142 WRITINGS OP JOSEPH HENRY. [1838 



at the places so cut. Pass a discharge through the tinfoil 

 from about nine half gallon jars; the ends, at each separa- 

 tion, will be thrown up, and sometimes bent entirely back, 

 as if by the action of a strong repulsive force between them. 



This will be understood by a ref- 



^ y erence to Fig. 14; the ends are 



^K=^^%E=:>^^^^^==' shown bent back at a, a, a, a. In 

 Fig 14.-6 glass plate; a, a, a, a, the popular experiment of the 

 openings in tinfoil. pierccd Card, the bur on each side 



appears to be due to an action of the same kind. 



127. It now appears probable, from the facts given in para- 

 graphs 119 and 120, that the table in paragraph 92 is only 

 an approximation to the truth, and that each current from 

 galvanism, as well as from electricity, first produces an in- 

 ductive action in the direction of itself, and that the inverse 

 influence takes place at a little distance from the wire. 



128. -To test this the compound helix was placed on coil 

 No. 1, to receive the induction, and its ends joined to those 

 of the outer ribbon of tinfoil of the glass cylinder, while the 

 magnetizing spiral was attached to the ends of the inner 

 riband. A feeble tertiary current was produced by this 

 arrangement, which in two cases gave a polarity to the 

 needle indicating a direction the same as that of the primary 

 current. In other cases the magnetism was either imper- 

 ceptible or minus. With an arrangement of two coils of 

 wires around two glass cylinders, one within the other, the 

 same effect was produced. The magnetism was less when 

 the distance of the two sets of spires was smaller, indicating, 

 as it would appear, an approximation to a position of neu- 

 trality. These results are rather of a negative kind, yet they 

 appear to indicate the same change with distance in the case 

 of the galvanic currents as in that of the discharge of ordi- 

 nary electricity. The distance however at which the change 

 takes place would seem to be less in the former than in the 

 latter. 



129. There is a perfect analogy between the inductive 

 action of the primary current from the galvanic apparatus 

 and of that from the larger electrical battery. The point 

 of change, in each, appears to be at a great distance. 



