Littell's Living Age/Volume 146/Issue 1884/Lightning Striking a Tree

Times Geneva correspondent writes, under date May 12, that a few days before, during a violent thunderstorm, a tall poplar on the Cour de Rive, a street in the upper part of Geneva, was struck by lightning. Directly after the occurrence Prof. Colladon made a minute examination of the tree. The professor states that it is not true, as has been commonly supposed, that the gashes (plaies) found in the trunk of a tree which has been struck by lightning are the parts with which the lightning first came into contact. The parts first struck are the highest branches, especially those most exposed to the rain. Thence it runs down the smaller branches—affecting almost the whole of them—to the larger ones, until it reaches the trunk. These larger branches, and above all the trunk, being much worse conductors than the small branches, the passage through them of the electricity produces heat and "repulsive effects," whereby the bark and sometimes the wood are torn in pieces, the bits being thrown a considerable distance, occasionally more than fifty metres. It not infrequently happens that the upper branches and their leaves are destroyed—this is generally the case with oaks, which are often struck—but the leaves and young shoots of poplars and many other trees are such excellent conductors that they do not appear when struck to suffer any notable injury. This finds full confirmation in the condition of the poplar on the Cour de Rive. In this instance the principal and highest branch of the tree on its south-western side was the first with which the lightning came in contact. Its leaves and twigs, neither withered nor tarnished, were torn into minute fragments and scattered about on the ground. This was the effect, not of the lightning, but of the concussion of air, exactly as if there had been an explosion of dynamite or gunpowder; and the windows of two houses close by were broken in the same manner and by the same cause. The presence of water near the root of a tree is often the determining cause of its attraction for the electric fluid and the professor found, five metres from the poplar, on its north side, a leaden water-pipe, and close to it a drain filled with waste water from a laundry. The principal fissure in the tree was also on the north side; and half-way between it and the water-pipe a plank lying on the ground had been pierced by a concentrated jet of the electricity as it flashed towards the pipe by the shortest route. Large trees, especially tall poplars, placed near a house, may serve as very efficient lightning conductors, but always on the indispensable condition that there is no well or running water on the opposite side of the house, for in that case the lightning, if it struck the tree, might pass through the building on its way to the water. In erecting lightning conductors it is desirable that their lower extremities should terminate in a stream, a well, or a piece of damp ground. The plant most sensible to electricity is the vine. When a stroke of lightning falls in a vineyard the leaves affected are turned red-brown or deep green, a circumstance which shows, in the opinion of Prof. Colladon, that the electricity descends in a sheet or shower,—and not in a single point, the number of vines touched—sometimes several hundred—by a single coup proving that the lightning has covered a wide area.