In 1835, an old beech tree was struck in the forest of Villers-Cotterets. This venerable patriarch was more than three hundred years old. Of its upper branches, which were wide and strong, four of the finest were destroyed; a fifth, stripped of its bark to a great extent, was not torn off the trunk. The trunk was split where the other four branches were torn from it. The interior of it was blackened and slightly carbonized.
On July 15, 1868, at Chefresne, canton de Percy (Manche), an oak and an ash were struck by lightning within five minutes of each other.
On August 10, 1886, at Haute-Croix, in Brabant, an ash was struck and destroyed. On August 23, in the same year, an ash was struck also at Namur.
The box tree and the Virginian creeper used to be regarded as safeguards against lightning. The same virtue was attributed to the house-leek, a thick herbaceous plant, which grows usually upon walls and roofs, and which the Germans call Donnerblatt or Donnerbarb, Thunder-leaf or Thunder-beard.
According to some authors, again, lightning never strikes resinous trees, such as pines or firs. But this also is disproved by the facts, especially in regard to firs.
Among the many particulars I have collected of recent years, is the following list of sixty-five different kinds of trees, with the record of the number of times each species has been struck by lightning within a given period:--
54 oaks.
24 poplars.
14 elms.
11 walnut trees.
10 firs.
7 willows.
6 pine trees.
6 ash trees.
6 beech trees.
4 pear trees.
4 cherry trees.
4 chestnut trees.
3 catalpas.
2 lime trees.
2 apple trees.
1 mountain ash.
1 mulberry tree.
1 alder.
1 laburnum.
1 acacia.
1 pseudo-acacia.
1 fig tree.
1 orange tree 1 olive tree.
0 birch.
0 maple.
Height obviously accounts for a good deal. It is incontestable that, in the case of a clump of trees standing in the middle of a plain, lightning will in most cases pick out the tallest. But this is not an absolute rule. The isolation of trees, their qualities as conductors, the degree of moisture in the soil in which they are rooted, their distance from the storm clouds, the character of their foliage and of their roots--all these things are important factors.
Numerous experiments have been made with a view to ascertaining the amount of resistance offered to the electric spark by different kinds of wood. Similar pieces of beech and oak have been exposed lengthwise to the electric spark given out by one of Holtz"s machines, with the result that the oak wood was pierced by the electric fluid after one or two revolutions of the machine, whereas for the beech wood a dozen or twenty were needed. Black poplar wood and willow offer a moderate resistance: a few revolutions suffice to penetrate them.
In all instances the susceptibility of the wood depends on the sap. It has been proved by a.n.a.lysis that the woods which contain starch with but little oil, such as the oak, poplar, willow, maple, elm, and ash, offer much less resistance to the electric current than those trees which are richer in fatty matter, as the beech tree, walnut tree, lime tree, birch tree, and so on.
These conclusions are corroborated by the case of the pine tree, the wood of which has a great quant.i.ty of oil in winter, but in summer lacks it as much as those trees which contain more starch.
Experiments have proved that in summer this wood is quite as likely to serve as a conductor as the oak; while in winter its resistance to the electric spark equals that of the beech and other trees which are rarely struck by lightning. Decayed trees are excellent conductors of electricity; those in full vigour being much more rarely struck.
In any case, it has been proved that the effects of lightning are particularly severe in the vegetable world. It has been pointed out elsewhere in this little book to what dangers those persons are exposed who take shelter beneath the trees during a thunderstorm; there are innumerable examples of the imprudence of taking refuge from the rain under thick foliage, people having been killed by a fireball--for lightning does not always take the trouble to make a selection, sparing neither the protector nor the protected.
We shall give some more instances, chosen from a considerable number of similar observations.
In 1888, ten reapers, surprised by drops of rain and distant rumbling of thunder, left their work and took refuge beneath a big walnut tree.
But one of them having questioned the security of this retreat, all immediately fled in the direction of a neighbouring wood, except one young girl of fourteen years. Several who returned to advise her to follow them, saw her smilingly throw her arms round the trunk of the tree, and almost at once fall backwards, her arms extended. She was dead.
On the 22nd of August in the same year, four labourers, returning from work, were overtaken by a thunderstorm. Three of them stopped under an elm, the fourth prudently continued on his way. Well it was for him.
Several minutes later, the lightning struck the tree, killing two of the labourers outright, and grievously wounding the third. The latter was found almost completely naked; his garments, burnt and tattered, were scattered round him. When he came to himself, he was in such a violent delirium that it was necessary for several men to bring the unfortunate victim to his home, where he died shortly afterwards in the most horrible agony.
