IV
1
2
3
In the first place, if it like you, let us set down the views of the last-mentioned author and refute them. He supposes that the planet Saturn has most influence in determining all motions of the heavenly bodies. When it presses upon the constellations next Mars, or crosses to the neighbourhood of the moon, or encounters the rays of the sun, being naturally cold and windy, it contracts and masses the atmosphere at more than one place. By and by, if Saturn absorb all the sun’s rays, there is thunder and lightning. If he has Mars in agreement, the lightning is forked. Moreover, he continues, forked and sheet lightning contain different materials. Evaporation from water or other moisture produces only gleams that threaten but stop short of striking. The hotter and drier exhalation of the earth forges the bolts of forked lightning. Beam meteors and torches, which differ from one another only in size, are produced in this same way. When any ball of air—what we call a whirlwind—encloses moist earthy matter, wherever it rushes it presents the appearance of an extended line of fire, which lasts just so long as the mass of air remains, which carries within it the supply of moist earthy matter.