Aurora Borealis mi the Magnetic Needle. 198 



observations began in March 181B, and were, with the exception 

 of J 81 6, continued till 1821, and the numerous agitations of the 

 magnetic needle which he observed, were diligently compared 

 with the state of the weather. All these observations have been 

 given to the world, and by their means it is in the power of any 

 philosopher to study the relation between the irregularities of 

 the needle, and the meteorological or electrical phenomena of 

 the atmosphere. He can compare these irregularities with the 

 Aurorae which took place between Hackney, (near London,) 

 and Thurso in the north of Scotland, a distance of seven de- 

 grees of latitude, in which a much greater number of Aurorae 

 must have been observed than in the same distance of seven 

 degrees which intervenes between Paris and Leith. As 

 Aurorae are almost always recorded in the English and Scotch 

 magazines and newspapers, it would be useful to science if M. 

 Arago would enter upon this examination. If he does so, the 

 general result will be this : He will find a certain number of 

 the agitations of the needle accompanied with Aurorae Boreales: 

 He will find a certain number of Aurorae which were not ac- 

 companied with any irregular indications of the needle ; and 

 he will find a great number of agitations of the needle which 

 were not attended with Aurorae, but which, as Colonel Beau- 

 foy has stated, were accompanied or followed by squalls and 

 gales of wind, principally from the southern quarters of the 

 horizon. 



We come now to M. Arago's own observations. In the 

 Royal Observatory of Paris there is a delicate magnetic needle, 

 the variations of which have, we believe, been carefully ob- 

 served for some years ; but the series of observations which 

 are made with it have never been published ; and though M. 

 Arago is the editor of a monthly journal, and prints regularly 

 all the meteorological observations made in the observatory, 

 yet the Jar more important magnetic observations, upon the 

 authority of which he builds theories and utters prophecies, 

 are withheld from the public eye. At particular times he ob- 

 serves agitations of this needle, and he predicts that an Aurora 

 has happened in the north. At another, time he reads in the 

 EngUsh journals the account of Aurorae, and looking back to 



