218 Contributions to Electricity and Magnetism. 
coil, of great quantity and feeble intensity ; but succeeding ex- 
periments wil] show that this is not necessarily the case. 
38. All the experiments given in this section have thus far been 
made with a battery of a single element. This condition was 
now changed, and a Cruickshank trough of sixty pairs substitu- 
ted. When the current from this was passed through the riband 
coil No. 1, no indication, or a very feeble one, was given of a 
secondary current in any of the coils or helices, arranged as in 
the preceding experiments. The length of the coil, in this case, 
was not commensurate with the intensity of the current from the 
battery. But when the long helix, No. 1, was placed instead of 
coil No. 1, a powerful inductive action was produced on each of 
the articles, as before. 
39. First, helices No. 2 and 3 were united into one, and placed 
within helix No. 1, which still conducted the battery current. 
With this disposition a secondary current was produced, which 
gave intense shocks but feeble decomposition, and no magnetism 
in the soft iron horse-shoe. It was therefore one of intensity, and 
was induced by a battery current also of intensity. 
40. Instead of the helix used in the last experiment for receiv- 
ing the induction, one of the coils (No. 3) was now placed on he- 
lix No. 1, the battery remaining as before. With this arrange- 
ment the induced current gave no shocks, but it magnetized the 
small horse-shoe; and when the ends of the coil were rubbed 
together, produced bright sparks. It had therefore the properties 
gf a current of quantity; and it was produced by the induction 
of a current, from the battery, of intensity. ‘ 
41. This experiment was considered of so much im ’ 
that it was varied and repeated many times, but always with the 
same result; it therefore establishes the fact that an intensity 
current can induce one of quanity, and, by the preceding experi- 
ments, the converse has also been shown, that a quantily current 
can induce one of intensity. 
42. This fact appears to have an important bearing on the law 
of the inductive action, and would seem to favor the supposition 
that the lower coil, in the two experiments with the long a0 
short secondary conductors, exerted the same amount of induc 
tive force, and that in one case this was expended (to use the lan- 
guage of theory) in giving a great velocity to a small quantity of 
the fluid, and in the other in producing a slower motion in a larget 
