According to ancient mythology, Prometheus, the brother of Atlas, was especially distinguished from other men by reason of his cunning. It seems, however, that he had provoked the anger of Jupiter by ridiculing the gods. To punish both him and the people on the earth, Jupiter took away the sacred fire from the earth; but Prometheus, aided by Minerva, climbed to the heavens and stole the fire from the chariot of the sun. Jupiter punished Prometheus for this impious act by chaining him to a rock on Mt. Caucausus, where he was condemned for 30,000 years to have a vulture feed on his liver, which, although constantly devoured, was continually miraculously renewed, thus per mitting the pain to continue for this great length of time.

Whether or not Prometheus actually did so draw down the lightning from the sky, we cannot of course say. He was a bright man, however, and may have got so far ahead of the rest of the world as to have actually made this discovery.

But Prometheus is not the only one who is thus credited with an early electrical knowledge. It is said that the Roman, Numa Pompilius, succeeded on several occasions in safely drawing down the sacred fire from the sky, but that another Roman who came after Pompilius, Tullus Hostilius, having found some notes that had been left by Numa on the sacred art of worshipping Jupiter, had been struck dead by a lightning flash.

That there frequently exists large quantities of free electricity in clouds and fogs, can be shown in a variety of ways. Probably one of the best of these is by means of some experiments made in England by a gentleman named Crosse. Crosse had been repeating Franklin's experiments of drawing electricity from the air. For this purpose he had erected a long insulating wire, suspended by means of poles that projected above the tops of the tallest trees in his park. The wire so strung over the tree-tops was more than a mile

in length. It was carefully insulated from the trees and the poles on which it was placed by means of non-conductors, and connected with his laboratory, where it was so arranged that the electricity it collected charged and discharged a Leyden jar battery containing fifty large jars.

rising in the west. They generally collect in a mass near the western horizon. From near the top of the bank of clouds, a forerunning layer of fleecy, feathery cirro-stratus clouds may be seen extending rapidly towards the east and collecting in horizontal bands in the higher regions of the atmosphere. As these clouds advance rapidly, they grow thicker on the eastern side; and a festoon of clouds begins to slowly descend and dissolve from the lower surface. In the meantime, the rain-bearing bank moves rapidly to the east. The air, which has been oppressively warm, now grows slightly cooler as the fore-running bank of clouds hides the sun. As the clouds approach, distant thunder is heard; when below the level base a gray rain curtain appears which

trails on the ground, hiding objects behind it. Small detached clouds form in front, and, rapidly increasing in size, are merged with the advancing storm-cloud which overtakes them. At the same time a ragged squall cloud, better shown in Fig. 53, of a light gray color, rolls beneath the dark cloud mass.

The storm advances broadside over the country with a velocity of twenty to fifty miles an hour. A short-lived squall

CHAPTER XXVIII

LIGHTNING AND THUNDER

Thunderstorms occur in nearly all parts of the world, except in the higher latitudes of the Arctic and the Antarctic zones.

The thunderstorms so common in the temperate zones, occurring either late in the afternoon, or early in the evening of a hot, sultry day, are called heat thunderstorms, or thun

der gusts. They belong, like cyclones, to the class of travelling storms.

Several hours before a thunderstorm bursts, peculiar rounded masses of lurid looking clouds known as thunderheads, such as are represented in Fig. 52, can be seen slowly