Charles-François de Changy

"It was Professor Jobard, of Brussels, who gave the first impulse to the highly important experiments with glow lamps. This savant suggested, in the year 1838, in the Courrier Libéral, that a small strip of carbon in a vacuum used as a conductor of a current, would emit an intense, fixed, and durable light. Prof. Jobard then advised his former pupil, De Changy, to attempt the practical realisation of his idea. De Changy was the more ready to enter upon the necessary experiments as he, in his capacity of mining engineer, considered he would be able to open up a wide field for glow light illumination in the shafts and galleries of mines.

"After some preparatory theoretical study De Changy commenced his labours in the year 1844, after an Englishman, of the name of Moleyns, had, as early as 1841, made the first experiment with platinum glow light lamps. De Changy made use of gas carbon cut into thin strips, which he enclosed in an exhausted glass and connected with the conducting wires. In order to impart more consistency to the carbon strips he attempted to fill up their pores by soaking them in melted rosin or in sugared solutions. The result obtained was relatively favourable, and De Changy proceeded to the construction of the first carbon glow lamp. This was, however, the first link of that chain of experiments which runs like a red thread through the history of the development of the glow lamp. The experiments failed, on the one hand, by the carbon strips becoming disintegrated by the current, and, on the other hand, because the electric energy required for the production of the light was too great, and the degree of heat generated in the carbons too intense. The lamp was also imperfectly sealed and the vacuum insufficient, in consequence of which circumstance the carbon partially consumed away in the oxygen of the air... Shortly after this rather encouraging experience De Changy received the appointment of engineer-in-chief to the Weal-Ocean and Weal-Ramoth mines, in consequence of which his interesting studies and experiments were interrupted for a long period.

"...Ten years after King had patented his lamp, in the year 1855, De Changy resumed his experiments and studies with redoubled zeal. He made experiments at the same time in two directions. Without altogether abandoning carbon, he occupied himself with the construction of a glow lamp, in which platinum formed the conductor, as he imagined to attain by the use of that metal a success more speedy, although less perfect, yet of sufficiently practical value. Being well aware that in order to guard the platinum wire against the risk of fusing, the strength of the electric current must strictly be kept within certain limits, he constructed a current regulator which he patented in 1858.

"The lamps provided with such a regulator would be used for various interesting purposes, as, for instance, for the illumination of mines, submerged for fishing purposes, for illuminating anchor buoys, and, finally, as a nautical telegraph by which, with the aid of an instrument like a keyboard, signals consisting of flashes of light could be transmitted from the top of the mast of a vessel. The platinum for these lamps was submitted to a peculiar process of preparation. De Changy caused the metal to be maintained some time heated to a moderate degree of redness, and then gradually raised it to that degree of heat to which it would be required to be heated for illuminating purposes.

"The reader of this pamphlet will perhaps be interested to learn to what extent industrial matters were at that time tabooed by the Academy of Sciences of Brussels, and how narrow-minded and biased an opinion was entertained in scientific circles of those who tilled the field of scientific research for practical purposes. When De Changy, a short time before he obtained his patent, submitted the result of his experiments to the Academy, that body appointed a committee for the purpose of subjecting his invention to a crucial test.

"Deprez, a member of that committee, requested Professor Jobard by letter to furnish a detailed description of the apparatus relating to De Changy's invention, together with a full account of the technical proceedings. M. Jobard was, of course, compelled to answer that he could not possibly comply with that request, as the publication of the information required might be detrimental to the patent applied for. Deprez then declared, in reply, that as De Changy intended to convert his invention into a lucrative business he did not deserve to be called a savant, and that the Academy could not for that reason further occupy itself with his invention.

"This answer was, of course, not calculated to encourage De Changy in the pursuance of his researches; and so it came to pass that he shortly afterwards abandoned his experiments with carbon glow lamps."

It was mentioned that de Changy became involved with the incandescent lamp in 1844. It would appear from a brief note in Nature¹ that he was involved again in the year 1882 - 38 years later.

In regard to the matter with the "Academy of Sciences of Brussels", Park Benjamin stated⁵ that it was the French Academy of Sciences and that 'De Changy claimed to have succeeded at this time in arranging several lamps in one circuit, which could be lighted simultaneously in groups, or separately without affecting the normal intensity of each.' In their book³ Alglave and Boulard said:

"The invention of M. de Changy made a great noise at once; but the noise soon ceased in presence of the undeniable inconveniences, which made the system almost impossible in practice. The principal one of these inconveniences is the ease with which platinum melts if the temperature at which it furnishes a good white light be exceeded. A slight variation in the intensity of the electric current is sufficient to produce this injurious heating, and as yet they were unable to regulate, even in an approximate manner, the force of the current employed.

