On Electro- Dynamic Induction. 235 



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 experiments 

 were made with coils interposed instead of plates, as described in 

 paragraph 68, When the ends of the interposed coils were sep- 

 arated, 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. 



Fig. 12. 



a coil No. 2, h an inverted bell glass, c helices No. 2 and 3. 



112. Likewise shocks were obtained from the secondary cur- 

 rent 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 explanation 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 investi- 

 gation there appeared what at first was considered a remarkable 

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

 the currents of the different orders. These, in the experiments 

 with the glass cylinders, instead of exhibiting the alternations of 

 the galvanic currents (92,) were all in the same direction as the 

 discharge from the jar, or, in other words, they were all plus. 



114. To discover, if possible, the cause of this difference, a 

 series of experiments was instituted ; but the first fact developed. 



