Thunder and Lightning Part 23

Thus, on April 13, 1863, a telegraph clerk was engaged with several other employees repairing some telegraph wires in the station at Pontarlier, when all at once they felt, at the knee-joints more particularly, a violent shock which made them bend their legs as if they had been struck with a stick; one of them was even thrown down.

No doubt the fluid reached the wires, which in those remote parts was in charge of the clerks.

On September 8, 1848, during a violent thunderstorm, two telegraph poles were thrown down at Zara in Dalmatia. Two hours later, as they were being set up again, a couple of artillerymen, having seized the wire, felt slight electric shocks, then suddenly found themselves flat on the ground. Both had their hands burnt; one indeed, gave no sign of life; the other, in trying to raise himself up, fell back as soon as his arm came in contact with that of one of his comrades, who ran to his a.s.sistance on hearing him cry for help. The latter thrown down in turn, felt his nerves tingle, and giddiness seize him, with singing in his ears. When his arm was uncovered, there was a superficial burn just on the spot where he had been touched.

On May 9, 1867, lightning fell on the road from Bastogne to Houffalize (Luxembourg), attracted by the telegraph wire, which it destroyed for about a kilometre. At a certain part, and over a length of about twenty metres, the wire was cut in small pieces, three or four centimetres long, which were scattered over the ground, and were as black and as fragile as charcoal. The poles which supported them, and several poplars planted on the same side of the road, were more or less damaged.

It has been observed that trees planted on the same side as a telegraph line were sometimes blasted on a level with the wires. It is the same with houses near the copper threads along which human thoughts take wing. Thus, at Chateauneuf-Martignes, on August 25, 1900, lightning destroyed the telegraph poles on the outskirts of the railway-station. A severe shock, like an electrical discharge, was felt at the same moment by two people who were in bed, not far from where the wire was fixed in the wall of the house, which was a very low one. The same phenomenon had been felt there already.

In the railway-stations, as well as in the telegraph and telephone offices, curious results of the spark pa.s.sing at a certain distance, or even in the immediate neighbourhood, are sometimes observed.

On May 17, 1852, towards five o'clock, the sky looking overcast, the station-master at Havre warned his colleague at Beuzeville that it would be well to put his apparatus in connection with the ground.

Beuzeville is twenty-five kilometres away from Havre, and at the former station the weather then did not look at all threatening. But clouds soon piled up, driven before a violent wind. Suddenly three awful peals of thunder succeeded each other in quick succession. With the last, lightning struck a farm about a kilometre from the station, and at the same moment a globe of fire of a reddish brown, and apparently about the size of a small bomb-sh.e.l.l, rose as if out of a clump of trees. It glided through the air like an aerolite, and leaving behind it a train of light. At a hundred metres or so from the station, it alighted like a bird on the telegraph wires, then disappeared with the rapidity of lightning, leaving no trace of its pa.s.sage, either on the wires or the station. But at Beuzeville several interesting phenomena were observed. Firstly, the needles turned rapidly, with a grating noise like that of a turnspit suddenly running down, or like a grindstone sharpening iron, which emits sparks. A great number, indeed, flew out of the apparatus. One of the needles, that on the Rouen side, went out of order; all the screws on that part of the instrument were unscrewed, and on the copper dial near the axis of the needle, there was a hole through which one could pa.s.s a grain of corn.

The instruments at Havre were unaffected. The needle remained as usual, also the dial, screws, and so on.

One of our correspondents has sent me the following very interesting communication:--

"On June 26, 1901, having rung up at the central telephone-office at St. Pierre, Martinique, a harsh noise was heard, which was almost immediately succeeded by the appearance of a ball of fire, having an apparent diameter of twenty centimetres, and the brilliancy of an electric light of twenty candle power. This voluminous globe followed the telephone wire towards the instrument. Arrived near the receiver, it burst with a terrific explosion. The witness of this phenomenon felt a severe shock, and dizziness. Recovered from his stupefaction, he noted the following facts: the telephone apparatus was completely burnt, the relay of Morse's installation was slightly damaged. The electrical tension must have been enormous, for the wire of the bobbins was, to a great extent, melted."

This latter effect, however, occurs very frequently. Not only does the lightning melt and break the telegraph wires, but it injures the poles which support them.

These are sometimes broken, split, thrown down, burst, or splintered, sometimes into threads or shavings. Poles which have been blasted are often to be seen alternating with others which are uninjured. Thus, on the line from Philadelphia to New York, during a great storm, every alternate pole up to eight was broken or thrown down; the odd numbers were uninjured. We have mentioned a similar case already.

There are several accounts, too, of lightning in pursuit of trains.

On June 1, 1903, travellers by train from Carhaix to Morlaix, between Sorignac and Le Cloistre, saw lightning follow the train over a course of six kilometres, breaking or splitting several telegraph poles.

