558 Prof. J. Henry's Contributions 



indicated a current in the same direction as that of the battery. 

 When the distance of the two wires was increased to sixteen 

 inches, and the ends of the second wire placed in two glasses 

 of mercury and a finger of each hand plunged into the metal, a 

 shock was received. The direction of the current was still the 

 same, but the magnetism not as strong as at a less distance. 



122. The second wire was next arranged around the other, 

 so as to inclose it. The magnetism by this arrangement ap- 

 peared stronger than with the last ; the direction of the cur- 

 rent was still the same, and continued thus, until the two wires 

 were at every point separated to the distance of twelve feet, ex- 

 cept in one place where they were obliged to be crossed at the 

 distance of seven feet, but here the wires were made to form a 

 right angle with each other, and the effect of the approxi- 

 mation 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 was 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 know- 

 ledge of the electrical discharge. They evince a remarkable 

 inductive energy, which has not before been distinctly recog- 

 nised, but which must perform an important part in the dis- 

 charge 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 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 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 con- 



