248 TENTH ANNUAL REPORT OF 



2. Note the time of observation, and compare the watch used with 

 a good clock, as soon after as is convenient. 



3. Make a return of the latitude and longitude of the station. 



4. Note the class to which the auroral phenomenon belongs. 



5. If it be an arch, note the time when the convex side reaches any 

 remarkable stars, when it passes the zenith, disappears, &c. 



6. If the arch be stationary for a time, mark its position among the 

 stars on the accompanying map, so that its altitude may be determined. 



7. If it be a streamer or beam, mark its position on the map, and 

 the time of its beginning and ending. 



8. If motion be observed in the beams, note the direction, whether 

 vertically or horizontally, to the east or west. 



9. Note the time of the formation of a corona, and its position 

 among the stars. 



10. Note the time of the appearance of any black clouds in the 

 north near the aurora ; also, if the sky be suddenly overcast with a 

 mist at any time during the auroral display. 



11. Give the direction and force of the wind at the time. 



12. Note if any electrical effects are observed. 



13. Note the effect upon a delicately suspended magnetic needle. 



USE OF THE MAP.* 



1. To define the place and the extent of the aurora, the observer 

 should familiarize himself with the relative position of the stars in the 

 northern sky, by frequent inspection of the accompanying map, or a 

 celestial globe. 



2. Let the observer place the map before him, with the constella- 

 tions in the j)ositions in which they actually appear at the time of the 

 observation. This may be done by holding up a plumb-line between 

 the eye and the pole star, noticing the stars which it cuts; then a 

 light pencil drawn through these stars and the pole on the map will 

 be the centre of the heavens,, or place of the meridian at the moment. 



3. Mark carefully the place among the stars of the arch of the au- 

 rora, and show its v/idth by jiarallel curved lines. Make a note of 

 the time. 



4. Draw a light curved line, following, as nearly as can be judged, 

 the outline of the arch down to the horizon, on each side. 



5. If the arch changes its position, mark its new places at intervals, 

 noting the time of each observation. 



G. Letter each position A, B^ C, &c., and note the time and other 

 particulars on the back or margin of the map, or in the register. 



7. Beams or corruscations, or streamers of white or colored light, 

 may be marked by lines at right angles to the above, with arrow 

 heads pointing towards the place among the stars to which they tend, 

 or where they would meet, if prolonged. 



8. To aid in the estimation of angular distances the spaces between 

 certain conspicuous stars have been marked on the map, which will 

 furnish a scale to assist the eye, when actual measurement may be 

 impracticable. 



9. The course of brilliant meteors, when they fall within the por- 



* Copies of the map will be furnished by the Institution. 



