Page:Polar Exploration - Bruce - 1911.djvu/226

222 the magnetic work, found that the declination of the magnetic needle was disturbed by the presence of the aurora.

This interesting observation was by no means a new one, for in 1741 Celsius and Hiorter noted for the first time the simultaneity of the Aurora Borealis and the disturbances in magnetic declination. From 1741 to 1747 Hiorter recorded forty-six examples of this coincidence. At the suggestion of Celsius, Graham made corresponding observations in Britain, and it was found that the magnetic disturbances were synchronous on the same days in Sweden and Britain. These observations were followed up by Wargentin, Canton and Wilcke. Wilcke found that every time, or almost every time, there was a magnetic disturbance, that disturbance was accompanied by a display of Aurora Borealis; but the inverse was not found to be the case, that is to say, the Aurora Borealis might be observed without any disturbance of magnetic declination accompanying it. Between 1771 and 1774 Wilcke proved that the inclination of the needle was also affected and that the centre of the corona corresponded with the magnetic zenith.

Humboldt, in 1806, discovered that there was a relationship between the magnetic force and the Aurora Borealis. In 1834 the Magnetic Association founded by Gauss and Weber,