Page:Handbook of Meteorology.djvu/124

 Thunder-storms.—The phenomena of thunder-storms have been known ever since human beings peopled the earth. The cause or causes are still imperfectly known.

Thunder-storms derive their name from the reverberations and crashes of thunder following lightning discharges, which possess an intensity unknown except in nature. These discharges take place between cloud and earth, between earth and cloud, and between cloud and cloud. But the lightning discharges are not the cause of the storm; they are incidents merely in its progress; and except in intensity and volume the thunder does not differ from the snapping of an electric spark.

Several things take place in the formation of a

After Humphreys.

Experiments have shown that a blast of air driven against drops of distilled water, with a force sufficient to blow them into spray, produces both positive and negative