76 THE EFFECTS OF LIGHTNING. 



by an explosion, the whole conductor is rendered luminous, which never hap- 

 pens when the conductor is uninterrupted. 



Lightning struck the conductor on the house of Mr. West, in Philadelphia, 

 and the place where its lower extremity met the ground, at about five feet be- 

 low the surface, being dry, the lightning escaped by explosion. A heavy 

 shower fell at the moment, which having moistened the pavement, the whole sur- 

 face of the ground for several yards around the conductor seemed to be on fire. 



VIII. EFFECTS PROCEEDING FROM THE SURFACE OF THE EARTH. 



The class of appearances now to be noticed require the more detailed and 

 especial description, inasmuch as they are more rarely subjects of observation, 

 and many of them are difficult to be connected with the known principles of 

 electricity. 



When storms are breaking in the heavens, and sometimes long before their 

 commencement, and when their approach has not yet been manifested by any 

 appearances in the firmament, phenomena are observed, apparently sympathetic, 

 proceeding from the deep recesses of the earth, and exhibited under very various 

 forms at its surface. Instead of recounting this extraordinary class of physi- 

 cal facts in general terms, which from their nature must want that precision so 

 desirable in such descriptions, and which are always liable to inaccuracy when 

 a legitimate theory of the phenomena is wanting, we shall here state the par- 

 ticular facts collected by the active zeal of M. Arago on this interesting sub- 

 ject. 



DAVINI wrote to VALLISNERI that he had observed, near Modena, a fountain 

 whose waters were clear or turbid according as the sky was clear or clouded. 

 Vallisneri himself states that he observed that the salt marshes of Zibia, Que- 

 veola, Cassola, and also in the duchy of Modena, and the sulphur springs, an- 

 nounce an approaching storm before there is any appearance of it in the heavens, 

 by a sort of ebullition, and by subterranean noises like that of thunder, and 

 sometimes even by actual thunder. 



TOALDO relates that in the hills of Vicentino, at a little distance from the 

 parish church of Molvena. there is a fountain called by the people of the place 

 Bifoccio, because it has two sources. When a storm is approaching, this foun- 

 tain, even after a long drought and at times when it is completely dry, gushes 

 out suddenly and fills a large canal with turbid water, which spreads over the 

 adjacent valleys. 



At two miles from the source of this fountain, near the parish church of 

 Villa-raspa, in the court-yard of M. Joseph Pigati, of Vicenza, is a deep well 

 which, on the approach of a storm, boils with such violence as to terrify the 

 inhabitants of the place. 



It is stated in the journal of Brugnatetti, that, on the 19th of July, 1824, in> 

 mediately after a storm, the waters of the lake Massaciuccoli, in the duchy of 

 Lucca, became as white as if a quantity of soap had been dissolved in them. 

 This appearance continued during the following day, and on the next day mul- 

 titudes of fish of every size were found dead upon its banks. 



No one who has witnessed the local floods which take place in storms of 

 thunder and rain can fail to be struck with the inadequacy of the quantity of 

 rain, however highly estimated, which can fall within given limits, to account 

 for the enormous quantity of water discharged over plains and through valleys 

 from the higher regions. Direct evidence is not, however, wanting to prove, 

 that in such cases the internal waters of the earth are often discharged through 

 temporary fissures, which break open in the sides of hills and other places. 

 An occurrence of this kind took place in Yorkshire, in the month of June, 



