ePub 版

was, as usual, of hemp, except the lower end, which was silk.

Where the hempen string terminated, a key was fastened. With this apparatus, on the appearance of a thunder-gust approaching, he went into the commons, accompanied by his son, to whom along he communicated his intentions, well knowing the ridicule which, too generally for the interest of science, awaits unsuccessful experiments in philosophy. He placed himself under a shed to avoid the rain. His kite was raised. A thunder cloud passed over it. No signs of electricity appeared. He almost despaired of success ; when suddenly he observed the loose fibres of his string to move towards an erect position. He now presented his knuckle to the key, and received a strong spark. How exquisite must his sensations have been at this moment! On this experiment depended the fate of his theory. If he succeeded, his name would rank high amongst those who have improved science ; if he failed, he must inevitably be subjected to the derision of mankind, or, what is worse, their pity, as a well-meaning man, but a weak, silly projector. The anxiety with which he looked for the result of his experiment, may easily be conceived. Doubts and despair had begun to prevail, when the fact was ascertained in so clear a manner, that even the most incredulous could no longer withhold their assent.Repeated sparks were drawn from the key, a phial was charged, a shock given, and all the experiments made, which are usually performed with electricity,

About a month before this period, some ingenious Frenchmen had completed the discovery, in the manner originally proposed by Dr. Franklin. The letters which he sent to Mr. Collinson, it is said, were refu. sed a place amongst the papers of the Royal Society of London. However this may be, Collinson published them in a separate volume, under the title of New Experiments and Observations on Electricity, made at Philadelphia, in America. They were read with avid. ity, and soon translated into different languages. A very incorrect French translation fell into the hands of the celebrated Buffon, who notwithstanding the disadvantages under which the work labored, was much pleased with it, and repeated the experiments with success. He prevailed upon his friend, M. D'Alibard, to give his countrymen a more correct translation of the work of the American electrician. This contributed much towards spreading a knowledge of Franklin's principles in France. The King, Louis XV. hearing of these experiments, expressed a wish to be a spectator of them. A course of experiments was given at the seat of the Duc D'Aven, at St. Germain, by M. De Lor. The applauses which the king bestowed upon Franklin, excited in Buffon, D’Alibard, and De Lor, an earnest desire of ascertaining the truth of his theory of thunder-gusts. Buffon erected his apparatus on the tower of Montbar. M. D'Alibard at Maryla-ville, and De Lor at his house in the Estrepade at Paris, some of the highest ground in that capital. D’Alibard's machine first shewed signs of electricity. On the 10th of May, 1752, á thunder-cloud passed over it, in the absence of M. D’Alibard, and a number of sparks were drawn from it by Coiffier, a joiner, with whom D'Alibard had left directions how to proceed, and by M. Raulet, the prior of Mary-la-ville. An account of this experiment was given to the Royal Academy of Sciences, in à memoir by M. D'Alibard, dated May 13th, 1752. On the 13th of May, M. De Lor proved equally successful with the apparatus erected at his own house. These discoveries soon excited the philosophers of other parts of Europe to repeat the experiment. Amongst these, none signalized themselves more than Father Becaria of Turin, to whose observations science is much indebted. Even the cold regions of Russia were penetrated by the ardor for discovery. Professor Richman bade fair to add much to the stock of knowledge on this subjecta when an unfortunate flash from his rod put a period to his existence. The friends of science will long remember with regret the admirable martyr to electricity.

