552 



Prof. J. Henry's Contributions 



of considerable energy, gave some indication that similar 

 effects might be produced by a discharge of ordinary elec- 

 tricity, provided a sufficiently perfect insulation could be ob- 

 tained. 



100. To test this, a hollow glass cylinder, fig. 11, of about 

 six inches in diameter, was prepared with a narrow riband of 



Fig. 11. 



a glass cylinder, b Leyden jar, c magnetizing spiral. 



tinfoil, about thirty feet long, pasted spirally around the out- 

 side, and a similar riband of the same length, pasted on the 

 inside ; so that the corresponding spires of the two were di- 

 rectly opposite each other. The ends of the inner spiral 

 passed out of the cylinder through a glass tube, to prevent 

 all direct communication between the two. When the ends 

 of the inner riband were joined by the magnetizing spiral 

 (11.), containing a needle, and a discharge from a half-gallon 

 jar sent through the outer riband, the needle was strongly 

 magnetized in such a manner as to indicate a7i induced current 

 through the inner riband in the same direction as that of the 

 current of the jar. This experiment was repeated many times, 

 and always with the same result. 



101. When the ends of one of the ribands were placed 

 very nearly in contact, a small spark was perceived at the 

 opening, the moment the discharge took place through the 

 other riband. 



102. When the ends of the same riband were separated 

 to a considerable distance, a larger spark than the last could 

 be drawn from each end by presenting a ball, or the knuckle. 



103. Also if the ends of the outer riband were united, so 

 as to form a perfect metallic circuit, a spark could be drawn 

 from any point of the same, when a discharge was sent 

 through the inner riband. 



lO-i. The sparks in the two last experiments are evidently 

 due to the action known in ordinary electricity by the name 

 of the lateral discharge. To render this clear, it is perhaps 



