M. Bede, of Brussels, has an article in _L'Ingénieur-Conseil_ on the
above subject. He considers that a system of such wires forms the best
and most complete security against lightning with which a town can be
provided, because they protect not only the buildings in which they
terminate, but also those over which they pass. At each end they
communicate with the earth, and thus carry off safely any surplus
of electricity with which they may become charged. It is, however,
important that they should be provided with lightning conductors of
their own, to carry off such surplus directly from the transmission wire
to the earth wire, without allowing it to pass through the fine wires of
the induction coils, which it might fuse.
Such lightning conductors usually consist of a toothed plate attached to
one wire, close to another plate not toothed attached to the other wire.
The copper even of such a conductor has been melted by the powerful
current which it has carried away. In telephonic central offices, M.
Bede has seen all the signals of one row of telephone wires fall at the
same moment, proving that an electric discharge had fallen upon the
wires, and been by them conveyed to earth.
This fact shows that wires, even without points, are capable of
attracting the atmospheric electricity; but it must be remembered that
there are two points at every join in the wire. M. Bede insists strongly
upon the uselessness of terminating lightning conductors in wells,
or even larger pieces of water. The experiments of MM. Becquerel
and Pouillet proved that the resistance of water to the passage of
electricity is one thousand million times greater than that of iron;
consequently, if the current conveyed by a wire one square mm. thick
were to be carried off by water without increased resistance, a surface
of contact between the wire and the water of not less than 1,000 square
meters must be established.
It is obvious that a wire let down into a well is simply useless. On
the two-fluid theory, it offers no effectual way of escape to the
terrestrial electricity; according to the older views, it would be
absolutely dangerous, by attracting more electricity from the clouds
than it could dispose of. The author advocates connecting lightning
conductors with water or gas pipes, which have an immense surface of
contact with the earth.
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