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IOWA ACADEMY OF SCIENCE Vol. XXIV, 1917 
time and the temperature variation was relatively small. An- 
other factor that varied, at least between the first and second 
sets, was the initial p.g., at which the conduction current began. 
Still another possible factor was a progressive drying effect due 
Figure 38 
to the slow stream of dried air that was being continually passed 
through the apparatus, although the effect of drying on the 
minimum insulating distance appeared to have ceased before 
the first set of readings of current was taken. 
