Observations qf the Aurm-a Borealis. 4!65 



occur in the intervals, will be able to state every morning 

 whether aurora has been seen at all during the night, and if 

 not, whether the state of the sky was favourable or otherwise 

 to observation. Private observers should make a regular 

 practice of looking for auroras, every clear evening, from dusk 

 to as late an hour as may be convenient, recording the result 

 whether there has been an aurora or not, together with the 

 times of observation. The notes may be short, but they 

 should be clear and precise. Wet or cloudy evenings should 

 be noted. 



Auroral phaenomena may be divided into the following 

 classes : — 



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

 boundary. 



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



3. Arches resembling the rainbow in size and form, but of 

 a uniform white colour, sometimes retaining their apparent 

 position for a considerable time without change. 



4. "A dark segment under the arch;" if any star can be 

 distinguished within this space, the circumstance should be 

 particularly noted. 



5. " Floating patches of luminous haze or cloud." 



6. Beams, rays, streamers, transverse and serpentine bands, 

 sometimes tinged with colour, and undergoing more or less 

 rapid changes. It may be necessary to define the last two 

 expressions. Transverse bands are frequently nothing more 

 than arches which have advanced nearly to the zenith, or 

 perhaps have passed it, and retain their I'egularity of form, 

 although now projected nearly as straight lines. Serpentine 

 bands rather resemble curtains of light, and undergo in their 

 outline changes like those of the folds of a curtain. They 

 are usually the most brilliant part of a display. ^^j ",„^^.-„ 



7. " Auroral corona, or a union of beams a few degrees to 

 the south of the zenith." 



8. " A sudden appearance of dark clouds" in the region 

 recently occupied by the aurora. 



9. " Sudden appearance of haze over the whole face of the 

 sky." 



10. Lastly, a disposition in light clouds at a great elevation 

 to arrange themselves during daylight in parallel lines, cross- 

 ing the meridian at right angles, has been frequently suspected 

 to be connected with the aurora, or with a common source. 



The observer should state in plain and definite language 

 the general character of the aurora, with reference more par- 

 ticularly to the foregoing characteristics. At Canadian sta- 

 tions every observation of the azimuths of the extremites of 