This feat has been observed more than once. The train is escorted by lightning flashes which succeed each other almost without cessation, and the travellers seem to be whirled through an ocean of flame.

Lightning rarely strikes the carriages; only on one occasion did it actually wreck one, by breaking a wheel. The mutilated coach, however, continued to hobble along until the injury was discovered.

Generally the fluid is content to wander about the rails, to the great terror of the pa.s.sengers who witness this display of rather alarming magic. It spreads itself over ma.s.ses of iron, as for instance the roofs and balconies in Paris, without striking any particular point.

The danger would be greater to a cyclist on a road. In the suburbs of Brussels, on July 2, 1904, a cyclist named Jean Ollivier, aged twenty-one years, was riding during a violent storm, when suddenly he was struck and killed on the spot.

We shall end this description of the whims and caprices of lightning by a notice of the blasting of a German military balloon. It happened in June, 1902. The aeronaut, whose car was steered by a sub-lieutenant, was held captive, and soared at a height of about 500 metres above the fortifications at Lechfeld, near Ingolstadt. All at once the aerial skiff was touched by an electric spark, caught fire, and began to descend, slowly at first, then swiftly. The aeronaut had the good luck to get off with a broken thigh. The five a.s.sistants, who worked the windla.s.s and the telephone, also received shocks transmitted through the metal wires of the cable. They fell unconscious, but were quickly restored. This phenomenon, which is excessively rare, fittingly closes this odd collection of stories, fantastically ill.u.s.trated by lightning.

A communication from Berlin also mentions that the captive balloon of the battalion of aeronauts was struck by lightning on the exercise ground at Senne. Two under-officers and a private were wounded by the explosion.

CHAPTER IX

LIGHTNING CONDUCTORS

Until comparatively recent times, as we have seen, all that was known about thunderstorms was that they occurred pretty well all over the world, and generally in either spring or summer.

While efforts were being made on our old continent to establish by long and ingenious dissertations the exact degrees of relationship between lightning and the sparks given out by machines, in America practical experiments were being set about towards solving the problems of electricity.

Franklin it was who hit upon the idea of extracting electricity from the clouds for the purpose of investigation.

This man of immortal genius, who by his achievements in science, his n.o.ble character, and his devotion to his country, has won the admiration and grat.i.tude of posterity, was of humble origin.

The son of a soap manufacturer in a small way of business, Benjamin Franklin was born at Boston in 1706. His parents had intended him to go in for science. He was successively an apprentice to a candle manufacturer, a journeyman printer, the head of a big printing firm in Philadelphia, deputy to Congress, an amba.s.sador, and finally President of the a.s.sembly of the States of Pennsylvania. His political record was a great one. No one ever rendered greater services to his country than the diplomatist who signed the peace of 1783, and insured the independence of the United States.

It was towards the age of forty that Franklin began his study of electricity. Here is his own account of the memorable experiments to which he owed the greater part of his immense fame:--

"In 1746 I met at Boston a certain Dr. Spence, who came from Scotland.

He performed some electrical experiments before me. They were not very perfect, as he was not a man of great ability; but as the subject was new to me they surprised me and interested me in an equal degree.

Shortly after my return to Philadelphia, our librarian received as a gift from Pierre Collinson, a member of the Royal Society of London, a tube of gla.s.s, together with certain written instructions as to the way in which it should be used for experiments. I seized eagerly on the chance of reproducing what I had seen done at Boston, and with practice I acquired a great facility in performing the experiments indicated to us from England and in devising other ones. I say 'with practice,' because many people came to my house to witness these marvels."

After making several discoveries in regard to electricity, Franklin took it into his head to extract the fluid direct from the clouds. He had established the fact that a stem of pointed metal, placed at a great height--on the summit of a building, for instance--served as an attraction to lightning and guided it into the way prepared for it. He had been looking eagerly to the erection of a clock-tower which was being built at this time at Philadelphia; but, tired of waiting and anxious to carry out experiments which should solve all doubts, he had recourse to a more expeditious instrument, and one, as events proved, not less efficacious, for getting into touch with the region of thunder--a kite such as children play with.

He prepared two sticks in the form of a cross, with a silk handkerchief stretched upon them, and with a string attached of suitable length, and set forth on his mission the first time there was a storm. He was accompanied only by his son. Fearing the ridicule that is showered upon failure, he did not take any one else into his confidence. The kite was set flying. A cloud which looked promising pa.s.sed without result. Others followed, and the excitement with which they were awaited can be imagined.

At first there was no spark and no sign of electricity. Presently some filaments of the string began to move, as though they had been pushed out, and a slight rustling could be heard. Franklin now touched the end of the string with his finger, and instantly a spark was given out, followed quickly by others. Thus for the first time the genius of man may be said to have come to grips with lightning, and begun to learn the secret of its existence.

