Professor Colladon, of Geneva, has made some interesting observations on
the course of lightning when it strikes trees and houses. He holds that the great discharges which injure trees and houses seldom or never happen while the light- ning has an unobstructed course,—which it has along the thin upper branches of trees, where birds and their nests are often left quite uninjured by its descent. But it is where the electric current reaches the thick stem that the tree becomes a worse and worse conductor, and it is here, therefore, that the tree is what is called struck,—i.e., here that the electricity, failing to find an unobstructed channel to the earth, accumulates in masses, and gives out shocks which rend the tree. And the same is true of houses whose lightning-conductors stop short of the ground. Professor Colladon has also shown that the close neighbourhood of a pool of water is a great attraction to the electric current, and that the electricity often passes down a house or tree till it is near enough to dart straight across to the water; and be thinks that where possible, lightning-conductors should end in a spring or pool of water. Professor Colladon believes that lightning descends rather in a shower,—through a multitude of vines, for instance, in the same vineyard,— than in a single main stream. It divides itself among all the upper branches of a tree, and is received from hundreds of atmospheric points at once, instead of, its has been usually supposed, from one. Electricity is a rain, a number of tribu- taries from a wide surface, not a single torrent.
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