Eugene Edouard DEsirE Branly was French physicist, inventor of wireless telegraphy. Although, his name little known abroad, Branly is considered in France as a symbol of the alliance of science and technology.
Young Eugene Edouard Branly
Eugene Edouard DEsirE Branly was born in Amiens, France, on October 23, 1844, in a profoundly catholic middle class family. His father, Joseph Edouard Branly (b. 1816), was a teacher in a high school. His mother was Elise Emilie nee Gillion (b. 1814). In March 1845 the family moved to Saint Quentin where the father received some promotion in the ImperialSecondary school.
Eugene Edouard Branly received classical education passing all stapes of schooling with a lot of success. He always preferred natural science, whereas his father wished him to study more humanitarian sciences. In 1862 young Eugene Edouard Branly left Saint-Quentin where he received his early education at the LycEe of St. Quentin and went to Paris to continue his education in the imperial Secondary school Napoleon (now LycEe Henri IV) in a special class of mathematics.
He finished the first year with average grades being 12th from 34 pupils. Then in 1864 Branly tried to enter a polytechnic college but he was not successful. In 1865 he entered the Ecole Normale Superieure where he successfully studied physics. In 1868 he became Licentiate (teaching position) in mathematics and physical science, and also agrEgE (post on the teaching staff) in physical and natural science.
In summer of 1868 Branly started his career as a professor at the LycEe of Bourges, but after a few months, in 1869, he returned to Paris where he received a position of a leader (chef des travaux) of a Physics Laboratory in Sorbonne and four years later he was made director of the Laboratory of Instruction in the Departrnent of physics at the Sorbonne. In the same year (1873) he won the doctorate in science with a thesis entitled “Electrostatic phenomena in Voltaic Cells”.
On February 5th, 1874, he became a deputy director of M. Desaint’s laboratory, what allowed him to double his salary. During all this period, he complained that his laboratory was not well equipped, however, he didn’t receive enough finance for his research. This was the reason for him to leave Sorbonne.
He had one more personal reason to quit – he was not happy with the suggested marriage with his boss’ daughter that resulted in some personal problems. He resigned his post at the Sorbonne on December 15th, 1875, to become professor of physics at the Catholic University in Paris on January 19th, 1876. This was a newly organized University with a well equipped physical laboratory that made him especially happy.
Branly then took up the study of medicine, obtaining his degree in medicine in 1882 with the thesis: “Study of hemoglobine in blood by optical means” (“Dosage de l’hEmoglobine dans le sang par les procEdEs d’optiques”.) Thereafter Branly divided his time between the practice of medicine, especially of physiotherapy and electrotherapy, and his researches in physics at the Catholic University.
In the morning, he would go to the SalpÃªtriere or Hotel-Dieu hospitals in Paris, where he subjected patients’ bodies to electric shocks, luminous discharges and induced currents. In the afternoon, it was the turn of metallic conductors and galvanometers to be charged with electricity in his physics laboratory.
Dr. Branly is best known by his researches concerning radio-conductors, and particularly by his so-called “coherer”. He began his studies in this field in 1890, being led to undertake them by observing the anomalous change in the resistance of thin metallic films when exposed to electric sparks. Platinum deposited upon glass was first employed. The effect was at first attributed to the influence of the ultraviolet light of the spark. The variations in the resistance of metals in a finely divided state were even more striking, and they were shown by Dr. Branly to be due to the action of the electrical, or Hertzain, waves of which the spark was the source. The further experiment led to the coherer, which is simply a glass or ebonite tube containing metallic filings which connect the two ends of a wire conductor entering the tube.
When the tube is made part of a battery circuit, the filings ordinarily offer a very great resistance to the passage of a current. But if a spark be produced in the neighbourhood between the terminals of an induction coil, or by the discharge of a Leyden Jar, the resistance of the filings is diminished, being no longer measured in millions but in hundreds of ohms. Upon tapping the tube the filings regain their normal resistance.
Branly in his lab with his assistants
At that time, although the action of the spark on the tube could be observed across the walls of his laboratory and over a distance of up to twenty metres, Branly never dreamed of the possibility of transmitting signals by this means. He was mainly concerned with establishing a parallel between medicine and physics, and was to offer the medical world an interpretation of nerve conductivity based on the model of the conductivity of filings tubes.
