CHAPTER III 
A SUMMARY OF PROCEDURE 
FOR the convenience of users of the method herein 
presented it has been thought worth while to describe 
briefly at the outset the various pieces of apparatus 
used and to summarize the various procedures involved 
in making the necessary calibrations and in using the 
calibrated apparatus. 
Instruments Required for the Calibration. The in- 
ductorium to be calibrated should be of " standard " 
construction (see p. 88), that is, it should have a sec- 
ondary coil approximately 13 cm. long and having about 
10,000 turns of wire. The number of turns and the 
mean cross section of the secondary coil must be accu- 
rately known (p. 55). The slide upon which the sec- 
ondary moves should be not less than 30 cm. long. It 
should be accurately graduated in millimeters, and a 
pointer fixed to the secondary coil in such position as to 
stand at zero when the secondary is pushed completely 
over the primary. To increase the stimulating effec- 
tiveness of the instrument the primary coil should have 
a core made of a bundle of soft iron wires. 
In addition to this inductorium there is needed a con- 
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