The wire used in making helices for the magnets, and for connecting
the telegraphic stations, is made of copper of the best quality, and
annealed. It is covered with cotton thread, so as to conceal every part
of the metallic surface, not so much to prevent corrosion or waste
from the action of the atmosphere, as to prevent a metallic contact of
one wire with another, when placed near each other. After the wire is
covered, it is then saturated with shellac, and then, again, with a
composition of asphaltum, beeswax, resin and linseed oil. It is now in
a condition to be extended upon the poles. That portion of the wire of
which the helices are made is only saturated with shellac.