and Nature of the Cosmic Electric Rays. 57 



of 354 band-forms. The average direction (azimuth) of the 

 three principal band-forms is given in Table VJI. 



Table VII. 



.Form. a. a m . 



Diffuse Arcs and Split Bands 72°49' 101°'3 



Drapery-shaped Arcs 72° 29' 100°-9 



Draperies 103° 24' 13l°-9 



Mean of all except draperies 72° 40' 101°"1 



a is the astronomic azimuth, 

 a m is the magnetic azimuth, and 



d/n — — a Am , 



where A m is the azimuth of the magnetic meridian which 

 is referred to the axis-point. For Haldde we find for the 

 year 1914 



We see that the average magnetic azimuth of the band- 

 forms comes out greater than 90°, or the auroral bands are 

 not directed along the magnetic parallels (referred to the 

 axis-point), but their westward directed ends point about 11° 

 to the north of this direction. If this deviation from the mag- 

 netic parallel was due to the " Spiral form," it would mean 

 that the cosmic rays had a negative charge. 



On account of the interest attached to the question re- 

 garding the direction of the band-forms, we have tried to 

 find the direction from the material collected by previous 

 arctic expeditions, 



Very careful measurements were undertaken by the 

 French commission at Bossekop (near Haldde) in 1838-40. 

 They observed the highest point of the arc, and we may 

 assume the arc on an average to be perpendicular to this 

 direction. This fairly accurate method was later adopted 

 by Oarllieim-Gyllnesldold at Cap Thordsen (Spitsbergen) 

 1882-83, by von Bobrik at Jan Mayen 1882-83, by Westman 

 at Bay Treurenberg 1899-1900, and at the German station 

 Nain 1882-83. Adam Poulson at Godthaab found the 

 direction from drawings of the arcs made on a celestial 

 chart. For a number of other arctic stations of the polar 

 year the directions were merely given in the descriptions 

 and expressed in terms of the directions on the compass card. 



