Part 15 (1/2)

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.