554; Prof. J. Henry's Contributions 



108. Experiments were next made in reference to the pro- 

 duction of currents of the different orders by ordinary elec- 

 tricity. For this purpose a second cylinder was prepared 

 with ribands of tinfoil, in a similar manner to the one before 

 described. The two were then so connected that the secondary 

 current from the first would circulate around the second. 

 When a discharge was passed through the outer riband of 

 the first cylinder, a tertiary current was induced in the inner 

 riband of the second. This was rendered manifest by the 

 magnetizing of a needle in a spiral joining the ends of the 

 last-mentioned riband. 



109. Also by the addition, in the same way, of a third cy- 

 linder, a current of the fourth order was developed. The 

 same result was likewise obtained by using the arrangement 

 of the coils and helices shown in fig. 9. For these experi- 

 ments, however, the coils were furnished with a double coat- 

 ing of silk, and the contiguous conductors separated by a 

 large plate of glass. 



110. Screening effects precisely the same as those exhibited 

 in the action of galvanism were produced by interposing a 

 plate of metal between the conductors of different orders, 

 figures 8 and 9. The precaution was taken to place the plate 

 between two frames of glass, in order to be assured that the 

 effect was not due to a want of perfect insulation. 



111. Also analogous results were found when the experi- 

 ments were made with coils interposed instead of plates, as 

 described in paragraph 68. When the ends of the inter- 

 posed coils were separated, no screening was observed ; but 

 when joined, the effect was produced. The existence of the 

 induced current, in all these experiments, was determined by 

 the magnetism of a needle in a spiral attached to one of the 

 coils. 



112. Likewise shocks were obtained from the secondary 

 current by an arrangement shown in fig. 12. Helices No. 2 

 and No. 3 united are put within a glass jar, and coil No. 2 is 

 placed around the same. When the handles are grasped, a 

 shock is felt at the moment of the discharge, through the outer 

 coil. The shocks, however, were very different in intensity 

 with different discharges from the jar. In some cases no 

 shock was received, when again, with a less charge, a severe 

 one was obtained. But these irregularities find an explana- 

 tion in a subsequent part of the investigation. 



113. In all these experiments, the results with ordinary 

 and galvanic electricity are similar. But at this stage of the 

 investigation there appeared what at first was considered a 

 remarkable difference in the action of the two. I allude to 



