90 INDUCTION SHOCKS 
ferred to the smaller ones recommended by the Paris 
Congress. 
Assuming as the standard, then, an inductorium hav- 
ing coils about 13 cm. long and having in the secondary 
approximately 10,000 turns of wire, we may inquire 
how widely an inductorium can vary from this standard 
without introducing a significant error. For answering 
this question I have made observations with six in- 
ductoria, three of which are of "standard" construction 
and provided with Kronecker graduations, the other 
three selected to give increasing degrees of divergence 
from the standard. Details of the construction of the 
six inductoria are set down in Table VIII. 
The results of my numerous experiments with these 
inductoria may be summarized as follows: The three 
standard coils, A, B, and G, give corresponding values 
of Z for equal stimuli and equal secondary resistances 
whatever the secondary resistance may be. In compar- 
ing them, therefore, the factor of inductorium construc- 
tion does not enter. 
In thirteen experiments in which coil N was compared 
with coil B the secondary resistances ranged between 
2850 ohms and 25,000 ohms; the average percentage 
variation of Z N * from Z B was 6 per cent; the greatest 
variation was n.6 per cent. Z N was greater than Z B 
* For convenience of expression a subscript is placed after the value 
of Z to indicate with which coil the value was obtained. 
