to Electricity and Magnetism. 255 



cumference, at 6, the shocks were very slight; and when 

 placed within, but its axis at right angles to that of the ring, 

 not the least eiFect could be observed. 



47- With a little reflection, it will be evident that this ar- 

 rangement is not the most favourable for exhibiting; the in- 

 duction at a distance, since the side of the ring, for example, 

 at c, tends to produce a current revolving in one direction 

 in the near side of the helix, and another in an opposite di- 

 rection in the further side. The resulting effect is therefore 

 only the difference of the two, and in the position as shown 

 in the figure ; this difference must be very small, since the 

 opposite sides of the helix are approximately at the same di- 

 stance from c. But the difference of action on the two sides 

 constantly increases as the helix is brought near the side 

 of the ring, and becomes a maximum when the two are in 

 the position of internal contact. A helix of larger diameter 

 would therefore produce a greater effect. 



48. Coil No. 1 remaining as before, helix No. 1, which is 

 nine inches in diameter, was substituted for the small helix of 

 the last experiment, and with this the effect at a distance was 

 much increased. When coil No. 2 was added to coil No. 1, 

 and the currents from two small batteries sent through these, 

 shocks were distinctly perceptible through the tongue, when 

 the distance of the planes of the coils and the three helices, 

 united as one, was increased to thirty-six inches. 



49. The action at a distance was still further increased by 

 coiling the long wire of the large spool into the form of a 

 ring of four feet in diameter, and placing parallel to this an- 

 other ring, formed of the four ribands of coils No. 1, 2, 3 and 

 4. When a current from a single battery of thirty-five feet 

 of zinc surface was passed through the riband conductor, 

 shocks through the tongue were felt when the rings were se- 

 parated to the distance of four feet. As the conductors were 

 approximated, the shocks became more and more severe ; 

 and when at the distance of twelve inches, they could not be 

 taken through the body. 



50. It may be stated in this connexion, that the galvanic 

 induction of magnetism in soft iron, in reference to distance, 

 is also surprisingly great. A cylinder of soft iron, two inches 

 in diameter and one foot long, placed in the centre of the ring 

 of copper riband, v.ith the battery above mentioned, be- 

 comes strongly magnetic. 



51. I may perhaps be excused for mentioning in this com- 

 munication that the induction at a distance affords the means 

 of exhibiting some of the most astonishing experiments, in the 

 line of physique amusante, to be found perhaps in the whole 



