HAJÓS

HUNGARY (see also List of Individuals)

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14.5.1853 Mágócs/H - 8.2.1927 Budapest/H

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After graduation in 1876 from the Pest University of Technology, Sámuel Hajós started his practical activities with geodetical survey works in the capital Budapest. He joined the State Services in 1880. From 1886, Hajós worked in the Department of Hydrography, as one of its founders and later as its head. His results became internationally known in terms of tool development, mainly to determine water velocity and discharge of rivers. His principal work is the book Hydrometry published in 1906.

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Hajós was an expert in river gaging, which from the 1880s developed particularly in the Danube River scheme as a part of hydrometry. The telemetric gauge was first presented at the Hungarian National Exposition in 1885 and then praised for its advantages for continuous and accurate water stage registration. This device recorded the actual stage of Danube River on a receiver located in the great exhibition hall. The long contact required for the gauge to work was assured by a clockwork and a pneumatic device similar to that applied for automated door-locks. In 1896 Hajós presented during the Millennium Exhibition the electric gauge: A thin wire was laid on a pulley rotated by a float. A metal hand of an accurate clock moved in front of the pulley and by touching the metal plate an electric circuit was closed. At the receiving station a horizontal drum made an arm plot a dot on the paper strip in all the instances when the circuit was closed. On the paper drum the dots line up in accordance with the variation of the stage, at intervals of about an hour. The stage registration could be subject to temporal variation by changing the contact between the clock hand and the metal plate. Hajós also added to the definition of the stage-discharge curve by novel designs of current meters. The rating equations were experimentally determined until 1894 in a closed reach of the Tisza River. From then a calibration station was set up at the Millér Canal; it was 150 m long and 1.20 m wide and allowed accurate propeller rating.

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_{Anonymous (1967). S. Hajós. Magyar életrajzi lexikon 1: 660. Akadémiai Kiadó: Budapest. P}

_{Hajós, S. (1893). Actual situation of water velocity measurement. Vizrajzi Evkönyv 8: 67-85 (in Hungarian).}

_{Hajós, S. (1898). Jaugeages en Hongrie. Annales des Ponts et Chaussées 68(3): 307-329. Hajós, S. (1901). On the rating of current meters. A Magyar Mérnök és Epítész Egylef Közlönye 35(7): 381-395 (in Hungarian).}

_{Hajós, S. (1902). On the rating of current meters. Vízrajzi Évkönyv 11: 17-32 (in Hungarian). Stelczer, K. (1986). 100 years hydrological service in Hungary. VITUKI: Budapest.}