The “coherer” took radio transmission out of the laboratory and made communication over long distances possible. Later this simple device was employed by Lodge in his researches and formed an important part of Marconi’s successful system of wireless telegraphy. In fact the coherer first made wireless telegraphy possible. It serves as receiver being placed in series with a relay actuating a Morse sounder.
When electrical waves, sent out at a distant station according to an established code, impinge upon it, its resistence diminishes sufficiently to enable the relay to act and this in turn reproduces the signals in the sounder. A tapper automatically restores the resistance of the filings. Dr. Branly has given the name of radio-conductors to bodies which, like filings, can be made conductors or non-conductors at will.
A number of other forms have since been devised, and he himself has found that the tripod coherer, composed of a metal disk making contact with a polished steel plate by means of three steel legs, is more sensitive and uniform in its action than the tube coherer. He has also applied his radio-conductors to “telemechanics without wires”, i. e. to the production of divers mechanical effects at a distance by means of electrical waves.
Eugene Edouard DEsirE Branly has been the very first man in the world able to perform a remote actuation on a mechanism, through the walls, without any hardware link.
As seen in the figure (left) the device, later dubbed the “coherer” by Sir Oliver Lodge, consisted of a glass enclosure filled with a loosely packed, perhaps slightly oxidized metallic powder, whose resistance turned out to have interesting hysteretic behavior. Now, it must be emphasized that the detailed principles that underlay the operation of coherers have never been satisfactorily elucidated. Nevertheless, we can certainly describe its behavior, even if we don’t fully understand all the details of how it worked.
A coherer’s resistance generally had a large value (say, megohms) in its quiescent state, and then dropped orders of magnitude (to kilohms or less) after an electromagnetic wave impinged on it. This large resistance change was usually used to trigger a solenoid to produce an audible click, as well as to ink a paper tape for a permanent record of the received signal.
To prepare the coherer for the next electromagnetic pulse, it had to be shaken or whacked to restore the “incoherent” high resistance state. Figure (left) shows how a coherer was actually used in a receiver. As can be seen, the coherer activated a relay (for audible clicks) or paper tape inker (for a permanent record) when a received signal triggered the transition to a low resistance state. It is evident that the coherer was basically a digital device, and therefore unsuitable for uses other than radiotelegraphy.
The picture shows the first “receiver” made by Branly himself. The coherer is on the left of the picture. It is serial connected with a battery and a galvanometer. After reseting, the indicator has a vertical position. Before an electromagnetic perturbation, the needle deviates to the left or to the right. After a mechanical shock on the coherer, the galvanometer returns to zero.
Among Dr. Branly’s other researches have been those relating to the effect of ultra violet light upon positively and negatively charged bodies (1890-93), electrical radio-conductivity of gases (1894), etc. It may be noted germ of the “antennae”, employed particularly in long distance telegraphy, may be found in his papers published in 1891.
Dr. Branly became Commander of the Order of St. Gregory the Great in 1899 and was nominated Chevalier of the Legion of Honour in 1900 for “having discovered the principle of wireless telegraphy.” He received the grand prix at the Paris Exposition, 1900, for his radio-conductors, and the prix Osiris, in 1903, from the Syndicate of the Press.
He was also made a titular member of the Pontifical Academy dei Nuovi Lincei. Besides his papers published chiefly in the “Comptes Rendus”, Dr. Branly is the author of a “Cours ElEmentaire de physique” (5th ed., 1905); and “Traite ElEmentaire de physique” (3d ed., 1906). Dr. Branly was three times nominated for a Nobel prize, but he never received it.
Late photos of Eugene Edouard DEsirE Branly
Edouard Branly died on March 24, 1940, his state funeral were celebrated in the presence of the President of the Republic Albert Lebrun.
Branly’s grave in Le Pere Lachaise cemetery, Paris, France
A stele of Edouard Branly in Auderville memorizing his wireless telegraph experiments performed there in 1902.
Bust of Eugene Edouard DEsirE Branly on promenade du luxembourg a Montmartre.