ELECTRIC LIGHTING.
150
It is surprising that with a current having so little tension such results could be obtained, and some sceptical persons would at first have denied the fact, contending that in order
to obtain a focus of electric light
equal to that of at least
30 Bunsen
an electro-motive force cells was required ; but
such persons did not observe that with incandescent lamps there
is
circuit,
no appreciable solution of continuity in the metallic and that a source of electricity of quantity suffices
If from the to produce incandescence in such a circuit. resistance of a light circuit, four or five thousand metres
of telegraph wire be taken away, together with the nearly equivalent resistance of the battery, and that of the electro-
magnetic apparatus of the regulator,
it
may be understood
how an
electro-motive force equal to that of only 4 Daniell cells can produce effects of incandescence in a circuit of
extremely small resistance, and even produce several points of by derivations from the current, since the total resistance
light,
of the circuit to
is
then in a manner diminished proportionably derivations. We are not sufficiently
number of
the
familiarized with effects of this kind,
made by confounding phenomena
and mistakes are often produced under
that are
very different electrical conditions.
Light produced by
A
means of an inductive
short time before his death, Fuller,
action*
who had been one
of Edison's fellow labourers, invented a system of electric on which we think it right to say a few words, although it appears to us scarcely practical. Here, however, lighting,
'
is
the description of it given in the Telegraphic Journal : In this system the principal current does not produce the
engenders another current in a series of induction is lighted by the current of one of the
light,
but
coils,
and each lamp
coils.
it
An alternating
current must be used.
The induction
were constructed as follows: Two magnetic cores, placed parallel to each other, were magnetically connected Round the centre of each of these cores was a at one end. coils