16 INDUCTION SHOCKS 
Kronecker,* in 1871, introduced a modification of the 
method whereby its application was simplified. He used 
two inductoria, connected their secondary coils in series 
with a galvanometer and connected both primary coils 
with a single source of current in such fashion that the 
two secondaries gave induced currents opposite in direc- 
tion when the primary circuit was broken. Thus the 
galvanometer deflection was used merely as an indicator 
that one induced current was stronger than the other, 
rather than as a measure of the strength of the induced 
current itself. 
With both secondaries at zero the primary current 
was broken and the amount and direction of deflection 
noted. The coil giving a stronger shock was then moved 
outward till no deflection occurred. Then the weaker 
coil was moved outward till a deflection equal to the 
first one was obtained. This procedure was repeated 
till the whole length of the slide had been traversed, the 
number of times the stronger secondary was moved be- 
ing noted. If this number is multiplied by the original 
galvanometer deflection we have a value which ex- 
presses how many times greater the galvanometer de- 
flection would be with the secondary at zero than at the 
end of the slide. To calibrate the slide on the basis of 
1000 units, as Kronecker does, the total deflection noted 
* Kronecker: Arbeiten aus der physiologischen Anstalt zu Leipzig, 
1871, S. 186. 
