THE FIRST EXPERIMENTS WITH THE ELECTRIC LIGHT.
Electric lighting dates back, as well known; to the celebrated experiment of Sir Humphry Davy, which took place in 1809 or 1810, but the date of which is often given as 1813. There exist however, some indications that experiments on the production of the electric spark between carbons had been performed before the above named date.
Mr. S.P. Thompson has given the following interesting details in regard to this subject: In looking over an old volume of the Journal de Paris, says he, I found under date of the 22d Ventose, year X. (March 12, 1802), the following passage, which evidently refers to an exhibition of the electric arc:
"Citizen Robertson, the inventor of the phantasmagoria (magic lantern), is at present performing some interesting experiments that must doubtless advance our knowledge concerning galvanism. He has just mounted metallic piles to the number of 2,500 zinc plates and as many of rosette copper. We shall forthwith speak of his results, as well as of a new experiment that he performed yesterday with two glowing carbons.
SIR HUMPHRY DAVY'S ELECTRIC LIGHT EXPERIMENTS IN 1813.
"The first having been placed at the base of a column of 120 zinc and silver elements, and the second communicating with the apex of the pile, they gave at the moment they were united a brilliant spark of an extreme whiteness that was seen by the entire society. Citizen Robertson will repeat this experiment on the 25th."
The date generally given for the invention of the electric light by Sir Humphry Davy is 1809, but previous mentions of his experiment are found in Cuthberson's "Electricity" (1807) and in other works. In the Philosophical Magazine, vol. ix., p. 219, under date of Feb. 1, 1801, in a memoir by Mr. H. Moyes, of Edinburgh, relative to experiments made with the pile, we find the following passage:
"When the column in question had reached the height of its power, its sparks were seen by daylight, even when they were made to jump with a piece of carbon held in the hand."
ELECTRIC LIGHTING IN PARIS IN 1844.
In the Journal of the Royal Institution, vol. i. (1802), Davy describes (p. 106) a few experiments made with the pile, and says:
"When, instead of metals, pieces of well calcined carbon were employed, the spark was still larger and of a clear white."
On page 214 he describes and figures an apparatus for taking the galvano-electric spark into fluid and aeriform substances. This apparatus consisted of a glass tube open at the top, and having at the side a tube through which passed a wire that terminated in a carbon. Another wire, likewise terminating in carbon, traversed the bottom and was cemented in a vertical position.
But all these indications are posterior to a letter printed in Nicholson's Journal, in October, 1800, p. 150, and entitled: "Additional Experiments on Galvanic Electricity in a Letter to Mr. Nicholson." The letter is dated Dowry Square, Hotwells, September 22, 1800, and is signed by Humphry Davy, who at this epoch was assistant to Dr. Beddoes at the Philosophical Institution of Bristol. It begins thus:
"Sir: The first experimenters in animal electricity remarked the property that well calcined carbon has of conducting ordinary galvanic action. I have found that this substance possesses the same properties as metallic bodies for the production of the spark, when it is used for establishing a communication between the extremities of Signor Volta's pile."
In none of these extracts, however, do we find anything that has reference to the properties of the arc as a continuous, luminous spark. It was in his subsequent researches that Davy made known its properties. It will be seen, however, that the electric light had attracted attention before its special property of continuity had been observed.
It results from these facts that Robertson's experiment was in no wise anterior to that of Davy. The inventor of the phantasmagoria did not obtain the arc, properly so called, with its characteristic continuity, but merely produced a spark between two carbons--an experiment that had already been made known by Davy in 1800. The latter had then at his disposal nothing but a relatively weak pile, and it is very natural that, under such circumstances, he produced a spark without observing its properties as a light producer.
It was only in 1808 that he was in a position to operate upon a larger scale. At this epoch a group of men who were interested in the progress of science subscribed the necessary funds for the construction of a large battery designed for the laboratory of the Royal Institution. This pile was composed of 2,000 elements mounted in two hundred porcelain troughs, one of which is still to be seen at the Royal Institution. The zinc plates of these elements were each of them 32 inches square, and formed altogether a surface of 80 square meters. It was with this powerful battery that Davy, in 1810, performed the experiment on the voltaic arc before the members of the Royal Institution.
The carbons employed were rods of charcoal, and were rapidly used up in burning in the air. So in order to give longer duration to his experiment, Davy was obliged, on repeating it, to inclose the carbons in a glass globe like that used in the apparatus called the electric egg. The accompanying figure represents the experiment made under this form in the great ampitheater of the Royal Institution at London.--La Lumiere Electrique.