On a disturbance of the earth's magnetism : in connexion with the appearance of an aurora borealis, as observed at Albany, April 19, 1831 / by Joseph Henry.
- Joseph Henry
- Date:
- [1832?]
Licence: Public Domain Mark
Credit: On a disturbance of the earth's magnetism : in connexion with the appearance of an aurora borealis, as observed at Albany, April 19, 1831 / by Joseph Henry. Source: Wellcome Collection.
Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)
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![[Extract from the Report of the Regents of the University of the State of New-York, to the Legislature, 1832.] ON A DISTURBANCE OF THE EARTH'S MAGNETISM, IN CONNEXION WITH TOE APPEARANCE OF AN AURORA KOREA LIS, / , AS OBSERVED AT ALBANY, AfBIL 19, 1831. 4 By JOSEPH HENRY, Of the Albany Academy. [Communicated to the Albany Institute, January 26, 1S32.] That the aurora has some connexion with the magnetism of the earth, was asserted as early as the middle of the last century ; and since that time, many observations have been recorded, tending to confirm this position. I, It has been observed, that when the aurora appears near the northern horizon in the form of an arch, the middle of this is not in the direction of the true north, but in that of the magnetic needle at the place of observation; and that when the arch rises towards the zenith, it constantly crosses the heavens at right angles, not to the true, but to the magnetic meri- dian. This fact is most obvious where the variation of the needle is great. 2. When the beams of the aurora shoot up so as to pass the zenith, which is sometimes the case, the point of their conver- gence is in the direction of the prolongation of the dipping needle at the place of observation. 3. It has also been observed, that during the appearance of an active and brilliant aurora, the magnetic needle often becomes restless, varies sometimes several degrees, and does not resume its former position until after several hours. From the above facts, it has been generally inferred that the aurora is in some way connected with the magnetism of the earth; and that the simultaneous appearance of the meteor, and the dis- turbance of the needle, are either related as cause and effect, or as the common result of some more general and unknown cause. 1](https://iiif.wellcomecollection.org/image/b21128121_0003.jp2/full/800%2C/0/default.jpg)
