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and a corning house at Mazagon, not liavhig Vigldiring rods^ 

 ■were struck by lightning and blown up. But no such instance 

 of magazines preserved bj rods for seventy yesrs has occurred. 



No supposition can be naore erroneous than that -which 

 ascribes to a well constructed lightning rod the power of draw- 

 ing the thunder cloud into its vicinity. An experiment by Dr, 

 Franklin sets this matter in its proper light. He insulated a 

 scale beam hung on a vertical pivot, from which one of the 

 scales had been removed, and into the other a light bunch of 

 cotton wool had been placed. He then charged the beam with 

 positive electricity, giving it at the same time a horizontal 

 rotatory motion over the surface of a table ; when he placed 

 beneath the scale as it revolved a piece of blunt iron, the scale 

 descended towards the iron to give off its explosive discharge ; 

 but when he substituted an iron point for the blunt iron, instead 

 of descending, the scale, having lost its electricity to the iron 

 point, rose quickly above the table. Thus a cloud, instead of 

 approaching a forest of lightning rods in a village, would be 

 deprived of the electricity which has kept it so near the earth 

 by attraction and ascend in consequence of the loss of it. 



That the confidence so generally felt in the efficacy of the 

 protection of lightning rods, is not misplaced, has been tri- 

 umphantly proved in cases innumerable. 



In 1769, the Jacob tower, in Hamburg, was furnished with 

 a rod ; and after the cathedral at Sienna had been repeatedly 

 struck by lightning the authorities concluded to follow the 

 example of Hamburg, and erected conductors. The inhabit- 

 ants at first regarded them with great terror, and stigmatized 

 them as heretical. But on the 10th of April, 1777, a heavy 

 shock of lightning visited the tower and glided harmlessly to 

 the earth ; the church has not been injured since, and the con- 

 ductors are absolved from the charge of heresy. 



Old St. Paul's church in London, unprotected by rods, was 

 twice struck and damaged. The present structure, though more 

 elevated, being provided with rods, has never suffered from 

 electricity. 



The cathedral of Geneva, the most elevated in the city, has 

 for more than two centuries enjoyed perfect immunity from 

 lightning ; while the neighboring bell tower of St.Gervais, though 

 not so elevated, has often been struck and damaged. In 1771, 

 Saussure hy examination discovered the cause to consist in a 

 complete coating of tin plate from the top of the Cathredal 

 spire to the base of the tower, thence by metallic water pipes to 



