550 



APPENDIX. 



[No. III. 



ment. It was twice accidently shaken, but re-adjusted each time, without 

 being moved out of its place : these circumstances are noted in the table, and 

 asterisks are placed against observations that were made when the bubble 

 shewed a slight deviation from the horizontal position, the adjustment, then 

 required, was made after the observation had been read off. 



For the convenience of reading off, the compas s was placed on the stand 

 with the north end of the needle, pointing to 348° 30' at three p. m. ; and the 

 observations, made with the graduated circle in this position, are given in the 

 following tables, together with the temperatures, and some brief notices of the 

 weather. It must be recollected that this point of 348° 30', is preserved merely 

 for the sake of referring to the original observations, and that it has no con- 

 nexion whatever with the degrees indicating the bearings which will be here- 

 after given of the Aurora. 



Before adverting to the effect of the Aurora on the needle, I must premise, that 

 the arch-like appearance of the Aurora, noted in the daily remarks, did not 

 always resemble a portion of a great circle ; but, on the contrary, frequently 

 crossed the zenith, without originating and terminating in opposite points of 

 the horizon ; and although the general arrangement of the parts gave the idea 

 of an arch, yet this arch was frequently broken, and its portions disconnected. 



The colour of these arches varied from grey to a lively yellow, and in clear 

 weather, the light emitted was generally observed to be more brilliant and 

 dense than when an opposite state of the atmosphere existed. 



The horizontal bands or masses of light, mentioned in the notes, appeared 

 indiscriminately in every quarter of the sky, and at different elevations ; they 

 more frequently originated or terminated in the magnetic east or west, but not 

 invariably so, and we have seen them on more than one occasion begin and end 

 in the magnetic meridian. Their light varied much in density, and was gene- 

 rally of a yellowish hue. 



The arches and horizontal bands of Aurora occasionally separated into parts 

 or beams, which had a quick lateral motion. At such times, the colours were 

 generally most vivid, and now and then prismatic. The extremities of these 

 beams did not appear to point uniformly to any particular part of the sky, but 

 to depend entirely upon the direction of the arch which they composed. 



The term " beam," used in the notes, does not always allude to the appear- 

 ances just mentioned, but is also applied to the commencement of an arch 



