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<h2>CHAPTER XXVIII.</h2> 586. Why does lightning sometimes travel through a "zigzag" course? Because the electricity, being resisted in its progress by the air, flies from side to side, to find the readiest passage. 587. Why does lightning sometimes appear forked? Because, being resisted in its progress by the air, the electricity divides into two or more points, and seeks a passage in different directions. 588. Why is lightning sometimes like a lurid sheet? Because the flash is distant, and therefore we see only the reflection. [Pg 136] <hr class="bible-verse" /> "He directeth it under the whole heavens, and his lightning unto the ends of the earth." <hr class="bible-verse" /> 589. When is the flash of lightning straight? When the distance between the clouds whose electricities are meeting, is small. 590. What is the cause of the aurora borealis? The mingling of the electricities of the higher regions of the atmosphere. 591. When does the flash of lightning appear blue? When the degree of electrical excitement is intense, and general throughout the atmosphere. 592. Why does lightning sometimes appear red, at others yellow, and at others white? Because of the varying humidity, which affects the refracting power of the atmosphere. 593. Does lightning ever pass upwards from the earth to the clouds? Yes; when the earth is charged with a different electricity to that which is in the clouds. 594. Does lightning ever pass directly from the clouds to the earth? Yes; when the electricity of the clouds seeks to combine with the different electricity of the earth. The mingling of the electricities of the earth and the air must be continually going on. But lightning does not attend the phenomena, because all natural bodies, vapours, trees, animals, mountains, houses, rocks, &c., &c., act more or less as conductors between the earth and the air. It is only when there is a great disturbance of the electrical forces, that terrestrial lightning is developed. When lightning strikes the earth with great force, it sometimes produces what are called fulgurites in sandy soils; these are hollow tubes, produced by the melting of the soil. 595. What is the extent of mechanical force of lightning? Lightning has been proved, in one instance, to have struck a church with a force equal to more than 12,000 horse-power. A single horse-power, in mechanical calculations, is equivalent to raising a weight of 32,000 lbs. one foot in a minute. The force of [Pg 137] lightning, therefore, has been proved to be equal to the raising of 384,000,000 lbs. one foot in a minute. This is equal to the united power of twelve of our largest steamers, having collectively 24 engines of 500 horse-power each. The velocity of electricity is so great that it would travel round the world eight times in a minute. <hr class="bible-verse" /> "After it a voice roareth: he thundereth with the voice of his excellency; and he will not stay them when his voice is heard."—Job xxxvii. <hr class="bible-verse" /> The church alluded to was St. George's church, Leicester, a new edifice, which was completely destroyed on the 1st of August, 1846, by a thunder-storm. The steeple was rent asunder, and massive stones were hurled to a distance of thirty feet. The vane rod and top part of the spire fell down perpendicularly and carried with it all the floors of the tower. A similar disaster occurred to St. Bride's church, Fleet-street, London, about 100 years ago. The lightning first struck upon the metal vane of the steeple, and then ran down the rod and attacked the iron cramps, smashing the large stones that lay between them. The church was nearly destroyed. By the same wonderful force, ships have been disabled, trees split asunder, houses thrown down, and animals struck dead. 596. Why is it dangerous to stand near a tree during an electric storm? Because the tree is a better conductor than air, and electricity would probably strike the tree, and then pass to the person standing near. 597. If trees are good conductors, why do they not convey the electricity to the ground? Trees are only indifferent conductors, and the electricity would quit the tree to pass through any better conductor. 598. Why is it dangerous to sit near a fire during an electric storm? Because the chimney, being a tall object, and smoke a good conductor, would probably attract the electricity, and convey it to the body of a person sitting near the fire. 599. Why is it dangerous to be near water during an electric storm? Because water is a good conductor, and the vapour arising from it might attract the electricity. Man, being elevated over the water, might form the first point attacked by the electricity. 600. Are iron houses dangerous during an electric storm? No; they are very safe, because their entire surface is a good [Pg 138] conductor, and would convey the electricity harmlessly to the earth. <hr class="bible-verse" /> "To him that rideth upon the heavens of heavens, which were of old; lo, he doth send out his voice, and that a mighty voice."