NATURAL PHILOSOPHY. 1C3 



finding the foot of the lightning-conductor dipping in a subterra- 

 nean sheet of water, immediately escapes that way, being attracted 

 by the contrary fluid overhead; it accumulates at the summit or 

 point of the conductor. If the latter is gilt or made of platinum, 

 the fluid, attracted by the cloud, exercises on the atmosphere, 

 which is a bad conductor, a pressure sufficient to enable it (the 

 electric fluid) to escape in the shape of a luminous egret, visible 

 in the dark. This egret is rarely more than 20 centimetres in. 

 length. The air becomes strongly electrified thereby, and its 

 particles arc undoubtedly conveyed by attraction to the cloud, 

 where they neutralize a part of the fluid it contains. It is this 

 neutralization which constitutes the protecting or preventive 

 action of the conductor. While the egret is formed, the influx of 

 electricity is often so intense as to melt the point, in which case 

 both the gold and platinum will trickle down the copper or iron 

 rod to which they were attached, though platinum is the least 

 fusible metal we know. In this state, however, the lightning- 

 conductor is by no means rendered unfit for service, provided 

 there be no solution of continuity ; and provided, also, its lower 

 extremity communicates freely with the sheet of water. A point, 

 therefore, is not absolutely necessary, and the commission pro- 

 pose that a copper cylinder, 2 centimetres in diameter by 20 or 

 25 in length, be substituted for it, as this cannot melt, owing to 

 its great conducting power. Lightning-conductors thus con- 

 structed should never be placed on the powder magazine, but 

 outside the round-way; there should be 3, 5 metres in height, 

 fixed to supports 15 metres high, and connected together by a 

 metallic circuit joining their lower extremities." 







DEATHS BY LIGHTNING. 



Few people are aware how many are the deaths from lightning. 

 It appears, from statistics kept in France, that during the last 

 30 years more than 10,000 people were struck by lightning, 

 of whom 2,252 were killed outright. 880 were killed during 

 the last 10 years, and of these only 243 were females. If ligh 

 ning falls on a crowd it does more mischief among the men 

 than among the women, the taller persons being most exposed. 

 Again, animals are frequently stricken, while the persons in 

 charge of them are spared. The old idea that the beech-tree is a 

 protection is a fatal error, the neighborhood of all isolated trees 

 l3cing dangerous, except when they are in metallic connection 

 with the soil. Railroads and telegraph wires are protectors, in so 

 far as they are able to absorb and convey considerable amounts 

 of electricity. Every locomotive does this un perceived, its me- 

 tallic mass being an excellent conductor. Walking along a rail- 

 road track where it runs through a country without trees is as 

 dangerous as taking shelter under a tall tree. That windows are 

 dangerous is believed to be an error, for experience does not 

 show that lightning strikes through open windows or follows a 

 draft of air. 



