Blondel, André Eugène

(b. Chaumont, France, 28 August 1893; d. paris, France, 15 November 1938)

physics, engineering.

Blondel came from a family of Burgundian magistrates. His mother died when he was nine, and his education was directed entirely by his father. He completed his secondary studies in Dijon, entered the École poly technique in 1883, and then attended the École des points et Chaussées. Upon graduation in 1888, he chose assignment to the Service Central des Phares et Balises. Blondel received his degree in mathematical sciences in 1885, and in physical sciences in 1889. He worked in Corn’ laboratory at the École polytechnique in 1888–1889, and there acquired the knowledge that gave rise to his subsequent discoveries.

Blondel’ very first projects drew attention to him, and in 1893 he became a professor of electrotechnology at both the École des Mines and the École des pons et Chaussées.

During the last few years of the century, Blondel, who until then had enjoyed excellent health, participated in sports, and traveled extensively, was stricken with paralysis of the legs, probably of psychosomatic origin. His father then settled near him in Paris. Bedridden, Blondel devoted himself wholeheartedly to his research and inspired a group of associates who worked in the research laboratory he had set up in Levallois.

His health improved somewhat around 1919, after the death of his father. His physical activity remained extremely limited, however, for the rest of his life.

Blondel indicated that all his work had been suggested by his research for the Service des Phares and his teaching of electrotechnology. This explains the tremendous variety of subjects he dealt with (more than 250).

His two main contributions are the oscillograph and the system of photometric units of measurement Struck by the outdated units of measurement used in photometry, Blondel specified, in 1894, different units for this branch of optics. He introduced the fundamental concept of luminous flux and defined illumination according to the flux received by the unit surface. He thus established a coherent system of units, using as a basis the Violle candle and the meter. The unit of flux, or lumen, was independent of the unit of length. This system was adopted in 1896 by the International Electrical Congress, meeting in Geneva, and it became the system used by the international Conference on Weights and Measures. It is also included, practically without change in the international system adopted by the eleventh International Conference on Weights and Measures (1960).

Assigned to study the arc lamps used in lighthouses and their feed, he found deficiencies in the prevailing research methods, which did not allow a worker to see instantly the intensity of alternating currents. After a rather unsatisfactory test using a stroboscopic method (1891) he solved the problem by invention of the oscillograph (1893); he perfected two variations, a “soft iron” version and a bifilar one. For forty years these instruments were the most advanced and the most widely used in the study of variable electric phenomena. From the point of view of the moving band, they have been superseded by the cathode-ray tube oscilloscope, but they are no less valuable because of their simplicity and their small bulk.

BIBLIOGRAPHY

Blondel’ oscillograph was patented in April 1897 (no. 266246); the original file is in the Institut National de la propriété Industrielle, Paris. Among his writings is “La détermination de l’intensivé moyenne sphérique des sources de lumière” in L’ éclairage électrique, 2 (1895), 385–391; 3 (1895), 57–62, 406–414, 538–546, 583–586.

Works on Blondel are Louis de Broglie, La vie et l’oeuvre d’ André Blondel (paris, 1944), a lecture given at the annual of the Académie des Sciences, 18 Dec. 1944; Commemoration de la naissance d’ André Blondel, 1863–1938 (paris, 1963), a brochure published for the ceremoney held 15 May 1963 at the Conservatoire National des Arts et Méters. Paris: and Commemoration de l’ oeuvre d’ André Eugène Blondel (Paris 1942), a collection of articles by Louis de Broglie, Camille Guitton, Joseph Bèthenod, Eugène Darmois, Robert Gibrat, and others

Jacques Payen