28 APPENDIX. 



at these hours was 85 divisions (0.003 parts of the force) less than the normal amount. The vertical 

 force is apparently undisturbed; it is slightly above the normal value. 



III. 1S40, July 6th. An aurora was noticed at 0'' 25" and -2^ 25"". The declination was disturbed 

 nt C" igi" and 2*' lOi"; it indicated 50 divisions and 34 divisions, or 17' and 12' of easterly deflection. 

 It is likely that there were disturbances two hours preceding and two hours following the above times, 

 as the scale could not be read. The horizontal force was disturbed from midnight till 2 P. M. ; the 

 force was less during this time, and reached its minimum value at 2'' 22™ of 130 divisions or 0.005 

 parts of the force ; between 2 and 8 A. M. the diminution was about 0.004 parts. The vertical force 

 was also less from midnight till after 2^ 17"°, the greatest diminution probably took place later as the 

 observations failed at 4'' 17'". ^Minimum value at 2'' 17™, 0.004 parts of the force. 



lY. 1840, July 29th. At 22'' 25"" a faint aurora. The declination was not disturbed. The hori- 

 zontal force was very slightly affected. At 20'' 22'" it was 0.001 parts less than the normal, at 22'' 

 22"" it was nearly normal, and at O"" 22"" (30th) it was greater by 0.002. There may have been 

 ordinary disturbances not immediately connected with the aurora. At 22'' 17"° the vertical force was 

 slightly affected, the force decreased 0.002 parts below the normal. 



Y. 1840, August 19th. At 20'' 25™ auroral liglit in N ; 22'' 25"" aurora continues in N. and N. W. 

 The declination disturbance commenced at 22'' 20™ and continued to 2'' 20'" (20th), west deflection 48 

 divisions (22'), 10 divisions, and 10 divisions. The horizontal force was disturbed from 16'' 22™ to 

 22'' 22™, force less 43 divisions, 49, 102, and 85 divisions Tin minimo 0.004 parts of the force). The 

 vertical force seems lower than usual, but hardly reached the limit of a recognized disturbance. 



YI. 1840, August 28th and 29th. An aurora appeared at 20'' 39^™ in N. N. E., disappeared at 

 21'' 19i™, reviving at 21'' 59^™ ; at 22'' Oi"" streamers moving from E. to W. ; light continued in N.; 

 streamers again in N. E. at 22'' 595™ '^^^ 1'' ^-^i". ^fter which time the aurora was not observed. An 

 easterly movement of the needle commenced about 20'' 19™ with a maximum eastern deflection of 125 

 divisions (or 57') at 2^ 0°, the westerly motion continued til! 21'' 55™ when the needle was yet 5' 

 east of its normal position; smaller fluctuations were observed till midnight, the deflection was then 

 19' east; half an hour later it was 20' east; the morning extreme was reached at 1'' 35™, when the 

 deflection was 25' east ; after this the disturbance gradually subsided. There was a disturbance of 

 the horizontal force about 18** 20™ ; from about 21'' 52"" till 10 the next morning the horizontal force 

 remained below its normal value. At 23'' 32™ it was 0.009 (parts) below, at O*" 22™ it was 0.007, and 

 at 1'' 22™ its minimum value of 0.010 (parts of the force) was reached. The disturbance in the 

 vertical force appears to have commenced about 21'' 7™, when the force gradually decreased till 21'' 

 57™ when it reached a minimum of about 0.003 (parts) ; after this it gradually increased. 



YII. 1840, September 21st. At 20'' 25"' faint aurora, 22'' 25™ aurora disappeared. Disturbance 

 of the declination commenced at 20'' 20™ and continued to 4'' 20™ (22d), deflections 40 divisions (18') 

 W., 10 divisions E., 14 divisions W., and 23 divisions E. The horizontal force disturbance com- 

 menced at 16'' 22™ and ceased at 4'' 22™ next day ; force less 69 divisions, 47 divisions, 71 divisions, 

 42 divisions, 94 divisions, 124 divisions (0.005 parts of the force), and 93 divisions. The vertical 

 orce between 16'' and 23'' was slightly above the average, but suddenly became much smaller than the 

 normal between midnight and 3 A. M. Minimum about 0.002 parts of the force. 



YIII. 1842, April 14th. At 22'' 40™ appearance of aurora, a bright light in the N. ; at 0" 20™ 

 (15th) an arc of light was visible extending to about 15° above the north horizon. Declination dis- 

 turbed from 22'' 20™ to 8'' 20™ (15th), deflections at the regular observing hours 23 divisions W., 39 

 E., 11, 37, 10, and 14 divisions W. Maximum west deflection at 22'' 56™, 58 divisions (26'), maxi- 

 mum east deflection 39 divisions (18'), derived from the series of extra observations. The horizontal 

 force disturbances commenced at 22'' 22™ and ceased at 4'' 22™, force less 39 divisions, 149 divisions, 

 37 divisions, and 50 divisions, minimum 279 divisions (0.010 parts of the force) at l*" 16™ (15th). 

 But one of the 69 extra readings during this aurora shows an increase of force. The vertical force 



