71 



3. This centre of converging rays was easily seen to be about 

 20'> South of the zenith of York : it was also considerably to 

 the East of the meridian, and remained apparently constant for 

 an hour and a half. At 10 hours p. m. it was near the star 

 Mirach ; at 10-20 appeared pretty exactly to coincide with it ; 

 at 11 it was certainly on the East of it. Hence it may be com- 

 puted that the pole of the auroral beams was in a great circle 

 crossing the meridian of York, from about 27° 30' West of North, 

 to about 27° 30' East of South, and distant from the zenith 22° 

 S. S. E. nearly. Now this point differs from that to which the 

 South pole of the Dipping Needle points at York, only about 

 2| degrees in altitude and ^\ degrees in Azimuth. There can 

 be no doubt then that this, like other carefully measured au- 

 roral exhibitions, was arranged in magnetic lines." 



The Author then compared with these results various 

 other notices of the phenomenon, at Durham (by Professor 

 Chevallier), at Nottingham (by Mr. Lowe), at Cambridge (by 

 Professor Challis), at Bath, Brighton &c., and showed the bear- 

 ing of the whole on the well known Daltonian theory of the 

 Aurora, (1796), which, in its leading points, was found to be 

 strongly supported by them. As a basis for a comprehensive 

 view of the whole subject, the Author submitted the following 

 propositions. 



1. "That by reason of the unequal and systematically vari- 

 able distribution of heat and moisture over the land and sea, 

 and through the atmosphere, electric tensions and polarities 

 arise, which occasion instantaneous sparks (hghtning) in those 

 (lower) parts of the atmosphere which resist heat, and silent 

 currents (auroral beams) in the regions above the clouds. 



2. That these currents may be regarded as of indeterminate 

 direction towards the upper or most attenuated regions in which 

 no attracting objects exist, and in consequence, assume positions 

 which depend only on the earth's magnetism; each beam 

 representing an electrical magnet and having its axis parallel 

 to the Dipping Needle. Hence thousands of such beams, a 

 thousand miles apart, may exhibit many local coronse, such as 

 were noticed in October, each symmetrical to the magnetic axis 

 of the place of observation." 



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