Rensselaer Union, Volume 10, Number 48, Rensselaer, Jasper County, 15 August 1878 — Danger From Lightning. [ARTICLE]

Danger From Lightning.

Under wbat conditions ia damage from lightning powerless, and what are the means by which the risk can be lessened or avoided ? An isolated tree, standing eitfcejf! Pjx>*» a wide plain or upon an eminence, is obviously likely to determine a lightning discharge, to “ attract the lightning/’ to use a common expression. The top of the tree is the nearest point to the cloud, and since the tree is a better conductor than the air, a line drawn vertically through it to the cloud’"roarks the shortest and easiest course along which the electricities may. pass. H, when the charged cloud arrives directly over this point, the ext. nsion is sufficient to overcome the resistance along th&t line, a discharge will take place and the tree will be struck. But if the tension be not sufficient, the cloud, will pass harmlessly over. Hence it appears that a person standing during a thun-der-storm beneath a tree so situated is exposed to some risk. On no aficount, therefore, should the traveler take refuge under an isolated tree; generally he will do well to avoid its neighborhood altogether; but should ne be overtaken by the storm when on a plain, with no shelter near, the tree may still be mado to afford him some protection. If ho take up a position near it, but not under its branches, he will probably escape unhurt should the lightning descend upon it. The safest distance from the tree is that which is equal to its height. To approach much nearer than this is to incur the risk of being within the influence of the stroke; to remain at a much greater distance away is to place one’s self in the same conditions of isolation as the tree itself. It will have been remarked by all observers of the phenomenon that whenever a tree has been struck by lightning it has generally occupied an isolated position. In describing the position as one of isolation, however, it is not meant that the tree is necessarily standing alone, but that it is not one of a numerous group. When there are many trees together, their collective conductivity is often sufficient to cause an indestructive discharge of the electricity. This is especially likely to happpen when the trees are wet with rain, for then their surfaces are covered with a film of water, which is a good conductor. For this reason, the danger from lightning is much less after rain has begun to fall, than before, when everything is dry. It appears, therefore, that the safest situation during a thunderstorm is in the midst of a wood, particularly if the neighborhood of the tallest trees be avoided. In such a place of shelter the travejer may take refuge in full asssurance that he will there be effectually shielded from harm. The greatest risk of injury from lightning is undoubtedly incurred by persons traveling across a wide and very flat plain, because in such a situation they are the only elevated objects. To lessen the risk, which may here be somewhat serious, advantage should be taken of whatever undulations of surface may exist, to keep upon the lowest ground. No doubt the prostrate position would in these circumstances afford greater security than the erect. It happens not unfrequently that animals are killed by lightning under a tree to which thev had betaken themselves for shelter. In these cases the tree is struck partly in consequence of its isolation, and partly on account of the presence of tho animals beneath it. Usually there are several, and often many of them assembled together, huddled probably by terror into contact one with another. The air, heated by their bodies, rises above them laden with moisture, derived mainly from their breath. Who has not noticed the cloud of vapor that in tho early morning and in certain states of the weather hangs over a flock of sheep or a herd of kine? The column of moist air ascending through the branches of the tree toward the clouds offers, in consequence of the comparatively high conductivity of water, favorable passage for the electricity. A herd of cattle under an isolated tree is thus exposed to a double risk; also, it is evident that these animals are in the open country less secure from injury than human beings, who cannot affect the atmosphere in a like degree.—Chambers' Journal.