ABSTRACT
1 ALTHOUGH at any time of the year you can normally see vapours and mists, from which thunder and thunderbolts are generated by the reverberation of clouds, yet they happen most of all in summer, when they are attracted from the earth more profusely and raised to a greater height by virtue of the heat, a fact that is quite obvious to everyone. Although mist and thick vapours are ejected rather than drawn out from the bowels of the earth in winter and spring, they do not however rise as high because of lack of heat but remain in the lower air, inducing rain and wind later. In the autumn, which, as Seneca bears witness, is cold and dry, there is neither moisture to be raised nor heat to raise it, since everything is plainly consumed by very harsh frost. 1 Even though these conditions customarily happen by the general process of Nature almost everywhere throughout the world, in northern areas, as even Herodotus agrees, ominous thunders sometimes occur in winter, perhaps on account of the hot exhalations from the mines, which are plentiful in those parts, and where the veins of sulphur, as I shall relate below, in the coldest winter do not allow certain lakes to freeze at all. 2 Though these claps of thunder come at an unusual time of year, farmers and ships’ captains are not greatly astonished or disturbed by them; for, even if they judge such winter thunder as portents, they look for the effects of them only in the month when they occur. In January thunders mean higher winds than usual and taller growth of the earth’s crops.
Thunder more frequent in summer
Vapours are ejected
Autumn cold and dry
Ominous thunders in winter Veins of sulphur
Farmers and captains are not disturbed by thunder
