Chap. 52.] LIGHTNING AND ITS ErFECTS. 8L different causes ; the air, wbicL is condensed in the winter, is made still more dense by a thicker covering of clouds, while the exhalations from the earth, being all of them rigid and ft'ozen, extinguish whatever fiery vapour it may receive. It is this cause which exempts Scythia and the cold districts round it from thunder. On the other hand, the excessive heat exempts Eg^-pt ; the warm and diy vajDours of the earth being very seldom condensed, and that only into light clouds. But, in the spring and autumn, thimder is more frequent, the causes which produce summer and ^dnter being, in each season, less efhcient. From this cause thimder is more fre- quent in Italy, the air being more easily set in motion, in consequence of a milder winter and a showery summer, so that it may be said to be always spring or autumn. Also m those parts of Italy which recede from the north and lie to- wards the south, as in the district round oiu* city, and in Campania, it lightens equally both in winter and in summer, which is not the case in other situations. CHAP. 52. (51.) OF THE DIFFEEENT KINDS OF LIGHTNING^ AND THEIK WONDEEFUL EFFECTS. AYehaveaccountsof many different kinds of thunder-storms. Those which are dry do not biu-n objects, but dissipate them ; while those Avhich are moist do not biu'n, but blacken them. There is a third kind, which is called bright lightning', of a very wonderful nature, by which casks are emptied, Avithout the vessels themselves being injured, or there being any other trace left of their operation^. Gold, copper, and silver are melted, while the bags which contain them are not in the least burned, nor even the wax seal much defaced. Marcia, a lady of high rank at Bome, was struck while pregnant ; the fa?tus was destroyed, while she herself survived
ithout
1 " fiilgxir." The accoimt of the different kinds of thimder seems to be principally taken from Aristotle ; Meteor, iii. 1. Some of the phse- nomena mentioned below, which would natm-tdly appear to the ancients the most remarkable, are easily explained by a referenco to their electrical origin. ^ " quod clarum voeant." 3 This account seems to be taken from Ai'istotle, Meteor, iii. 1. p. 574 ; see also Seneca, Nat. Qusest. ii. 31. p. 711- We have an account of the pecuhar effects of thunder in Lucretius, vi. 227 et seq. VOL. I. G
