Figs. 17 & 18.—SHOWING THE EFFECT OF THE UNION AND THE SEPARATION OF THE CHARCOAL POINTS.
580. What is the cause of lightning?
Lightning is the result of electrical discharges from the clouds.
581. What develops electricity in the clouds?
Evaporations from the surface of the earth; changes of temperature in the atmospheric vapour; chemical action upon the earth's surface; and the friction of volumes of air of different densities against each other.
"His lightnings enlightened the world: the earth saw and trembled."—Psalm xcvii.