APPENDIX. 31 



normal. At O b 23i m and 2 h 23 m the vertical force was 36 and 32 divisions smaller than the normal. 

 Difference 0.0011 parts of the force. 



XX. 1844, March 29th. At 16 h 51 m cloudy, aurora visible. The declination magnet is deflected 

 to the east and west several times in succession; between 16 h 20 m and 18 h 20 m about 14 divisions E. ( 

 and 16 divisions E. ; the following greatest west deflection of 61 divisions (27') occurred at 20 h 10 m ; 

 the next east deflection reached a maximum at O h 22 m (30th) of 41 divisions; a maximum west 

 deflection was again reached at l h 14 of 50 divisions (23'). The horizontal force is throughout 

 smaller than the normal value, with differences varying on the average from 50 to 70 divisions. The 

 greatest difference was reached at 20 h 2 m of nearly 100 divisions (0.0036 parts of the force); at 23 k 

 47 m another small value of 90 divisions was observed. The vertical force was disturbed from 21 h 

 23 m to 4 h 23i m (30th). Force less 49 divisions, 55, 44, 73, 49, 52, 55, and 31 divisions. Minimum 

 value 0.0024 parts of the force. 



XXI. 1844, April 17th. At 2 h 20 m , although cloudy, it was very bright at the north; same remark 

 at 22 h 20 m . The declination disturbances extend nearly over the whole day. The deflection was at 

 first west (between O h 20 m and 4 h 20 m ) with a maximum value of 48 divisions (22') at 3 h 10 m ; it then 

 changed to the east, at 6 b 04 m it reached 52 divisions (23') ; up to 20 h 20 m the deflection was slightly 

 to the east. The horizontal force was diminished early in the morning, attaining a first minimum at 

 2 h 40 m of 47 divisions; it increased for a short time, reaching at 4 h 14 m 52 divisions above the normal, 

 the force again decreased and reached at 5 k 47 m the lowest value of 151 divisions (0.0055 parts); it 

 remained below the normal value for several hours. At 19 h 53 m the diminution was 41 divisions. 

 Vertical force disturbed from 3 b to 8 h (+23^ m ), force less 52 divisions, 58, 61, 66, 53, and 35 divisions. 

 Minimum value 0.0022 parts of the force. 



XXII. 1845, January 9th. At 17 k 20 m an aurora visible. The declination magnet is deflected 

 east and west alternately; first maximum east deflection at 16 h 32 m of 20 divisions ; following maxi- 

 mum west at 17 h 02 of 11 divisions; following east deflection about 20 divisions 12 m later; next 

 west deflection at 17 h 22 m 21 divisions; at 19 h 56 m the deflection again east 32 divisions; at 21 h 38 

 it is west 40 divisions (18'), at 22 h 20 m it is east 33 divisions. The horizontal force between 15 k 52 m 

 and midnight is considerably smaller than the normal value, a minimum is reached at 17 k 16 m of 155 

 divisions (0.0056 parts of the force). The disturbances ceased between 2 k and 3 k on the morning of 

 the 10th. The vertical force was disturbed at 17 h , 20, 22, and 23 k ( + 23^), force greater 44 divisions, 

 31, 35, and 33 divisions. Average increase 0.0012 parts of the force. 



From the preceding detailed account of the condition of the declination and of the horizontal and 

 vertical components of the magnetic force during auroral displays, we obtain the following general 

 results : Each of the 22 auroras recorded was accompanied by a corresponding disturbance of the 

 earth's magnetism, at least in one of the three elements; in one case the declination alone was 

 affected, in another case only the horizontal force, and in a third only the vertical force. The latter 

 force was less subject to disturbances than the other two elements. 



In the following table, showing the condition of the magnetic components during auroras, the first 

 column contains the number of the aurora, the second the amount of declination deflection, the third 

 its direction or the successive large excursions of the north end eastward or westward, the fourth the 

 amount of the horizontal force disturbance expressed in parts of that force (a minus sign indicates less 

 force than the normal belonging to that time, a plus sign indicates the reverse), the last column con- 

 tains the amount of disturbance in the vertical force expressed in parts of that force ; the signs have 

 the same signification as for the horizontal force. 

 5 



