Very silently, in the dark of night, the priests of the Siena cathedral, directed by Abbé Toaldo, laid their iron rods along the walls of the building, but inside, planting them deep into the ground, and with the pointed summit only a few feet above the highest point of the steeple, so as to be scarcely perceptible from below by the naked eye. Still the secret of what had been done could not be entirely kept from the multitude. Some of the workmen, engaged in the operation of fixing the iron rods to the inner walls and steeple of the cathedral, whispered about what they had been doing, trembling at the evil consequences of their work, notwithstanding having received full absolution from their employers. Murmurs were now heard everywhere, and there were signs of a popular outbreak, just when one of the many thunderstorms regularly visiting the mountain city crept over it on April 18, 1777. Portentously the black clouds laid themselves thicker and thicker over the high cathedral, till all the people of Siena crept forth from their houses, awaiting in breathless expectation the terrors to come. Then the dark masses discharged their fiery streams; flash followed flash, till one, a long hissing tongue of flame, fell down upon the cathedral steeple, distinctly visible to thousands of beholders. A few minutes after, a ray of sunshine pierced the dark clouds, and to the bewildering astonishment of the masses, the cathedral was standing there absolutely unhurt. As if to exhibit its wonderful power, the gilded point of the lightning conductor stood out brilliantly in the sun, pointing in radiant silence up to heaven. ‘Maraviglia, maraviglia!’ cried people and priests in chorus. High mass was held forthwith in the wonderfully preserved cathedral, and on the same day the magistrates of Siena went into the town hall and had a record made in the book containing the annals of the city, to make known to all posterity that their noble cathedral had just been preserved from destruction by the astounding influence of an ‘heretical rod.’ Though not in the least intended to be sarcastic, the irony could not have been more complete.
There was a most remarkable historical concurrence between the gradual introduction of lightning conductors into Europe and that of the art of vaccination. Both the great scientific discoveries had the same end in view for the benefit of mankind, the one teaching the art of drawing the dangerous electric fire of the clouds harmlessly into the earth, and the other that of extracting the poisonous seed of disease from the human body. Both were brought forward with the noblest intentions; and both encountered the most violent opposition from religious fanatics, the same in substance, as interfering with the decrees of Providence, and the ordained wrath of heaven. Both triumphed in the end, and almost exactly at the same time, though the battle of the great medical discovery lasted longer, and was more fiercely fought than that of Franklin’s invention. To make the analogy between the progress of lightning conductors and of vaccination complete, it so happened that in at least one conspicuous instance the same man was an important agent in forwarding the success of both discoveries. The person in question was Dr. Johan Ingenhousz, a native of Breda, in the Netherlands, born in 1730. A man of great natural gifts, he came to England when about thirty years of age, practising as a physician, and attending specially to the so-called Suttonian method of inoculation against the small-pox, then an entirely new branch of medical science. At the same time he eagerly embarked in electrical experiments, got into correspondence with Benjamin Franklin, and, having made many friends, was elected a fellow of the Royal Society in 1769. Recommended to the king, Dr. Ingenhousz became a favourite at court, owing chiefly to his perfect knowledge of German, which resulted in his being recommended to a highly profitable as well as distinguished mission. The famous Imperial lady, the Elizabeth of her age, Maria Theresa of Austria, had read of the benefits of vaccination, then chiefly known in England, and wishing to confer them on her own family and friends, she asked King George the Third to recommend to her some able physician, who could come to Vienna for the purpose. His Majesty at once named Dr. Johan Ingenhousz, a recommendation warmly supported by the President of the Royal Society, Sir John Pringle, who had taken an affection for the young Dutch physician on account of his electrical researches, which had resulted in the invention of a novel apparatus, subsequently known as the plate electrical machine.
