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 noble character, and his devotion to his country, has won the admiration and gratitude 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 ambassador, and finally President of the Assembly 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 glass, 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 passed 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 AbbÉ Poncelet, in his work entitled "La Nature dans la formation du tonnerre et la reproduction des Êtres 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 HÔtel EvignÉ, 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.

Portable conductors have been invented from time to time—silk umbrellas without iron ribs, and clothes of indiarubber and such-like; but they have all been childish things.

Without allowing one's self to get lightning, so to speak, on the brain, it is well to take certain precautions during a storm.

The first and principal one is not to get under a tree.

The second is to give a wide berth to telegraph posts, so as to avoid contact with the sparks that may issue from them.

Movements of the air having the effect of preparing an excellent route for the fluid, it is well not to run in a storm. It is well also not to ring a bell.

It is well, also, to avoid being in the neighbourhood of animals, in view of their attraction for lightning.

In houses, doors and windows should be closed in order to avoid draughts. It is well to keep away from the chimney, too, as well as from metallic objects.

But lightning always has its caprices. It is this that makes its study so interesting.