On Electro- Dynamic Induction. 239 



distance was tolerably strongly magnetized, as was shown by the 

 quantity of filings which would adhere to it. The direction of 

 the current was still the same as that of the battery. The form 

 of the room did not permit the two wires to be separated to a 

 greater distance. The whole length of the circuit of the interior 

 large wire was about eighty feet ; that of the exterior one hun- 

 dred and twenty. The two were not in the same plane, and a 

 part of the outer passed through a small adjoining room. 



123. The results exhibited in this experiment are such as could 

 scarcely have been anticipated by our previous knowledge of the 

 electrical discharge. They evince a remarkable inductive en- 

 ergy, which has not before been distinctly recognized, but which 

 must perform an important part in the discharge of electricity 

 from the clouds. Some effects which have been observed during 

 thunder storms, appear to be due to an action of this kind. 



124. Since a discharge of ordinary electricity produces a sec- 

 ondary current in an adjoining wire, it should also produce an 

 analogous effect in its own wire ; and to this cause may be now 

 referred the peculiar action of a long conductor. It is well 

 known that the spark from a very long wire, although quite 

 short, is remarkably pungent. I was so fortunate as to witness a 

 very interesting exhibition of this action during some experi- 

 ments on atmospheric electricity made by a committee of the 

 Franklin Institute, in 1836. Two kites were attached, one 

 above the other, and raised with a small iron wire in place of a 

 string. On the occasion at which I was present, the wire was 

 extended by the kites to the length of about one mile. The 

 day was perfectly clear, yet the sparks from the wire had so 

 much projectile force, (to use a convenient expression of Dr. 

 Hare,) that fifteen persons, joining hands and standing on the 

 ground, received the shock at once, when the first person of the 

 series touched the wire. A Leyden jar being grasped in the hand 

 by the outer coating, and the knob presented to the wire, a severe 

 shock was received, as if by a perforation of the glass, but which 

 was found to be the result of the sudden and intense induction. 



125. These effects were evidently not due to the accumulated 

 intensity at the extremities of the wire, on the principles of ordi- 

 nary electrical distribution, since the knuckle required to be 

 brought within about a quarter of an inch before the spark could 

 be received. It was not alone the quantity, since the experi- 



