J A. D. Bache on the Horizontal 



of Magnetic F 



nth recorded; for January, 1841, the 

 , for June, 1841, the total number is 18. i 

 1843, January, February and March, the mean total number of 

 disturbances as found in the same months in the preceding and 

 following year was substituted, this mertn gave 8, 20, and 20 res- 

 pectively ; the number of disturbances after October, 1843 were 

 halved to make them comparable with the bi-hourly senes. 

 There were two anomalous months, July and December, 1840, iQ 

 which the disturbances amount to 165 and 120 with an annual 

 mean of 64, whereas in the same months in the following year 

 they amount to only 26, and 26 respectively, with an annual 

 mean of 27. The mean annual difference 37 was applied to the 

 numbers found in 1841, which gives 63, and 63 as a substiUUe 

 for the anomalous values in July and December, 1840. Toe 

 anomaly does not exist in the phenomenon itself, but is unques- 

 tionably due to the irregularity in the progressive change. 



Table No. IX, contains the number of disturbances as distnb- 

 uted over the several years and months ; all referred to a uni- 

 form series of bi-hourly observations. To this table the monthly 

 means and their ratio, when compared with the annual mean, 

 have been added ; also, for comparison, the corresponding ratioa 

 found in part I. of the discussion of the disturbances of the 



MONTH 



"r~ 



~w 



isr 



!^? 1^1 



-^ 





-ml 



i--. 



,,, 



44 





26 





68 















tis 





49 





i5 











z-::^- 



<S' 



26 



5 





"\ 



f^ 



o:S 



0-68 



itr- 



5o 



V. 



20 





9 



li 



IS 





48 















"^i 



± 





i6 



1 





11 



-V 



u^ 



^l 



Sums. 



-J- 







~6~ 



-T3- 



Mean. 



.8 



20 



__ 



In the columns of ratios the principal maxima and minima ai« 

 indicated by an asterisk. 



The annual means exhibit plainly the eleven year inequalityr 

 tiiey have been represented by the formula: 



N« 4-14-4- 10-2 (f-1848) +4-8 (f-1843)^ 

 j Janoaiy, 1841 52 ; 54 j 



