Chapter III. applies this theory to thunder clouds, which are formed by

the rapid inter-mixture of masses of the atmosphere thrown into circulation by heat. There are some capital descriptions of thunder clouds. They are often accompanied by whirlwinds, and always by rain. It is the friction of the whirlwind on the drops of rain that developes electricity—the rain being positively, and the air negatively, electrified. Hail is due to the ascending current of air carrying the drops of water to the region of snow and frost! His notions are somewhat hazy, thus:—“Much of the positive electricity is conveyed to the earth by the lightning; but the corresponding negative electricity from being carried upwards with the vertical wind, cannot so easily escape to the earth, so that the storm cloud contains, on the whole, more negative electricity than positive electricity” (p. 38.)