420 Scientific Intelligence, — Meteorology, 



realis and terrestrial magnetism a general connection, which no 

 one now doubts, than with the view of supplying additional in* 

 formation concerning the intimate nature of the phenomenon^ 

 and the geometric methods by which its absolute height has 

 sometimes been determined. 



These methods, founded upon the combinations of parallaxes, 

 suppose that every where the same arc is seen, by which I mean 

 the same material particles congregated into a radiating condi- 

 tion by unknown causes. This hypothesis, unless I am deceived> 

 when examined with becoming scrupulosity, will be found to 

 be beset with many well-grounded difficulties. 



The magnetic bearing of the aurora horealis arch proves 

 nothing more than that the phenomenon is placed symmetrically 

 in relation to the magnetic axis of the globe. As to the kind 

 of displacement which the centre of the cupola undergoes for 

 every change of the observer's position, it cannot be explained 

 by the play of the parallaxes This displacement is such that 

 an observer who proceeds from Paris towards the north mag- 

 netic pole, sees the centre of the cupola, situated to the south of 

 his zenith, elevate itself more and more above the horizon ; but 

 precisely the contrary would happen if the cupola were a radu 

 ating point, and not a simple effect of perspective. 



So soon as it is established that in the aurora borealis, one of 

 the portions at least is a mere illusion, we do not perceive why 

 we are at once to adopt the notion that the luminous arc of Paris 

 is that which will be perceived at Strasburg, at Munich, Teeri- 

 na, &c. And what an immense step would be made in the the'- 

 ory of these mysterious phenomena if it were established that 

 each observer sees, as it were, his own aurora borealis, as each one 

 perceives his own rainbow ? And what would this be else than 

 freeing our meteorological catalogues of a multitude of the de- 

 terminations of elevation which cannot be considered as having 

 any real foundation, though they have for their authors such 

 men as Mairan, Halleyy Krafft, Cavendish^ and Dalton. 



Before bringing this article to a close, in which the question 

 of the absolute height of the matter in the midst of which the 

 aurora borealis is formed has been introduced, I ought not to 

 omit to state, that on one occasion Captain Parry had the con- 

 viction that he witnessed the luminous jets proceeding from the 



