INSTRUCTIONS FOR OBSERVATIONS 



AURORA.* 



GENERAL REMARKS. 



Though the aurora borealis has received attention during a 

 considerable portion of the last two centuries, definite informa- 

 tion is still wanting on several points which may serve as the 

 basis of a sound induction as to its cause. These relate par- 

 ticularly to the actual frequency of the appearance of the 

 meteor; its comparative frequency in the different months of the 

 year and different hours of the day; the connection of the ap- 

 pearance of the meteor with other atmospherical phenomena; 

 the elevation and extent of visibility of the arch; and whether 

 the same or different phases are presented to individuals at 

 different stations at the same moment of time ; finally, the pre- 

 cise influence of the arches, streams, &c., on the magnetic con 

 dition of the earth ; and whether any unusual electrical effects 

 can be observed during the appearance of the meteor. 



Auroral phenomena may be divided into the following classes : — 



1. A faint light in the north, without definite form or bound- 

 ary. 



2. A diffused light, defined by an arch below. 



3. Floating patches of luminous haze — sometimes striated. 



4. One or more arches, resembling the rainbow, of uniform 

 white color, retaining the same apparent position for a consider- 

 able time, and varying in luminosity. 



* These instructions are principally adopted from those used in the 

 Observatory at Toronto, Canada. 



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