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Abstract

Shortly after Gauss's absolute method for measuring magnetic fields was invented (1832), and the bifilar device for observations of the geomagnetic field was constructed and put into operation in Göttingen (1837), geomagnetic observations also started at the Prague Clementinum observatory (1839). The beginnings of the observations at Clementinum were tightly connected with Karl Kreil, who become familiar with this new field of science at the Milan observatory. In Prague, he organized regular geomagnetic observations that even went on after his moving to Vienna (1851) to establish the Central Institute for Meteorology and Geomagnetism. The regular measurements in Prague persisted until 1917. The results were printed in yearbooks Magnetische und Meteorologische Beobachtungen zu Prag. The measurements were carried out manually. The declination was observed using the magnetic compass principle, while a bifilar apparatus was used to measure the horizontal intensity. Data from the period 1839-1871 were published in the divisions of the scale of the instrument. These data we analysed, transformed to physical units and made available to the users. In addition to regular daily observations, two categories of data with a higher cadence were provided in the first decade: (1) magnetic storms and (2) joint measurements organized in the frame of Göttingen Magnetic Union. In addition to the observatory practice at Clementinum, in the period 1843-1845, Kreil also carried out a magnetic survey in Bohemia, the first survey of this sort in the Central Europe. In the following years he continued the survey in other parts of the Austrian Empire.