134 NORTHERN XIGHTS. [LeSSOn XXIV. 



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in hot countries, and to produce Aurora Boreales 

 alone in cold countries. 



This theory, though plausible, is not, however, 

 entirely free from objections. Mr John Dalton, 

 whose name I mentioned in the Seventeenth 

 Lesson, has advanced a new theory of the Aurora 

 Borealis, in which he has endeavoured to shew, 

 that the luminous beams of this phenomenon are 

 cylindrical, and parallel to each other at least 

 over a moderate extent of country, that these 

 cylindrical beams are all magnetic, and parallel to 

 the dipping-needle at ihe places over which they 

 appear, that the distance of these beams from 

 the earth is nearly equal to their len<nh, that the 

 rainbow-like arches are about i50 English miles 

 above ihe earth's surface, and that the Aurora 

 Borealis is a magnetic phenomenon whose beams 

 are governed by the earth's magnetism. 



LESSON 



