APPENDIX. 29 



disturbances commenced at O h 17^' (loth) and continued to 6 h 17^ m ; force less 68 divisions, 69 

 divisions, 59 divisions, and 38 divisions. Minimum value 111 divisions or 0.0037 parts of the force 

 at 1" 24 m (15th). 



IX. 1842, September 2d. At 2 h 22 m a bright light extending on each side of N. point about 15, 

 and to about 6 above the horizon ; at 2 h 49 m light spreading and becoming more faint ; at 3 h 12 m 

 light faint and gradually subsiding. The declination was very slightly affected, maximum west 

 deflection a,, 3 h 26, 19 divisions (9'). The horizontal force was not disturbed. The vertical force 

 was likewise undisturbed 



X. 1842, November 21st and 22d. A well developed aurora and the best observed of the series. 

 At 22 h 23 m a very luminous arc extending to about 15 above the horizon, and about 90 along it in 

 the north ; 22 h 38 m light slightly increasing; 22 h 53 m a slight decrease of light; 23 h 18 m light alter- 

 nately appearing and disappearing ; 23 h 33 m four streamers of unusual brightness reaching 30 above 

 horizon ; 23 h 36 m light particularly bright in N. W., whence a large streamer of 20 is shooting, also 

 one due north of 15; 23 h 40 m light subsided, no streamers; 23 h 43 m small streamers appearing; 

 23 h 46 ra large streamers attended with great light in N. W. ; 23 h 48 m the arc still remains about 15 

 above hoizon, but has shortened its chord to 30, no streamers ; 23 h 51 m arc scarcely visible ; O h 23 m 

 (22d) two arcs visible ; O h 28 m a large streamer of 20 in length ; O b 36 m considerable light without 

 the arc ; l h 08 m light very faint ; I 1 ' 23 m slight appearances of arc ; l h 33 m faint streamer of 10 ; 

 l h 58 m faint streamer of 20 ; 2 h 48 m a large but faint streamer due N. about 20 in length ; light 

 has nearly disappeared ; 3 h 3 m light scarcely visible ; 3 h 33 no light visible, and readings of instru- 

 ment ordinary. The declination disturbances commenced at 22 h 20 m , and ceased at 10 h 20 m (22d) ; 

 deflections 49 divisions W., 20 divisions W., 25, 20, 8, 25, and 16 divisions E. The maximum W. 

 deflection (22') occurred at the commencement, with the appearance of the luminous arc, the needle 

 remained deflected to the westward until towards the end, when there was a smaller easterly deflection. 

 No special effect of the streamers is noticed. The horizontal force disturbances commenced at 16" 

 22 m , and continued to 2 h 22 m (22d) ; horizontal force less 33 divisions, 68, 82, 183 divisions (0.007 

 parts of the force) ; this diminution was about the time of the appearance of the arc, 125 divisions and 73 

 divisions at the last two regular observing times. The streamers did not appear to have any special 

 effect The horizontal force always remained smaller than the normal value at the respective hours. 

 The vertical component was not affected. 



XI. 1843, May 6th and 7th. At 19" 48 m a bright light ; at 2 h 18 m (7th) light to N. about 23 

 high, but faint. The declination disturbances commenced at 16 h 20 m , and continued to about 3 b (7th). 

 The deflections at the regular hours were 28, 30, 16 divisions E., 15 divisions W. (20 m after midnight), 

 maximum east deflection 18', succeeding maximum west deflection 9', next following maximum east 

 deflection 33', following maximum west deflection 15'. The horizontal force disturbances commenced at 

 the same hour with the declination disturbances, and continued to the end of the series of observations. 

 The change commenced with a violent increase of 113 divisions above the normal value, and increased 

 to 330 divisions (0.012 parts of the force) at 18 h 04 m , corresponding in time to the first maximum east 

 deflection. The force then decreased, reaching 132 divisions below the normal value, and attaining 

 shortly (16 m ) after midnight the extraordinary low value 348 divisions (0.013 parts of the force) ; up 

 to the end of the disturbance the force remained below the standard amount. The vertical force was 

 suddenly disturbed, at 18 h 23 m it was 161 divisions greater than the mean, and at 22 h 23 m bat 41 

 divisions above the normal. Maximum value 164 divisions (equal to 0.0054 parts of the force) 

 at 18" 12 ra . 



XII. 1843, May 8th. At O h an aurora visible to north. The declination was but slightly affected ; 

 at 19 h 32 m there was an easterly deflection of 15 divisions or 7' ; at 20 h 26 m it was west 4' ; after 

 this there was an easterly motion, changing again to west, which reached an extreme value at 23 h 44 m 

 of 17 divisions or 8' W. From the commencement of the horizontal force observations (17 h 38 m ) the 

 force was less than the normal ; at 20 h 4 m the greatest depression was 0.003 (parts of the force). The 

 disturbance continued till 6 A. M., the force being less than the standard value. From 17 h 38 m , when 



