Bare Wire for Resistance-coils. 219 



rature of the room, which led to some uncertainty as to the 

 actual temperature. 



The 1000 ohm standard coil was obtained by forming a 

 bridge with the 1, 10, 100, and 1000 ohm coils, and had a 

 value, on April 28, of 1000'24 ohms at 12 a 8. No other 

 determination has, as yet, been made. The coils were 

 adjusted so as to be right at 15°. 



V. Calibration of the Resistance-box. 



For the first three of the dials the coils were balanced 

 against standard coils (fig. 2), and the differences obtained 



Fig. 2. 



0*1 Ohm 



STANDARD 



WIRE BR! DGE. 



by means of the wire bridge. In order to connect the 

 conical plugs to the arms of the wire bridge, the flexible leads 

 with conical ends were used ; the standard in the opposite 

 arm being connected by means of the leads with mercury- 

 cup ends. 



For the 1 and 100 ohms in the proportional arms spade- 

 ended leads were used, and attached to the terminals at the 

 ends of the proportional arms (see diagram). 



For the sake of convenience of comparison, I have reduced 

 the resistances to their values at 11° C. 



The values of the -^ ohm dial are as follows : — 



