The connections were made with open leads and open resistances were 

 used as far as possible, but it was necessary to use resistance boxes for 

 the last adjustments. The connections having been made as in figure, 

 the process of experimenting was to keep r and / constant and to 

 adjust R" and R until there was no deflection of the hanging coil. The 

 resistance of the circuits R" -\- r' and R -\- r were then measured on a 

 Wheatstone bridge. The commutator A' was reversed and the process 

 was repeated. The condenser had absorption (see p. 323) which caused 

 the resistance R" -f- r' to be increased by 7-11 ohms. When the capac- 

 ity is calculated, taking into account the absorption, it is called the 

 corrected capacity, as in the other tables of the paper. 



COLLECTED RESULTS. 



n=133. 



Results found by taking sum 



and diff . of separate 



measurements. 



5648 (C + Y l )C=P l 



5730 (C + PI + P a ) (C + P a )=P, 



7187 (C + P a ) C=P 2 



7269 (C + P. + P,) (C + P,) = P, 



3029 (C + P,) P, = C 



2990 (C + P S ) P 4 =C 



3065 (C + P, + P a ) P, P 2 =C 



3022 (A + C) C=A 



2917 (C + P, + P 2 ) C=P, + P a 



2888 P, + P a 



8677 C + P, 



8718 (C + Pj + P.,) P a =C + P 1 



0298 (C + P, + P a ) P,=C + P a 



5920 P! + P a + C 



6025 A + C=A + C 



In method 12 corrections due to the hanging coil and fixed coils were 

 calculated so that the ratio of the resistances would give the ratio of the 

 self-inductances direct. In this method (6) since the capacity was in 

 circuit with the hanging coil, the self-inductance was so small that it 

 was neglected. The self-inductance of the coils P, etc., which were 

 joined in circuit with the fixed coils, were increased by the self-induc- 

 tance of the fixed coils, that is by -0164 henry. 



