206 
IOWA ACADEMY OF SCIENCE Vor,. XXVII, 1920 
0bscis$a =ThieHne%s 
of 
SPecii-ic 
ord,n»*e 
• 
bf Prse*’ ** ** * 
® Po.-«t-s Tmhs e 
Me-rntur^mentS 
t.«, Protest ^n. 
& 
% 
■ 
Fig. 40 
¥ 
modified as explained above (points marked 0). It will be seen 
that for those films obtained by the unmodified process, the 
resistance is not only much higher than that of the others, but 
the variations are much greater. 
