INSTRUCTIONS FOR OBSERVATIONS 



OF THE 



AURORA.* 



GENERAL REMARKS. 



THOUGH the anrora 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. 



(48) 



