POLAT? LIGHT. . 



they are not rather, as has been conjectured by Franklin, 

 Richardson, and myself, the effect of a meteorological process 

 generated by and accompanying the magnetic storm. The 

 regular coincidence in respect to direction between the very 

 fine cirrous clouds (polar bands) and the magnetic declination, 

 together with the turning of the points of convergence, were 

 made the subjects of my most careful observation on the 

 Mexican plateau in 1803, and in Northern Asia in 1829. 

 When the last named phenomenon is complete, the two ap- 

 parent points of convergence do not remain stationary, the 

 one in the north-east and the other in the south-west (in 

 the direction of the line which connects together the highest 

 points of the arch of the polar light which is luminous at 

 night), but move by degrees towards the east and west. 12 

 A precisely similar turning, or translation of the line, which 

 in the true Aurora connects the highest points of the lumi- 

 nous arch, whilst its bases (the points of support by which it 

 rests on the horizon) change in the azimuth and move from 

 east-west towards north-south, has been several times ob- 

 served with much accuracy in Finmark. 13 These clouds ar- 



12 I will give a single example from my M.S. journal of my Siberian 

 journey: "I spent the whole of the night of the 5 6th of August 

 (1829), separated from my travelling companions, in the open air, at 

 the Cossack outpost of Krasnajazarki, the most eastern station on the 

 Irtisch, on the boundary of the Chinese Dzungarei, and hence a place 

 whose astronomical determination was of considerable importance. 

 The night was extremely clear. In the eastern sky polar bands of 

 cirrous clouds were suddenly formed before midnight (which I have re- 

 corded as ' de petits moutons eyalement espaces, distribute en bandes 

 parall&les et polaires)' . Greatest altitude 35. The northern point of con- 

 vergence is moving slowly toward the east. They disappear without reach- 

 ing the zenith ; and a few minutes afterwards, precisely similar cirrous 

 bands are formed in the north-east ; which move during a part of the 

 night, and almost till sunrise, regularly northward 70 E. An unusually 

 large number of falling stars and coloured rings round the moon 

 throughout the night. No trace of a true Aurora. Some rain falling 

 from speckled feathery masses of clouds. At noon on the 6th of 

 August the sky was clear, polar bands were again formed, passing from 

 N.N.E. to S.S.W., where they remained immoveabie, without altering 

 the azimuth, as I had so often seen in Quito and Mexico." (The mag- 

 netic variation in the Altai is easterly.) 



13 Bravais, who, contrary to my own experience, almost invariably 

 observed that the masses of cirroup clouds at Bossekop were directed, 

 like the Aurora borealis, at right angles to the magnetic meridian 

 (Voyage* en Scandinavie, Phenomene de translation dans les pied* de 



