OPTICAL PHENOMENA. 



521 



daring the fury of the tempest and inviting down its vengeance. The fine tower of 

 St. Mark's at Venice, rising to the height of 360 feet, terminates in a pyramid which was 

 severely injured in 1388. In 1417 the pyramid was again struck, and set on fire, having 

 been constructed of wood. The same event happened in 1489, when it was entirely 



consumed. After being rebuilt of stone, 

 the fell lightning renewed its destruc 

 tive stroke in 1548, 1565, 1653, and 

 1745 ; and on the last occasion the whole 

 tower was rent in thirty-seven places, 

 and almost destroyed. It was again ra 

 vaged in 1761 and 1762, but in 1766 a 

 lightning rod was put up, which has 

 since protected it from damage. At 

 Glogau, in Silesia, an interesting exam 

 ple of the value of conductors occurred 

 in the year 1782. On the 8th of May, 

 about eight o'clock in the evening, a 

 thunder-storm from the west approached 

 the powder magazine established in the 

 Galgnuburg. An intensely vivid flash 

 of lightning took place, accompanied 

 instantly with such a tremendous peal 

 of thunder, that the sentinel on duty 

 was stupified, and remained for awhile 

 senseless, but no disaster occurred. Some 

 labourers at a short distance from the 

 magazine saw the lightning issue from 

 the cloud, and strike the point of the 

 conductor, which conveyed it in safety 

 by the combustible material. A different 

 result took place with reference to a 

 large quantity of unprotected ammunition, belonging to the republic of Venice, deposited 

 in the vaults of the church of St. Nazaire, at Brescia. The church was struck with 

 lightning in the month of August, 1767, and the electric fluid, descending to the vaults, 

 exploded upwards of 207,600 Ibs. of powder, reducing nearly one-sixth of the fine city to 

 ruins, and destroying about 3000 of the inhabitants. Pointed hills, projecting rocks, 

 elevated buildings, and tall trees, especially if they are isolated, are particularly liable to 

 be struck, and hence it is a good general maxim in a thunder-storm, not to take a position 

 either under a tree or close to a lofty edifice, but to keep as much as possible in the open 

 country. The inhabitants of Switzerland and other mountainous countries, know by 

 experience that they have nothing to fear from thunder-storms, while in the deep and 

 close valleys. The clouds never descend to their bottom ; and the lightning alone strikes 

 the hills, or objects upon them. 



For ages the inhabitants of the globe have seen the lightning flash, and heard the 

 thunder rattle ; and some writers upon the occult sciences of the ancients, as Salverte, 

 have supposed that, tutored by experience, without any understanding of the theory of 

 the subject, they possessed the secret of warding off" from their buildings the thunderbolt, 

 by a conducting apparatus. It is certain that extraordinary intimations to this effect may 

 be culled from their writings. Pliny states that Tullus Hostilius, practising Numa's art 

 of bringing down fire from heaven, and performing it incorrectly, was struck with 



Tower of St. Mark's, Venice. 