This experiment took place in June, 1752, and made an immense sensation throughout the world, and was repeated in other countries, always with the same success.

A French magistrate, named de Romas, making use of Franklin's idea as soon as it was known in France, took it into his head to use a kite with raised cross-bars, and in June, 1753, before the full results of Franklin's experiments were made public, secured still more remarkable signs of electricity, having inserted a thread of metal throughout the whole length of the string, which was 260 metres. Later, in 1757, de Romas repeating his experiments during a storm, secured sparks of a surprising size. "Imagine before you," he said, "lances of fire nine or ten feet in length and an inch thick, and making as much noise as pistol shots. In less than an hour I had certainly thirty lances of this length, without reckoning a thousand shorter ones of seven feet and under." Numbers of people, ladies among them, were present at these experiments. They were not without danger, as may be imagined; de Romas was once knocked over by an unusually heavy discharge, but without being seriously hurt.

Franklin was the first to turn his experiments to practical account, attaching lightning-conductors to public and private buildings for their protection, and achieving marvellous results; the lightning being caught by the metallic stem and following it obediently into the ground.

From this time, lightning-conductors came into almost universal use, and their value was not long in being generally recognized. Curiously enough, France, which had been ahead of all other countries in the study of electricity, was not one of the earliest to go in for lightning-conductors. There were, indeed, signs of strong hostility to their introduction. It was held even that they went against the designs of Providence. In 1766, the Abbe Poncelet, in his work ent.i.tled "La Nature dans la formation du tonnerre et la reproduction des etres vivants," in which he sets out to demonstrate that the force which produces lightning is the same as that which causes the earth to fructify, makes a strong protest against the construction of lightning-conductors.

In 1782, nevertheless, at the reiterated request of Le Roi, a member of the Academie des Sciences, and friend and admirer of Franklin, the Louvre was endowed with the first lightning-conductor put up on a public building in France. Soon afterwards they became common.

In 1784 the Academie des Sciences drew up the first set of rules for the construction of lightning-conductors. It was revised and corrected in 1823, in accordance with the various improvements that had been introduced up till then, and it has been further added to in 1854, 1867, and 1903. These instructions point out that the most important metallic portions of the building should be placed in communication with the conductor, and this should sink into a well. Conductors that are not perfectly constructed are a source of danger, instead of being a protection, for the electric current is apt, instead of running down into the earth, to make for any kind of metallic substance, and cause great havoc.

The conductor ought really to communicate with a large body of water--a body of water of greater extent than the storm cloud from which the lightning comes. When the flow is insufficient, the water itself is apt to become electrically charged. It is dangerous to bury the conductor in merely damp soil; first, because one generally does not know whether there is enough of this soil; secondly, because one cannot be sure that the humidity will be sufficient at times of great drought--the very times when storms are most to be feared. Failing a river or great pond, the conductor should be put into wells issuing or having their source in inexhaustible supplies of water deep down in the soil.

In his table of statistics showing the number of cases in which lightning has struck either lightning-conductors, or buildings, or ships furnished with conductors, Quebelet gives a hundred and sixty-eight cases in which the conductor has been struck, and in only twenty-seven instances of these (one-sixth of the whole) have the conductors, from some grave flaw in their construction, failed to fulfil their office. These results are the best proof possible of the efficacy of conductors, and the best answer to those who decry them.

The area of protection covered by the conductor is not so great as is generally supposed. It is limited to a distance about three or four times the length of the conductor above the roof. Thus a conductor standing out five yards will protect an area stretching only about fifteen or twenty yards away. This depends also to some extent upon the nature of the place and the materials of which the house is constructed.

Buildings are often struck by lightning because the number of conductors has been insufficient for the extent of the edifice to be protected.

To remedy this defect, conductors are made with a number of separate stems--veritable wire traps in which to catch the lightning. This system, the invention of a Belgian physicist, M. Melsens, decreases considerably the risks of destruction, and is much more economical than the erection of a number of separate conductors.

A conductor of this kind has been installed on the Hotel de Ville at Brussels, which has been well protected from lightning ever since, whereas previously this building had been struck by lightning several times in spite of the single conductors with which it was supplied.

The metallic trellis is in communication with the sewers.

The slaughter-houses of La Villette, the Hotel Evigne, and other buildings in Paris, are provided with similar defences.

The Eiffel Tower boasts several such multiplex conductors. It has often been struck by lightning, but no one who has happened to be up it at the time has ever suffered any damage therefrom. The lightning strikes the conductor sometimes from out the actual cloud--curious photographs have been taken of this. The Eiffel Tower is in itself a gigantic lightning-conductor.