standing out at
right angles with the rod. Indeed, some go even beyond this, forming
points along the whole length of the conductors by notching the corners
of a square rod with a chisel. Sometimes a rod is twisted for ornament,
but with a loss for practical uses, for in a twisted rod the electrical
current is retarded, and a portion of the charge is more liable to leave
the conductor.

In England, during our Revolutionary war, an active scientific
discussion was carried on as to whether the upper end of a
lightning-conductor should be sharp or blunt. "The scientific aspect of
the question soon became lost in political acrimony, those who, with Dr.
Franklin, advocated sharp conductors, being classed with him and the
Revolutionary party, while those who advocated blunt conductors were
held to be loyal subjects and good citizens." There is a difference in
the action of a sharp conductor and one with a blunt end or terminating
in a ball. In the first the point silently receives the current, while
in the other the opposite electricities of the rod and cloud may meet
with explosion; but the building will not necessarily be injured from
this cause. M. Michel proposed to combine the advantages of the two
systems by having the rod terminate in a spherical enlargement from
which should project points in various directions. This, he thought,
would lessen the danger of fusion and control the current at distances
where it might escape other forms of terminal. Some American
electricians now use a modification of this form, surmounting the rod
with a branching tip, while others prefer the single point. The latter
is the form used in the American and British navies. The vane, with its
appurtenances, is sometimes made the terminal of the conductor, and
should at least always be connected.

The practice is also a good one of combining balustrades, finials and
other metal-work at the tops of buildings with the system, by which
protection is rendered more complete. Especially is it important to
connect with a metallic roof at its lower edge, and with the gutters,
unless the rain-conductors connect with the earth to its moist mass.

In regard to the material for conductors, copper is undoubtedly the
best, but more expensive than iron. The latter is more liable to rust,
and on account of its lower conductive power is more easily melted. An
electrical explosion which only melts a copper wire would utterly
destroy an iron wire of twice th