561 
to Electricity and Magnetism, 
figure, falls in the jplus region of the primary current, and in 
the minus region of the secondary, and hence the two actions 
neutralize each other, and no apparent result is produced. 
] 32. Fig. 16 indicates the method in which the neutralizing 
effect is produced in the case 
of the secondary and tertiary Fig. 1 6. 
currents. The wire con- + ^ 
ducting the secondary cur- ± 
rent is represented by b, ~~ - T ^ 
that conducting the tertiary -- + ^ 
by c, and the other wire, to ^ — + 
receive the induction from I ij: 
these, by d. The direction 
of the influence, as before? is indicated by + 0 , &c., 
and the third wire is again seen to be in the plus region of 
the one current, and in the minus of the other. If, however, 
d is placed sufficiently near c, then neutralization will not 
take place, but the two currents will conspire to produce in 
it an induction in the same direction. A similar effect would 
also be produced, were the wire c, in fig. 15, placed sufficiently 
near the conductor h, 
133. Currents of the several orders were likewise produced 
from the excitation of the magneto-electrical machine. The 
same neutralizing effects were observed between these as in 
the case of the currents from the galvanic battery, and hence 
we may infer that also the same alternations take place in the 
direction of the several currents. 
134*. In conclusion, I may perhaps be allowed to state, 
that the facts here presented have been deduced from a la- 
borious series of experiments, and are considered as form- 
ing some addition to our knowledge of electricity, independ- 
ently of any theoretical considerations. They appear to be 
intimately connected with various phaenomena, which have 
been known for some years, but which have not been referred 
to any general law of action. Of this class are the discoveries 
of Savary, on the alternate magnetism of steel needles, placed 
at different distances from the line of a discharge of ordinary 
electricity*, and also the magnetic, screening influence of all 
metals, discovered by Dr. Snow' Harris of Plymouth f. A 
comparative study of the phaenomena observed by these di- 
stinguished savants^ and those given in this paper, would 
probably lead to some new and important developments. In- 
deed every part of the subject of electro-dynamic induction 
* Annates de Chimie et de Physique ^ 1827. 
f Philosophical Transactions, 1831, [noticed in Phil. Mag. and Annals, 
N. S. Vol. X. p. 297-298.] 
