On Electro-Dynamic Induction. 121 
at beginning was slightly increased ; with three elements the in- 
crease was more decided, while the shock at breaking the circuit 
remained nearly of the same intensity as at first, or was compar- 
atively but little increased. When the number of elements was 
increased to ¢en, the shock at making contact was found fully equal 
to that at breaking, and by employing a still greater number, the 
former was decidedly stronger than the latter, the difference con- 
tinually increasing until all the thirty elements were introduced 
into the circuit. 
9. In my last paper, a few experiments are mentioned as being 
made with a compound battery of Cruickshank’s construction ; 
but from the smallness of the plates of this, and the rapidity with 
which its power declined, I was led into the error of supposing 
that the induction at the ending of the current, in the case of a 
short coil, was diminished by increasing the intensity of the bat- 
tery, (see paragraph 19, of No. ILI,) but by employing the more 
perfect instrument of Professor Daniell in the arrangement of the 
last experiment, I am enabled to correct this error, and to state 
that the induction at the ending remains nearly the same, when 
the intensity of the battery is increased. If the induction de- 
pends in any degree on the quantity of current electricity in the 
conductor, then a slight increase in the induction should take 
place, since, according to theory, the current is somewhat in- 
creased in quantity, in the case of a long coil, by the increase of 
the intensity of the battery. Although very little, if any, diffe- 
rence could be observed in the intensity of the shock from the 
secondary current, yet the snap and deflagration of the mercury 
appeared to be greater from the primary current, when éen ele- 
ments of the battery were included in the circuit, than with a 
single one. The other results which are mentioned in my last 
Paper in reference to the compound battery are, I believ €, cor- 
rectly given. eee). 
10. The intensity of the different shocks in the foregoing ex- 
periments was compared by gradually raising the helix from the 
coil, (see Fig. 3,) until, on account of the distance of the con- 
ductors, the shock in one case would be so much reduced as to 
be scarcely perceptible through the fingers or the tongue, while 
the shock from another arrangement, but with the same distance 
of the conductors, would be evident, perhaps, in the hands. The 
same method was generally employed in the experiments in which 
Vol. xx1, No. 1.—April-June, 1841. 16 
