When Jupiter thunders, he still seems to dominate our world, as in the days when the graceful legends of mythology flourished.
And not only does he work above ground, but, contrary to the belief of the ancients, his influence extends beneath the soil.
A great number of men were working in the mines at Himmelsfurth on July 5, 1755. They were, as often happens, working at various points along the vein of metal, and never dreaming of the events which might take place on the surface of the ground. All at once they were conscious of several very violent shocks, given in the oddest and most extravagant fashion. Some felt the shock in their backs, while their neighbours received them on their arms or legs. They might have been shaken by a mysterious invisible hand, stretching now up from below, now from above, now from the sides of the galleries. One of the miners found himself hurled against the wall, two others, whose backs were turned, almost came to blows, each believing that his mate had thumped him.
The real culprit was the thunder, of whom they might well demand an explanation of these strange proceedings.
Here is another example which bears out the foregoing:—
On the 25th of May, the watchman on guard at the pit mouth of one of the principal mines at Freyberg, perceived an electric glimmer run along the wire rope going to the bottom of the mines, and used by the miners to exchange signals with the men employed in working the lifts. Suddenly all the pits were brilliantly lit up. At the same moment the watchman saw a clear vivid flame shoot out at the other end of the chain. On this occasion the lightning behaved with due discretion, and shone through the mine without giving any one the slightest shock.
In vain the monster Tiberius, and the infamous Caligula, sought a subterranean refuge from lightning. Their impure consciences, laden with crimes, dreaded the chastisement of heaven. By fleeing from the lightning flash, they believed themselves saved from death. Lightning dogs our footsteps, and works even when the criminals believe themselves in safety. It is conceivable that the ancients should have dreaded it as an instrument of celestial justice.
Usually lightning strikes the ground with a vertical stroke, but at times obliquely, when it traces long, horizontal lines. Often the ground may be seen turned up at the foot of trees which have been struck, the sod is torn, and stones thrown to a great distance. Sometimes, too, an excavation may be seen in the ground near the object struck, of varying breadth and height. This opening may be like a funnel or hemispherical.
In a case observed on June 6, 1883, at Côte (Haute-Saône), a circular hole, having a depth of 1·20 metres, has been seen in a dyke on the declivity of the road, below a coach which was not struck.
Occasionally the hole is but the beginning of a canal, hollowed rather deeply and perpendicularly in the ground, the sides of which serve as a sheath to the fulgurite. But before treating of fulgurite tubes, which constitute the most curious phenomena in the world connected with lightning, we shall discuss certain remarkable effects observed on the surface of the ground.