ON ELECTRO-DYNAMIC INDUCTION. 333 



made to form a right angle with each other, and the effect of the ap- 

 proximation was therefore (46) considered as nothing. The needle at 

 this surprising 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 w^as about 

 eighty feet; that of the exterior one hundred 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 elec- 

 trical discharge. They evince a remarkable inductive energy, 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 secondary 

 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 knowm 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 experiments on atmospheric electricity made by a com- 

 mittee 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 w-hich was found to be the result of the sudden and intense 

 induction. 



