154 



Absteacts foe the Magnetic Dip. 



TABLE 



XXV 



. — Monthly 



Means of Magnetic Dip, 



from Observations of Needle No. 1. 





Month. 



Magnetic Dip. 



Number of 

 Observations. 



A.M. 



P. M. 



Mean of a.m. 

 and P. M. 



A.M. minus 

 P.M. 



From Three Months. 



A.M. 



P.M. 



A. M. 



P.M. 



Mean. 



A. M. minus 



P.M. 



1841. 







o , 





' 



o , 



' 



71' 



71° 



71° 





September 



1 



2 



71 14-19 



71 



14-18 



71 14-18 



+ 001) 

 + 4-53y 

 - 1-02) 











October 



4 



4 



71 18-67 



71 



14-14 



71 16-40 



15-00 



13-79 



14-39 



+ 1-21 



November 



5 



4 



71 12-23 



71 



13-25 



71 12-74 











December 





1 





71 



11-31 















1842. 

























January 



3 



2 



71 9-94 



71 



10-66 



71 10-30 



- 0-72) 











February 



3 



4 



71 13-53 



71 



14-04 



71 13-88 



- 0-51V 



11-74 



11-99 



11-86 



- 0-25 



March 



4 



4 



71 11-75 



71 



10-61 



71 11-18 



+ 1-14| 











April 



4 



5 



71 15-58 



71 



13-43 



71 1450 



+ 2-15) 











May 



4 



3 



71 1203 



71 



12-92 



71 12-47 



- 0-89y 



13-35 



12-32 



12-83 



+ 1-03 



June 



4 



4 



71 12-45 



71 



10-47 



71 11-46 



- 02) 











July 



3 



5 



71 14-60 



71 



13-20 



71 13-90 



+ 1-40) 











August 



5 





71 13-81 







71 13-45? 



+ 0-12f 



13-70 



12-98 



13-34 



+ 0-72 



September 



4 



5 



71 12-87 



71 



12-75 



71 12-81 











October 



5 



3 



71 10-57 



71 



11-12 



71 10-84 



- 0-55) 











November 



! 3 



3 



71 913 



71 



6-60 



71 7-86 



+ 2-53V 



9-77 



9-08 



9-42 



+ 0-69 



December 



4 



2 



71 9-25 



71 



9-50 



71 9 37 



- 0-25J 











The above Table has been formed by subtracting 12' from the means of the original observations, as a correc- 

 tion for the axle and copper circle. The a.m. observations were made between 20'^ and 21'* ; the p.m. observations 

 about 6'\ 



The diminution of Dip in 12 months has been deduced from four comparisons, as under : — 



Sept., Oct., and Nov. 1841, compared with Sept., Oct., and Nov. 1842, gives A^ = —3-59. 



Oct., Nov., and Dec. 1842, =-459. 



Oct. and Nov. 1841, Oct. and Nov. 1842, =-522. 



Nov. and Dec. 1842, =-5-9I. 



Mean of all =-4'- 83. 

 In all cases, the means of all the obsei'vations in the given period has been used, and not the mean of the 

 monthly means for the period. 



With the exception of the first quarter of 1842, the quarterly means give the Dip greater in the morning 

 than in the evening; giving the quai'terly differences a.m. minus p.m. equal values the mean of the whole is 0''68. 

 The observations of 1842 evince a greater difference in summer than in winter. 



TABLE XXVI. — ^Mean Magnetic Dip for periods of Six Months, and for the Year 1842. 



Period. 



Magnetic Dip. 



A.M. 



P.M. 



Mean. 



A.M. mintis P.M. 



1842. 

 First Six Months 

 Last Six Months 

 First and Last Quarters 

 Second and Third Quarters 

 The Year 



Three Months of 1841 and) 

 Twelve Months of 1842 / 



O / 



71 12-62 

 71 11-73 

 71 10-75 

 71 13-52 

 71 1216 



71 12-66 



71 12-17 

 71 11-22 

 71 10-53 

 71 12-65 

 71 11-74 



.71 12-15 



71 12-39 

 71 1147 

 71 10-64 

 71 13-08 

 71 11-95 



71 12-40 



+ 0-45 

 + 0-51 

 + 0-22 

 + 0-87 

 + 0-42 



+ 0-5] 