"Mr. Jobard, director of the Industrial Museum at Brussels, cited no precedent in announcing on February 27, 1858, to the Academy of Sciences at Paris, that M. de Changy had succeeded in resolving the problem of the divisibility of the electric light."

Apparently comments of de Changy appeared in an article⁷ in La Lumière Electrique in which he mentioned some of the work he and another scientist had done as far back in time as 1838. The picture below is an artist's conception of de Changy showing an incandescent lamp in the mine gallery; the picture was scanned from Fig. 36 of Figuier's book²

Jobard apparently had great interest in the lighting of mines because he invented an economical oil lamp. The lamp was called a "lamp for the poor" or "lamp for one"¹⁰. It was designed as a light source for just one person. He published at least ten articles in the scientific literature from 1835 - 1858⁹.

"C. De Changy was Charles-Francois De Changy, being born on July 22, 1817 in the city of Saint-Avertin, which is in the department of Indre-et-Loire, France. The city of Saint-Avertin is located a few kilometers to the south of the city of Tours, the capital of the department of Indre-et-Loire. De Changy was described as an engineer (ingénieur).

"Apparently De Changy lived in Brussels as early as 1851, residing at 9 Rue de l'Etoile. From at least the year 1856 to 1865 he lived at No. 191 Rue Terre-Neuve, in Brussels, with his mother, who was born in the city of Tours. On January 11, 1865 he married Jeanne-Joséphine Dedeyn, a hat maker, who was born on July 17, 1843."

' "In some of the early experiments of Sir Humphrey Davy we find mention of the heating to luminosity of wires of various metals, as tests of the comparative power of different batteries; and, in 1858, so great an advance had been made in the practical utilization of this means of lighting, that M. Jobart, in a report to the Academy of Sciences, in Paris, was able to speak as follows:

" ' "I hasten to announce to the Academy the important discovery of the dividing of an electric current for lighting purposes. This current, from a single source, traverses as many wires as may be desired, and gives a series of lights ranging from a night lamp to a light house lamp.

" ' "The luminous arc between the carbons produces, as is well known, a very intense, flickering, and costly light. M. de Changy, who is a chemist, mechanician, and physicist, is thoroughly conversant with the latest discoveries, and has just solved the problem of dividing the electric light.

" ' "In his laboratory, where he has worked alone for the past six years, I saw a battery of twelve Bunsen elements producing a constant luminous arc between two carbons, in a regulator of his own invention - this regulator being the most simple and perfect I have ever seen. A dozen small miner's lamps were also in the circuit, and he could, at pleasure, light or extinguish either one or the other, or all together, without diminishing or increasing the intensity of the light through the extinction of the neighboring lamps. The lamps, which are closed in hermetically sealed glass tubes, are intended for the lighting of mines in which there is fire damp, and for the street lamps, which would by this system be all lighted or put out at the same time, on the circuits being opened or closed. The light is as white and pure as Gillard's gas, with which it has one point in common, namely, its production by the incandescence of platinum. The gas-pipes are replaced by simple wires, and no explosions, bad smells, or fires can take place.

" ' "The trials that have been hitherto made, with the object of producing an electric light by means of heated platinum, have failed on account of the melting of the wires. This difficulty has been overcome by M. de Changy's dividing regulator. The cost of the light is estimated to be half that of gas. A lamp placed at the masthead of a ship would form a permanent signal for about six months, without the necessity of changing the platinum. With several such lights, placed in tubes of colored glass, it would be easy to telegraph by night, as they could be extinguished and relighted rapidly from the deck.

" ' "For light-house purposes considerable amplitude can be given the light. I also saw a lamp so arranged in a thick glass globe that it could be immersed to considerable depths without being extinguished by any movement. This lamp has already been used in the taking of fish which were attracted toward the light.

" ' "The above slight description will suffice to show to what variety of applications this discovery can be put. The communication which I have had the honor of laying before the Academy is founded upon no illusion; a lamp was, to my astonishment, lit in the hollow of my hand and remained alight after I had put it in my pocket with my handkerchief over it." ' "

' "In Comptes Rendus, or minutes of the French Academy, I find that the communication of M. Jobart was received at the meeting held March 1, 1858, and was referred to M. Becquerel. At a meeting of April 5, M. Becquerel reported that he did not find anything sufficiently definite to warrant the Academy to express an opinion as to the importance of this discovery..." '