THE EFFECTS OF LIGHTNING. 



75 



course being confined to a series of accidental conductors supplied by the 

 walls and furniture. 



In 1759 the detachment of French soldiers which conducted Captain Dibden 

 a prisoner of war at Martinique, took shelter from rain under the wall of a 

 small church which had neither tower nor steeple. Lightning struck the 

 building, killed two of the soldiers leaning against the wall, and made a breach 

 in the wall, immediately behind them, four feet high and three feet wide. On 

 examining the place, it was found that within the chapel, at the place of the 

 breach, a collection of massive bars of iron were placed, intended to support 

 a monument. Those soldiers who were not placed opposite to the iron were 

 uninjured. 



On the 10th of June, 1764, lightning struck the steeple of St. Bride's church, 

 in Fleet street, London, and did great damage. The weathercock was first 

 struck ; from that the lightning descended along a bar of iron buried among 

 the massive stones of which the steeple is built. This bar was two inches in 

 diameter, and twenty feet long, and its lower end was let into a cavity five 

 inches deep in a stone, and secured there by lead. The gilding on the cross 

 and weathercock was partly destroyed, and all that remained was blackened. 

 The soldering in several places was fused. Along the descending bar no trace 

 of the fluid was discoverable ; but at its lower extremity, where the continuity 

 of the metal was broken, were marks of violent effects. The stone in which 

 the end of the bar was inserted was broken in pieces : a large breach was 

 made at the same place in the side of the steeple. The lightning thence 

 seemed to have descended by leaps from one iron cramp to another immedi- 

 ately below it. It did not, however, confine its path merely to the descending 

 direction : wherever iron cramps were inserted within the masonry, to bind 

 the blocks of stone together, the fulminating fluid penetrated and left its marks. 

 In fine, the stones were split, broken, pulverized, displaced, and launched to a 

 distance like projectiles, in the neighborhood of the extremities of all the bars 

 of iron used in the construction of the building. 



In the case of the house struck in 1767, in the Rue Plummet, in Paris, already 

 mentioned, a remarkable example of the influence of a hidden mass of iron was 

 offered. The only injury done to the exterior of the building was the entire 

 demolition of the entablature, behind which was disclosed a number of large 

 pieces of iron used in its construction. 



It is evident from these instances, that so long as a continuity of metal is 

 afforded, no damage is done by lightning. But a continuity of any conducting 

 matter ought to produce the same effect. 



If the metal be continued to the ground, and the ground be sufficiently hu- 

 mid to afford a free passage to the electricity, no injurious effects ensue, and 

 the lightning passes quietly into the crust of the globe. But if the ground be 

 dry, it becomes a non-conductor, and the electricity escapes with an explosion. 



On the 28th of August, 1760, lightning struck a bar of iron erected on the 

 roof of the house of Mr. Maine, in the United States, and partially fused it. 

 This bar descended to the ground, which it penetrated to some depth, but the 

 soil not being sufficiently humid, the lightning produced an explosion, broke 

 up the ground, and damaged the foundations of the house. 



On the 5th of September, 1779, at Manheim, on the Rhine, lightning struck 

 an iron bar raised on the roof of the hotel of the ambassador of Saxony, by 

 which it was conducted along the roof and walls of the building to the ground. 

 The ground being dry, it quitted the bar with an explosion which produced a 

 vortex of sand which was witnessed by several persons, and of which evident 

 traces remained. 



When the continuity of the conductor is broken, and the lightning escapes \ 



