Year: 1878

Daring thunderstorm we may nouce


that buildings having a rod of metal des-


cending from their highest point into the


earth, called "lightniDg conductors" are


not injured by the storm. Can we explain


the reason of this. We have seen by our


experiments that electricity passes away


from q conductor il it is connected by a


metal chain with the earth, but not if it


is connected by glass. Let us now work


our machine till we get spark when we


bring our finger near it. If we now take


metal rod in our hand, and hold it close to


our finger, 30 that it's end comedies with


the point of the finger, and bring both near


the prime conductor of our machine. we


shall find we cannot now get spark to


touch the finger; it will invariably pass


to the metal rod, and if the rod be long


enough to reach the ground, the e'ectlici-


ty will not pass through our body at all,


but pass straight to the earth by the metal


rod. If, however, instead of metal rod


we take glass one, ard use it In the same


way, the result will be very different. Now


we shall not be able to get epaIk to


touch the glass at all it will invariably


strike the finger, and pass through our


body to the ground. If, therefore, we


have a metal rod standing fixed in the


ground beside us during thunder storm


a fiaeh of lightning coming, would, like
the spark from the conductor, pick out


the METAL rod and pass by it harmlessiy to


the ground, leaving us untouched. Oo
| the other hard, were a glass rod beside US,
the lightning would leave the glass rod
untouched, and pass through our bodies
| to the ground, most likely oepriving Us OF
| life in the passage. This Is the whole
principle of lightning conductors. We ez
prees it by saying that electricity aiways
passes by the best conductors. Knowing,
| as we do, that metals are better conduct


ors than stone, wood, etc., of which ouI


buildings are composed, we protect them
| I'D ol ,F1nnk kaH IFh
| the ground to their highest point. 1t it
found by experience that rod erected in
| this way protects space all around it


equal to twice its height. Thus q rod
| so feet high protects q space of 100 feet on


every side of it. From the knowledge OF


the principals of lightning conductors, we
may know the positions of safety. The


French parGgreIes are also other forms OF
! lightning rods. They are em I'll conductors
| set up by means of poles in the vineyards
| in France, TO draw off the electricity from
| the atmosphere ever them, and thus pre-
vent the accumulatiops which, when they
| occurred, were found to generate hail
| storms. Arago proposed that these conduct
| ors should be raised and supported by email
| batteries connected by means Of slender
wires or chains with the ground. This plan,
| like some other ingenious applications OF
electricity, was found to act perfectly wefl
| in theory, but proved impracticable, owing
| to the great expense of setting up and


maintaining such q system over any great
extent of country. Cases have been known
| ia which a gold pin in girls hair has been
| fused by lightning, OF a bracelet melted off
| lady's wrist, without the wearer'S suffer
ing any actual injury. Sportsmen, owing
to the iron of their weapons, are apt to be


struck by lightning. Hence, some philos-


opher-half in jest, half in earnest-has


proposed that a portable lightning rod in
connection with an umbrella should be
provided for people liable to be caught in
thunder storms. Such q pGrGpLuie, if the


ferrule were provided with pointed me-
talic rod projecting into the air, and con-


nected with detachable chain or wire to
drag on the ground behind, could bring the


bearer and his paraphernalia Of destruction


safely through the electric tempest, even


though the lightning should play all round


him. We must keep away from the
neighborhood of bad or non-conductoTs,
and near to good ones, if they are connect


ed with the ground, A man clad in the


steel armour cf the Middle Ages would be


almost perfectly safe, especially if he had


steel points on his boots to stick into the
ground, as he would have a capital conduc-
tor all around him. For the came reason,
a man in an iron bed will be safe, espec'


nlIv if the bed be connected by metal to the
gas pipe, so as to make complete contact


With the earth. Standing near high body