Dr. Ingenhousz set out for Vienna in 1772, was received with marked honours by the great Empress, and having done his work, and wishing to visit Italy, received an autograph letter of Maria Theresa to her son, Grand Duke Leopold of Tuscany. At the court of this enlightened prince, Dr. Ingenhousz resided for some time, practising vaccination, but also engaged in electrical experiments, which created the greatest interest. It was partly by his advice that the Grand Duke consented, in the teeth of desperate priestly opposition, to erect one of Franklin’s lightning conductors over his own palace, and to set them up likewise for the protection of all the powder magazines in Tuscany. This done, Dr. Ingenhousz went forward to Padua, invited by some of the professors of the university, and by the famous senator of Venice, Angelo Querini, who had a magnificent palace in the neighbourhood of the city. In this palace, bearing the name of Altichiera, the ‘English doctor,’ as he was called, was made to reside, practising vaccination, the same as at the court of Florence, but following as a favourite occupation the setting-up of ‘heretical rods.’ Altichiera itself had the first erected in May 1774, and soon after Dr. Ingenhousz had the satisfaction of planting another over the astronomical observatory of the university of Padua, in the presence of an enormous crowd of students who lustily applauded, and of an angry multitude, kept in the background less by persuasion than the strong arms of the young men. As at Siena, so at Padua, the mob became pacified not long after by seeing the lightning fall upon the observatory, much exposed by its situation, and which had often been struck before, without doing the least damage. From Padua, Dr. Ingenhousz went to Venice, in company of his friend and patron, Senator Angelo Querini. Here his efforts to spread the knowledge of lightning conductors, together with vaccination, had the best results. The church of St. Mark and other public buildings were surmounted before long by the awe-striking ‘heretical rods,’ and on May 9, 1778, the Senate of Venice issued a decree ordering the erection of lightning conductors throughout the republic. It was the first recognition of the value of conductors by any government of Europe, or, indeed, of the world.
CHAPTER V.
METALS AS CONDUCTORS OF ELECTRICITY.
In the history of human inventions and discoveries, the idea of the lightning conductor is almost the sole one which sprang, all but perfect, from one brain, like Minerva, in Greek mythology, from Jupiter’s head. Benjamin Franklin discovered the lightning conductor, and, except some important improvements in its manufacture, due to the progress of the metallurgical arts, the conductor remains the same, in essence, as designed by the world-famous citizen of Philadelphia. The reason of this is plain enough. Though one of the most brilliant discoveries in the annals of mankind, the lightning conductor, by itself, is one of the simplest of things. Franklin found by experiments, that the mysterious so-called ‘electric fluid’ had a tendency to make its way in preference through metals, and so he recommended the laying-down of a metallic line from the clouds to the earth to prevent damage to surrounding objects, such as buildings and the human beings within them. More than this he did not know; and more than this we, to this day, do not know. Of the inner nature, or constitution, of that grand cosmic discharge of electricity to which the name of lightning is given, no scientific explanation can be given. We are utterly ignorant of it, and in all probability ever will be.
But while the general principle laid down by Franklin, that metals will conduct the electric force harmlessly from the clouds to the earth, remains the same, very much has been learnt, in the progress of scientific investigation, as regards the varying conducting capacity of different metals. The first conductors were invariably rods of iron, this metal being preferred by Franklin and his immediate followers as cheap, ready at hand, and answering all purposes in practice. But it was gradually found by experiments that there are other metals through which the electric force will make its way more rapidly than through iron. One of the earliest investigators of this subject was Sir Humphrey Davy, the celebrated inventor of the miner’s safety lamp. It was while studying the decomposition of the fixed alkalies by galvanism, and tracing the metallic nature of their bases, to which he gave the names of sodium and potassium, that the great chemist and natural philosopher was brought to enter upon an examination of what may be called the permeability of the different metals by the electric force. The result of his investigations, as stated by him, was that silver stood highest as a conductor of electricity; next to it coming copper; then gold; next, lead; then platinum; then the new metal called palladium—discovered by Wollaston, 1803, in platinum—and lastly, iron. These were the principal metals experimented upon by Sir Humphrey Davy, and the net result of his inquiries was expressed summarily in the fact of copper being more than six times, and silver more than seven times, as good a conductor as iron. Taking copper at 100, Sir Humphrey Davy drew up the following table of the electrical conductivity of the seven metals:—
| Silver | 109·10 |
| Copper | 100·00 |
| Gold | 72·70 |
| Lead | 69·10 |
| Platinum | 18·20 |
| Palladium | 16·40 |
| Iron | 14·60 |
The practical result of these experiments was that it came to be recognised that, among the metals, copper might be employed to greater advantage as a lightning conductor than iron: a much lesser substance of it doing the same service of passing a given quantity of electricity from the clouds harmlessly into the earth.