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At the request of Dr. van Rijckevorsel, I have made in the laboratory of the University of Groningen, during the night between •7-•8 May, observations of the variations of declinations and of the horizontal intensity. The laboratory is quite free from iron, and lies in a garden far from the railway, canals, and frequented streets. In Groningen there are no electric car lines nor electric plants, hence we are undisturbed by stray or "vagabundirende" currents. The variations of declination weredoi:10.1029/te006i003p00128 fatcat:2ued5bg3m5goxpl2jz5zfkulzq