Page:Popular Science Monthly Volume 43.djvu/475

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459
PROTECTION FROM LIGHTNING.

ing rapidly in direction—the interior of the conductor may carry far less than the surface carries.

All of which goes to prove the correctness of Snow Harris's opinion (and he probably studied the effects of lightning more exhaustively than any one else) that surface was more of a consideration in the form of a protector than solid section. In this matter of the form of a conductor we follow Lodge, and prefer

PSM V43 D475 Impulsive rush discharge known as dark flashes.jpg
Impulsive Rush Discharge, So-called Dark Flashes.

the tape to the solid rod. Increase of surface diminishes impedance; and as impedance is probably at the bottom of side flashes and spittings, that conductor is to be prefered which offers less impedance, and hence tape appears to be preferable to rod. It is also more convenient, and it has also the advantage of being made either continuous or in very long lengths. The tape must be of dimensions sufficient to withstand melting or deflagration.