47° 



POPULAR SCIENCE MONTHLY. 



slow-moving forms are white, lined with yellow, milky and difficult 

 to define. Rose carmine is the next most noticeable color. In the 

 rapid-moving arcs, crowns, wreaths and draperies, the center is 

 usually yellowish, one extremity red, the other green. The red is 

 almost always toward the lower part and also in the direction to 

 which the ray moves, while the green is above and behind. For 

 instance, if a ray darts down from a crown, the lower end will be red, 

 the upper green. These colors will be very brilliant; when the red 

 is very brilliant, the green is as intense. The red remains longest 

 and fades last, when fog obliterates the aurora finally. 



Our author, it will be seen, is a close observer, and furnishes 

 reasons for all his deductions. He has discovered that the brilliance 



Fig. 2. — Wintering of the '' Vega." Multiple Arcs with Different Centers. 



of the colors bears a definite relation to the state of the atmosphere. 

 In high latitudes. Sir John Franklin, McClintock, Weyprecht, and 

 others aver that the coloring of the aurora was less strong when the 

 air was very pure, and increased when it became foggy. The fine 

 drapery forms are generally seen where seas are open in winter, free 

 from ice, hence subject to fogs, as in Norway, Spitzbergen, and 

 ^Newfoundland. 



The light from auroras is very feeble; only a few lines of print 

 can be read; while by the light of the full moon this is easy. The 

 intensity of the aurora rarely exceeds the light of the moon in her 

 first quarter, even in the arctic regions ; this is corroborated by Parry, 

 Kane, Hayes, Nordenskiold, and others. Auroras are less frequent 

 in the full of the moon, paling in her effulgence, which drowns the 