By these experiments Franklin's theory was established in the most firm manner. When the truth of it could no longer be doubted, the vanity of men endeavored to detract from its merit. That an American, an inhabitant of the obscure city of Philadelphia, the name of which was hardly known, should be able to make discoveries, and to frame theories, which had escaped the notice of the enlightened philosophers of Europe: was loo mortifying to be admitted. He must certainly have taken the idea from somebody else. An American, a being of inferior order, make discoveries! Impossible. It was said, that the Abbe Nollet, in 1748, had suggested the idea of the similarity of lightning and electricity, in his Lecons de Phisique.It is true, that the Abbe mentions the idea, but he throws it out as a bare conjecture, and proposes no mode of ascertaining the truth of it. He himself acknowledges, that Franklin first entertained the bold thought of bringing lightning from the heavens, by means of pointed rods fixed in the air. The similarity of electricity and lightning is so strong, that we need not be surprised at notice being taken of it, as soon as electrical phenomena became familiar. We find it mentioned by Dr. Wall and Mr. Gray, while the science was in its infancy. But the honor of forming a regular theory of thunder-gusts, of suggesting a mode of determining the truth of it by experiments, and of putting these experiments in practice, and thus establishing his theory upon a firm and solid basis, is incontestibly due to Franklin. D’Alibardı. who made the experiments in France, says, that he only followed the track which Franklin had pointed out.

It has been of late asserted, that the honor of completing the experiment with the electrical kite, does

not belong to Franklin. Some late English paragraphs have attributed it to some Frenchman, whose name they do not mention ; and the Albe Bertholon gives it to M. De Romans, assessor to the presideal of Nerac.; the English paragraphs probably refer to the same person. But a very slight attention will convince us of the injustice of this procedure ; Dr. Franklin's experiment was made in June 1752 ; and his leta ter, giving an account of it, is dated October 19, 1752, M. De Romas made his first attempt on the 14th of May 1753, but was not successful until the 7th of June ; a year after Franklin had completed the discovery, and when it was known to all the philosophers in Europe.

Besides these great principles, Franklin's letters on electricity contain a number of facts and hints, which have contributed greatly towards reducing this branch of knowledge to a science. His friend, Mr. Kinnersly, communicated to him a discovery of the different kinds of electricity excited by rubbing glass and sulphur. This, we have said, was first observed by M. Du Faye ; but it was for many years neglected. The philosophers were disposed to account for the phenomena, rather from a difference in the quantity of electricity collected ; and even Du Faye himself seems at last to have adopted this doctrine. Franklin at first entertained the same idea; but upon repeating the experiments, he perceived that Mr. Kinnersley was right; and that the vitreous and resinous electricity of Du Faye were nothing more than the positive and neg. ative states which he had before observed ; that the glass globe charged positively, or increased the quantity of electricity on the prime conductor ; whilst the globe of sulphur diminished its natural quantity, or charged negatively. These experiments and observations opened a new field for investigation, upon which electricians entered with avidity; and their la." yours have added much to the stock of our knowledge

[ocr errors]

In September, 1752, Franklin entered upon a course of experiments, to determine the state of electriciiy in the clouds. From a number of experiments le formed this conclusion : “ that the clouds of a thunder. gust are most commonly in a negative state ci cieciricity, but sometimes in a positive state ;” and liom this it follows, as a necessary consequence, “that, for the most part, in thunder-strokes, it is the earth that strikes into the clouds, and not the clouds that sirike into the earth.” The letter containing these observaç tions is dated in September, 1753 ; and yet the discove ery of ascending thunder has been said io te of a mod, orn date, and has been attributed to the Abbe Barthom ion, who published his memoir on the subject in 1776.

Franklin's letters have been translated into most of the European languages, and into Latin. In propore tion as they have become known, his principles biave been adopted. Some opposition was made to his theories, particularly by the Abbe Nollet, who was, however, but feebly supported ; whilst the first philosophers of Europe stepped forth in defence of FrankJin's principles ; among whom D'Alibard and Beccaria were the most distinguished. The opposition has gradually ceased, and the Franklinian system is now universally adopted, where science flourishes.

The important practical use which Franklin-made of his discoveries, the securing of houses from injury by lightning, has been already mentioned. Pointed conductors are now very common in America; but prejudice has hitherto prevented their general introduction into Europe, notwithstanding the most un. doubled proofs of their utility have been given. But mankind can with difficulty be brought to lay aside established practices, or to adopt new ones. And perhaps we have more reason to be surprised that a practice, however rational, which was proposed about forty years ago should in that time have been adopted in so many places, than that it has not universally pre

« 上一頁繼續 »