Technikatörténeti szemle 16. (1986-87)

TANULMÁNYOK - ifj. Bartha lajos: A mágneses deklináció korai adatai a Kárpát-medencében

A szerző e helyen köszöni meg a szóbeli információkat és adatszolgáltatásokat Dr. Barta György akadémikusnak, Dr. Willem Hackmannak (Museum of the History of Sciences, Oxford), Hans-G. Körber úrnak (Berlin), Prof. Dr. Miecislaw Markowskinak (krakkói Egyetem) és Ph.D. Anita McConnelnek (Science Museum, London). Külön köszönet illeti Fleck Alajost, a PGTV ny. tud. főmunkatársát, aki — mint sok más tanulmányomat is — ezt a munkát is hasznosan segítette tanácsaival, gondolataival. LAJOS BARTHA: EARLY DATA ON MAGNETIC VARIATION IN THE CARPATHIAN BASIN It is now undoubted, that the deviation of the magnetic needle from the N

—S direction — the magnetic declination or variation — was first observed by sundial makers. Georg Peuerbach and his student, Johannes Regiomontanus designed several instruments with combass both in the University of Vienna and in Buda. Hans Dorn (b. cca. 1425, d. 1509) — another student of Regiomontanus and Peuerbach — attached compasses to his instruments made between 1451 and 1500 variation direction and angle by an engraved line. At present, seven instruments are known wich were made by Hans Dorn in Buda, between 1476 and 1490. The mean value of the variation for the 15 years, reffering to 1484 is +12°. (The positive sign aindicates eastern declination.) On the suncompass made in Nagyszeben (Herrmannstadt in german, today: Sibiu, Romania) by Michael Wolf and Martinus Fenich in 1576, a variation of D = —18,5° (western) can be read. The first written datum on magnetic variation in the Carpathian basin appears on the view of Eperjes (today: Presov, Czechoslovakia) from around 1660. The engraving was made as a cover page for J. Bayer's 'Ostium vel Atrium Naturae', 1662. It was Israel Hibner (b. Sneeberg, Saxonia, 1619, d. Nagyszeben, 1668) who prepared the engraving showing the view of Eperjes and determined the magnetic variation with a value: —30,5°. Luigi Ferdinando Marsigli (Bologna, b. 1658, d. 1730) a humanist cholar, military engineer carried out observations of geomagnetism in Hungary in 1696 first of all. The measurements of Marsigli in Hungary on seven points resulted in values between —9°15' (for Titel) and 10° (for Baja and Szeged). The significance of Marsigli's measurements is also underlined by the appearance of the data on Edmond Halley's second isogonic map published in 1702. Samuel Mikoviny (Pozsony, b. 1700, d. 1750) Hungarian engineer and cartographer measured the variation in Pozsony, with a value of —12°30' (W deviation), in the year 1728. István Tőke (b. ?, d, 1768), teacher of the Kalvinist college in Nagyenyed (Transylvania; today: Aiud, Romania) determined magnetic variation around 1735. He observed a deviation around —10°. The town plans view surveyed by Austrian Emperial military engineers are almost contemporaneous the magnetic measurement in Nagyenyed. Variation is shown an the wind-roses of map sheets of Brassó (Cronstadt, today: Bragov, Romania) with a deviation: —9,1°; Medgyes (Mediasch today: Media?) —12,1° and —10° for Segesvár (Schassenburg, today: Sighisoara). The chart of secular change gives unambigous evidence to the old observation that date of extreme variation value shifts from east to west in time. In Central an Eastern Europe the angle of E-variation first decreased repidly from 1450, variation was 0° around 1530—1550. During the late 16. c. the rate of change was reduced and between 1660 and 1720 its trend turned to the opposite with slow rate. From 1720 the value of W-variation grew again rapidly and reached its maximum of —16,3° W-deviation in Buda in 1790.