reader, partly by putting in stop marks, partly by explaining vocabulary in our comments. Sometimes extra words have been put into our translations in [brackets]. In the same vein, all quotations from printed texts in languages other than English have been translated. The original Latin, German, Swedish, Norwegian, or Danish wordings are found in the publications referred to. The spelling of names of places has in many cases changed considerably since the 18thcentury, and for minor places the spelling also was somewhat haphazard. We have therefore used the modern versions even in quotes. Figure 3 Title page of Hell’s “astronomical notebook”, the manuscript referred to as MS Hell c in this report.
14 The magnetic observations in Vardø Hell measured the declination of the magnetic needle, i.e. the angle between the needle and geographic north. Traditionally this angle is denoted “west” when the needle is pointing west of north and “east” when it is on the other side. At Hell’s time the declination in northern Norway was westerly everywhere, and Hell in his manuscript usually skips the “west” designation. In modern geomagnetic terminology declination is reckoned positive towards east and negative towards west. In our tables and figures of Hell’s numbers this modern convention is used. His numbers therefore appear as negative. Today the declination in this region is positive (east). Hell’s instrument for observing the declination is in principle a compass: a magnetic needle allowed to move freely on a vertical axis. However, the task of measuring declination is quite different from that of setting the course of a ship: Whereas the mariner’s compass tells the direction in a straightforward manner, measuring declination implies the double task of first finding north by astronomical methods, and then observing the deviation of the magnetic needle. The design of the instrument is therefore noticeably different from that of an ordinary compass, and the designation declinometer is used instead. This term was used also in the 18thcentury. Observations of magnetic inclination probably was also on Hell’s scientific programme. His outline of the planned Expeditio litteraria ad Polum Arcticum has no reference to magnetic inclinations, but in a letter to Horrebow of 12thNovember 1768 (Pinzger 1927, p. 31) and in another to Schøller39of 1stJanuary 1769 (ibid, p. 42), he expresses intention to measure inclination as well as declination. Finally, in a letter of 30thApril 1769 to Count Thott40(ibid, p. 96) he explicitly states that such recordings were done routinely. An entry in the diary of Sajnovics seems to corroborate that they at least tried to observe inclination (MS Sajnovics 18thMay 1769): A tent was put up, and on a table inside the meridian line was drawn for the exploration of the magnet’s inclination. However, shortly afterwards it was overturned by a pig.
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- Fall '19
- Magnetic Field, Earth's magnetic field, Magnet, Compass, Transit of Venus, Father Maximilian Hell