PROTECTION FROM LIGHTNING. 



459 



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 con- 

 sideration in the form of a protector than solid section. In this 

 matter of the form of a conductor we follow Lodge, and prefer 



IMPULSIVE RUSH DISCHARGE, SO-CALLED DARK FLASHES. 



the tape to the solid rod. Increase of surface diminishes imped- 

 ance ; 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. 



