STRENGTHS OF FARADIC STIMULI 15 
plex mechanism for varying and at the same time 
measuring the primary current. 
The earliest method of measuring induction shocks 
which received wide recognition was worked out under 
the direction of Fick by his student, Meyer, in 1869.* 
This method concerned itself altogether with the effect 
upon the intensity of break shocks of shifting the posi- 
tion of the secondary coil relative to the primary, and 
amounts, therefore, to a calibration of the slide upon 
which the secondary coil moves. By such calibration 
the relative intensities of the shocks given by the in- 
ductorium at the various secondary positions are accu- 
rately indicated, so long as all the other variable factors 
remain unchanged. A similar calibration is an essential 
feature of any scheme for the quantitative use of the 
inductorium, and indeed the only criticism of the Fick 
method of measuring stimuli is for its incompleteness. 
The Fick calibration was accomplished by including in 
the secondary circuit a galvanometer and determining 
the current induced in the secondary coil at its various 
positions by the deflection produced when a given cur- 
rent was made or broken through the primary. This 
method, although simple in theory, was in fact rather 
difficult to put into practice with the electrical measuring 
apparatus available in Fick's time; and accordingly 
* Meyer: Unters. phys. Labor, d. Zuricher Hochschule, Wien, 1869, 
8.36. 