About six o"clock, on the 23rd of June, seven men employed on the farm of Puy-Crouel, were working in a field of beet-root. Overcome with the heat, they went into the shade of a walnut tree. All at once, a flash of lightning illumined the sky; the seven workmen were thrown down, one of them being hurled several yards away. Three of them were able to get up and go to the farm, the others were severely burnt, and half asphyxiated. One of the victims had his back skinned the whole length of the vertebral column; the other had his face scratched, as if torn by fingernails. All had lost their memory. The walnut tree under which they had sheltered was cleft from top to bottom.
Here is another example no less terrible--
Seven children, belonging to Ahrens, were caught in a thunderstorm as they were coming home from the fields, and took shelter under a tree.
The lightning killed the seven little people.
Another time, four young men taking refuge under an oak, were struck and thrown down. One of them was killed instantly, his companions were cruelly injured.
On the 10th of July, in Belgium, a woman gathering cherries was killed on a tree which attracted the fluid. A young man standing beneath it was paralyzed.
We might multiply these tragic tales; each year a number of similar cases happen. The imprudence of human beings is truly incorrigible!
Everybody, however feeble his instinct of self-preservation, should flee the vicinity of trees during a thunderstorm, and allow himself to be drenched on the road, rather than offer his life as a too generous burnt-offering to the lightning, for the oak"s robust trunk, or that of the poplar, elegantly plumed with its graceful foliage, may be the altar on which the sacrifices in honour of Jupiter are made.
The wood of trees is not so good a conductor of electricity as the human body. For this reason, a person leaning against a tree receives the full discharge; at times the tree is splintered, because it did not serve as a perfect conductor.
Yet the conductive power of certain species is so remarkable, that the neighbourhood of particular trees may be regarded as a protection against lightning (this, however, without coming in contact with them!).
The tips of the branches pointing towards the clouds, and the moisture they receive, undoubtedly influence the electricity of the atmosphere; and, moreover, by means of these graceful branches, an inaudible but continual exchange is effected between the electricity of the earth and sky, thus holding the balance between two opposite charges.
Colladon a.s.serts that poplars planted near houses may, in favourable conditions, act as lightning conductors, on account of their height and powers of conducting. He adds that it is necessary to take other circ.u.mstances regarding the situation of the dwelling into account, which are not always easy to define. Their protection of the neighbourhood is not constantly the same. For it to be effectual, the foliage should be very low, and they should be at least two metres distant from the roof and walls. Their roots, too, should be in a damp soil, and metal should not enter largely into the construction of the neighbouring houses. In these conditions, poplars may fulfil the useful functions of lightning conductors.
At times, during a storm, several trees are struck by the same flash.
For instance, on May 23, 1886, in Belgium, three poplars were blasted by a single thunderbolt.
On the other hand, trees planted in lines are sometimes struck alternately. A case occurred where the lightning seemed to have taken aim and touched all the odd numbers in a row without striking the others.
Certain plantations act on the fluid with an extraordinary intensity.
At Lovenjoul, in Belgium, a wood of undergrowth and big trees, planted in marshy ground, seems to possess this singular privilege, and the agriculturists of the country declare that no storm ever pa.s.ses their way without lightning falling there. In the middle of this wood one can count seven oaks, near to one another, struck by it. Not far off, a huge ash, and a little farther away two poplars, likewise blasted.
All the trees have not been struck in the same way; some are scorched or stripped of their leaves; the others have their trunks perforated, or split in different parts. Usually trees are cleft from top to bottom; in some cases the furrow is horizontal or perpendicular in the direction of the branches.
Pieces of bark or of wood are sometimes torn off lengthwise, and only adhere to the trunk in strips here and there. But that does not prove conclusively that the lightning struck upwards from the ground; it may have rebounded (?) after striking from above.
Certain effects, however, can only be explained by an ascending movement of the fluid. The following cases for example:--
"During the summer of 1787, two men were sheltering under a tree at Tancon, Beaujolais, when they were struck by lightning. One of them was killed on the spot, the other felt no ill effects other than momentary suffocation. Their horses were caught up to the top of the tree. An iron ring which bound the wooden shoe belonging to one of the men, was found hanging from a high branch of the same tree. Now, at a little distance, there was a tree which had also suffered greatly by the pa.s.sage of the electric fluid. In the soil at its base a round hole was to be seen, shaped like a funnel. Directly above it the bark had been loosened and slit into slender thongs. As for the tree beneath which the men had sheltered, it also had half its bark off, and long splinters were to be seen hanging only by the upper parts. On one side of the tree the leaves were withered, on the other they were still quite green."
In this most remarkable instance the lightning had come out of the ground.