150 COSMOS. 



logical process generated by and accompanying the magnetic 

 storm. The regular coincidence in respect to direction be- 

 tween the very fine cirrous clouds (polar bands) and the mag- 

 netic declination, together with the turning of the points of 

 convergence, were made the subjects of my most careful ob- 

 servation on the Mexican plateau in 1803, and in Northern 

 Asia in 1829. When the last-named phenomenon is com- 

 plete, the two apparent points of convergence do not remain 

 stationary, the one in the northeast 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 lumin- 

 ous at night), but move by degrees toward the east and west.* 

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

 in the true aurora connects the highest points of the lumin- 

 ous arch, while its bases (the points of support by which it 

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

 east-west toward north-south, has been several times observed 

 with much accuracy in Finmark.* These clouds, arranged 



* I will give a single example from my ISIS, journal of my Siberian 

 journey: "I spent the whole of the night of the 5-Gth of August 

 (1829), separated from my traveling 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 

 recorded as * de petits moutons egalement espaces, distribues en bandes 

 par alleles et polaires).' Greatest altitude 35°. The northern point of 

 convergence is moving slowly toward the east. They disappear with- 

 out reaching the zenith ; and a few minutes afterward precisely simi- 

 lar cirrous bands are formed in the northeast, which move during a 

 part of the night, and almost till sunrise, regularly northward 70° E. 

 An unusually large number of falling stars and colored 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, pass- 

 ing; from N.N.E. to S.S.W., where thev remained immovable, without 

 altering the azimuth, as I had so often seen in Quito and Mexico." 

 (The magnetic variation in the Altai is easterly.) 



f Bravais, who, contraiy to my own experience, almost invariably 

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

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

 ( Voyages en Scandinavie, Phenomene de translation dans les ]>ieds de Tare 

 des Aurores Boreales, p. 534-537), describes with his accustomed ex- 

 actitude the turnings or rotations of the true arch of the Aurora Borea- 

 lis, p. 27, 92, 122, 487. Sir James Ross has likewise observed in the 

 southern hemisphere similar progressive alterations of the arch of the 

 aurora (a progression in the southern lights from W.N. W. — E.S.E. to 

 N.N.E. — S.S.W.), Voyage in the Southern and Antartic Regions, vol. i., 



