Aurora Borealis on the Magnetic Needle. 19T' 



philosophers till 1828, when Mr Dal ton kindly relieves him 

 from his dilemma, by sending him an account of an old, a well 

 known, and now forgotten Aurora. 



We now approach the period of sound inquiry, when the 

 magnetic needle and the Aurora Borealis are observed at the 

 same time, and on the same horizon, by men who had no hypo- 

 thesis to support, — who possessed the finest instruments, — who 

 lived among the very beams of the Northern Lights, — and whose 

 attention had been especially directed to the subject now un- 

 der discussion. 



During the different voyages of Captain Parry to the Arc- 

 tic Regions, the phenomena of the Aurora Borealis and of the 

 magnetic needle were carefully observed ; and it is a most 

 singular circumstance, that neither the needle por the electro- 

 meter were in the least degree affected by them, although they 

 were often carefully watched, in order to ascertain this very 

 fact. 



In Captain Parry's third voyage, in 1824-5, a most splendid 

 Aurora was seen, which actually shot its beams between the 

 observer and the land, which was then distant only 3000 

 yards ; — yet did this Aurora exercise no disturbing force on 

 the magnetic needle ! 



" Our variation needles,'" says Captain Parry, " which were 

 extremely light, suspended in the most dehcate manner, and 

 from the weak directive energy, susceptible of being acted up- 

 on by a very slight disturbing force, were never in a single in- 

 stance visibly affected by the Aurorce, which could scarcely fail 

 to have been observed at some time or other, had any such 

 disturbance taken place, the needles being visited every hour 

 for several months, and oftener when any thing occurred to 

 make it desirable.*" 



The observations themselves upon which Captain Parry 

 founds his conclusions are the most numerous, and we hesitate 

 not to say the most correct, that have ever been published. 

 They occupy nearly J^OO pages in the fourth part of the Philo- 

 sophical Transactions for 1 826. Lieutenant Foster has given 

 an abstract of the daily variations of one of the needles for the 

 months of January, February, March, April, and May 1825. 



