The electric strength of air — VI

(1) Some of the simpler fundamental experiments on the electrical conductivity of the air are described. (2) The theory of ionization in gases is outlined in nontechnical language. (3) Townsend's proof that the law of corona forming intensity
$E=32+{13.4 \over {\sqrt d}}$
is in accord with the theory of ionization by collision, is explained.