220 Contributions to Electricity and Magnetism. 



inner circumference, as at c ; but when it was placed without the 

 ring, in contact with the outer circumference, at 6, the shocks 

 were very shght ,• and when placed within, but its axis at right 

 angles to that of the ring, not the least effect could be observed. 



Fig. 4. 



a helix No. 4, h coil No. 1, in the form of a ring. 



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

 ment is not the most favorable for exhibiting the induction 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 direction in the farther side. 

 The resulting eflect 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 distance 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 in- 

 creased. When coil No. 2 was added to coil No. 1, and the cur- 

 rents 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 coil- 

 ing the long wire of the large spool into the form of a ring of 



