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 b, the shocks 
were very slight; 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, b 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 ata 
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 Tesulting effect is therefore only the difference of the tw0; 
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 eur 
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, W4 
increased to thirty six inches. ie 
_ 49. The action at a distance was still further increased by coll- 
ing the long wire of the large spool into the form of a ring of 
