194 COSMOS, 



an elevation of 3000 or 4000 feet ; and, in all probability, 

 the northern lights at different times occur at very different 

 elevations.* The most recent observers are disposed to place 

 the phenomenon in the region of clouds, and not on the con- 

 fines of the atmosphere ; and they even believe that the rays 

 of the aurora may be affected by winds and currents of air, if 

 the phenomenon of light, by which alone the existence of an 

 electro -magnetic current is appreciable, be actually connected 

 with material groups of vesicles of vapour in motion, or more 

 correctly speaking, if light penetrate them, passing from one 

 vesicle to another. Franklin saw near Great Bear Lake a 

 beaming northern light, the lower side of which he thought 

 illuminated a stratum of clouds ; whilst, at a distance of only 

 eighteen geographical miles, Kendal, who was on watch 

 throughout the whole night, and never lost sight of the sky, 

 perceived no phenomenon of light. The assertion so fre- 

 quently maintained of late, that the rays of the aurora have 

 been seen to shoot down to the ground between the spectator 

 and some neighbouring hill, is open to the charge of optical 

 delusion, as in the cases of strokes of lightning or of the fall of 

 fire-balls. 



Whether the magnetic storms, whose local character we 

 have illustrated by such remarkable examples, share noise as 

 well as light in common with electric storms, is a ques- 

 tion that has become difficult to answer, since implicit con- 

 fidence is no longer yielded to the relations of Greenland 

 whale-fishers, and Siberian fox-hunters. Northern lights 

 appear to have become less noisy since their occurrences 

 have been more accurately recorded. Parry, Franklin, and 

 Richardson, near the North Pole ; Thieiiemann, in Iceland , 

 Gieseke, in Greenland ; Lottin and Bravais, near the North 

 Cape ; Wrangel and Anfou on the coast of the Polar Sea, 

 have together seen the aurora thousands of times, but never 



* Farquharson in the Edinburgh Philos. Journal, vol. xvi. p. 304; 

 Philos. Transact, for 1829, p. 113 



[The height of the bow of light of the aurora seen at the Cambridge 

 observatory March 19, 1847, was determined by Professors Challis, of 

 Cambridge, and Chevallier. of Durham, to be 177 miles above the sur- 

 face of the earth. See the notice of this meteor in An Account of tht 

 Aurora Boreali* of Oct. 24. 1847, by John H. Morean. Eso.. 1$48.] 

 Tr 



