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MESSRS. G. F. C. SEAELE AXD T. G. EEDFOED 
maximum value. It would be necessary to make the core smaller than in the coil 
used hy us, so that in spite of the smaller section of the wire the resistance might 
still he small. 
Arrangement of the Apj^aratus. 
§ 35. After this description of the apparatus we proceed to explain, by the help of 
fig. G, how it was arranged. The battery SC, consisting of one or more small storage 
cells, was connected through the adjustable resistance and the Weston ampere¬ 
meter WA to the special reversing key Kj. An adjustable length of German-silver 
wire included in the circuit enabled us to keep the ciu’rent to a definite value for any 
length of time. On leaving the key K^, tlie current passes round the fixed coils of 
the electro-dynamometer ED, round the magnetising solenoid IMS and the choking 
coil CC, and finally round a compensating coil F. By adjusting the position of F, 
the small effect upon the ballistic galvanometer of the current passing through ED 
and MS was completely annulled. 
The circuit of the ballistic galvanometer BG contains a resistance box and the 
earth-inductor El, as well as the secondary coil U and the key Kn. 
The circuit of the suspended coil contains the resistance box Eg, the secondarv 
coil V, the key Kg, and the resistance coil X formed of copper wire adjusted to have 
the same resistance as the earth-inductor FIT, as described in § 23. 
To bring the susj)ended coil to rest a current of the order of 1/200,000 ampere was 
sent through the suspended coil l)y depressing the tapping key K^, a Leclanche 
cell L providing the current. In the actual experiments a system of shunts was 
used instead of the single high resistance which, for the sake of simplicity, is 
represented iu the diagram ; the effect is, however, the same in both cases. When 
