104 INDUCTION SHOCKS 
was wholly inexplicable until the development of the 
make shock formula made its meaning clear. 
Although the make shock formula 
presents the appearance of some complexity, as a matter 
of fact it is a comparatively easy task to derive the value 
of C, which is the only new constant the equation re- 
quires, and with the constant once established the use 
of the formula is perfectly simple. To determine how 
laborious is the task of determining the value of C, an 
inductorium was taken which had been previously cali- 
brated for break shocks, and seven experiments were 
found to yield sufficient data to establish conclusively 
the value of the constant. 
The experimental procedure is that described on p. 95. 
The interpretation of the results so as to establish 
the constant depends upon recognition of the fact that 
in such experiments as these the value of Z m for the inner 
positions of the secondary coil, where threshold stimu- 
lation is obtained with very small primary currents, is 
practically independent of the value of the constant; 
whereas the value of Z m for secondary positions far out 
on the scale, where heavy primary currents must be 