—Psalm lxviii. <hr class="bible-verse" /> 601. Why does electricity seize upon bell wires and iron fastenings? Because copper wires are the very best conductors of electricity; and iron articles are also good conductors. 602. Supposing electricity to attack a bell wire, where would the point of danger exist? At the extremities of the wire, where the conducting power of the wire would cease, and the electricity would seek to find another conductor. 603. Are umbrellas, with steel frames, dangerous in an electric storm? They are dangerous in some degree, because they might convey electricity to the hand, and then transfer it to the body. But, generally speaking, when it rains, the rain itself, being a good conductor, relieves the disturbance of electricity by conveying it to the ground. 604. Are iron bedsteads dangerous in electric storms? No, they are safe, because the iron frame, completely surrounding the body, and having a great capacity for conduction, would keep the electricity away from the body. 605. Why is it safe to be in bed during an electric storm? Because feathers, hair, wool, cotton, &c., especially when dry, are good insulators or non-conductors. 606. What is the safest situation to be in during an electric storm? In the centre of a room, isolated as far as possible from surrounding objects; sitting on a chair, and avoiding handling any of the conducting substances. The windows and doors should be closed, to prevent drafts of air. 607. In the open air, what is the safest situation? [Pg 139] To keep aloof, as far as possible, from elevated structures; and regard the rain, though it might saturate our clothes, as a protection against the lightning stroke, for wet clothes would supply so good a conductor, that a large amount of electricity would pass over man's body, through wet garments, and he would be quite unconscious of it. <hr class="bible-verse" /> "God thundereth marvellously with his voice: great things doeth he, which we cannot comprehend."—Job xxxvi. <hr class="bible-verse" /> During a violent electric storm in the Shetland Islands, a fishing boat was attacked by the electric fluid, which tore the mast to shivers. A fisherman was sitting by the side of the mast at the time, but he felt no shock. Upon taking out his watch, however, he found that the electric current had actually fused his watch into a mass. In this case, it is more than probable that the man was saved through the saturation of his clothes with rain. 608. Do lightning conductors "attract" electricity? Not unless the electric current lies in their vicinity. 609. Why have lightning conductors sometimes been found ineffective? Because they have been unskilfully constructed; have been too small in their dimensions, and have not been properly laid to convey the electricity harmlessly away. 610. What is the best metal for a lightning conductor? Copper, the conducting power of which is five times greater than that of iron. 611. Why should a large building have several conductors? Because the influence of a conductor over the electricity of the surrounding air does not extend to more than a radius of double the height of the conductor above the building: for instance, a conductor rising ten feet high above the building would influence the electricity twenty feet all round the conductor. 612. Why should conductors have at their base several branches penetrating the earth? To facilitate the discharge of the accumulated electricity into the earth. 613. Why does electricity affect the shapes of clouds? Because electricity does not penetrate the masses of bodies, but affects generally their surfaces. Hence electricity exists in the [Pg 140] surfaces of clouds, and in its efforts to find an equilibrium it causes the clouds to roll in heavy masses, having dark outlines. <hr class="bible-verse" /> "All ye inhabitants of the world, and dwellers on the earth, see ye, when he lifteth up an ensign on the mountains; and when he bloweth a trumpet, hear ye."—Isaiah xviii. <hr class="bible-verse" /> The fact that electricity resides in, and is conducted by, the surfaces of bodies, is well established, and should receive due attention in the protective measures adopted to secure life and property against the effects of lightning. A practical suggestion that arises out of this fact is, that tubes of copper would form far more efficient conductors than bars of the same metal. A copper tube, of half an inch diameter, would conduct nearly double the amount of electricity which could be conveyed away by a bar of copper of the same diameter. The upper extremity of the tube should be open obliquely, that the electric current might be induced to pass over both the inner and outer surfaces. <hr class="chap" /> <div style="break-after:column;"></div>

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