141 



PROCEDURE IN BALANCING BRIDGE 



Tlie bridge is balanced as follows : 



1. Adjustment of the setting of the slide wire so as to bring the sound 



in the telephone receivers to a small or minimum value. 



2. Without changing the setting of the slide wire, adjust the mutual 



inductance so as to further reduce the sound in the telephone re- 

 ceivers, if possible. 



3. Without changing either the setting of the slide wire or the mutual 



inductance, and with the ground switch closed, adjust the slider on 

 the third branch of the bridge so as to reduce the sound in the 

 telephone receivers as far as possible, being sure that connection 

 from the third branch to the shield is functioning properly. The 

 ground switcli should be kept open at all times except during this 

 adjustment. 



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4. Again adjust the setting of the slide wii-e so as to reduce the sound 



in the telephones, this time as far as possible or until the setting 

 of the slide wire is as definite as is desired. 



5. If the adjustment 4 can not be made as precisely as desired, all the 



adjustments should be repeated liefore recording the reading of the 

 setting of the slide wire. 



PROCKDURE IN" MAKING MEASUREMENTS 



The procedure to be followed in carrying out a measurement is as follows: 



1. Put into the auxiliary or Y cell sea water having a salinity slightly in 



excess of that which corresponds to a reading of 500 on the slide 



wire as given by the table or curve. This solution may be left in 



the cell more or less indefinit<^ly if the cell is kept properly closed. 



