236 Contributions to Electricity and Magnetism. 
instead of affording any new light, seemed to render the obscu- 
rity more profound. When the directions of the currents were 
taken in the arrangement of the coils, (Fig. 9,) the discrepancy 
vanished. Alternations were found the same as in the case of 
galvanism. 'This result was so extraordinary that the experi- 
ments were many times repeated, first with the glass cylinders, 
and then with the coils; the results, however, were always t 
same. ‘The cylinders gave currents all in one direction; the coils 
in alternate directions. 
115. After various hypotheses had been formed, and in succes- 
sion disproved by experiment, the idea occurred to me that the 
direction of the currents might depend on the distance of the 
conductors, and this appeared to be the only difference existing 
in the arrangement of the experiments with the coils and the 
cylinders.* In the former the distance between the ribands was 
nearly one inch and a half, while in the latter it was only the 
thickness of the glass, or about ;\,th of an inch. — 
116. In order to put this supposition to the test of experiment, 
two narrow slips of tinfoil, about twelve feet long, were stretched 
parallel to each other, and separated by thin plates of mica to the 
distance of about ;;th of an inch. When a discharge from the 
half gallon jar was passed through one of these, an induced cul- 
rent in the same direction was obtained from the other. The 
ribands were then separated, by plates of glass, to the distance of 
asth of an inch; the current was still in the same direction, oF 
plus. When the distance was increased to about 1th of an inch, 
no induced current could be obtained; and when they were still 
further separated the current again appeared, but was noW found 
to have a different direction, or to be minus. No other change 
was observed in the direction of the current with a farther im 
crease of distance ; the intensity of the induction gradually dimip- 
ished as the ribands were separated. The existence and direction 
of the current, in this experiment, were determined by the polat- 
ity of the needle in the spiral attached to the ends of one of the 
ribands. 
117. The question at this time arose, whether the direction of 
the current, as indicated by the polarity of the needle, was the 
fo 5 al a Sees li <oN itttiol 
8 This idea Was not immediately adopted, because I had previously experimented 
on the direction of the secondary current from galvanism, and found no change = 
