154 ABSTRACTS FOR THE MaGNnetic Dr. 
TABLE XXV.—Monthly Means of Macnetic Dip, from Observations of Needle No. 1. 
Magnetic Dip. 
Num 
Month. Ce ee : From Three Months. 
NET P.M. ans Sp ss A. = aia 
A.M. | P.M. A.M. P.M, Mean, |“ eee 
1841. take ee reh Z 71° (Ae file 
September | 1 | 2 | 71 14-19 | 71 1418 | 71 1418 | +001) | , ; : , 
October 4 4 71 18-67 | 71 14-14 | 71 16-40 + 4:53> | 15-00 13-79 14-39 + 1-21 
November 5 4 71 12-23 | 71 13-25 | 71 12-74 1-02 
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 — 0-51 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 14-50 + FA 
May | 4 3 71 12-03 | 71 12-92 | 71 12-47 — 0-89 13-35 12-32 12-83 + 1-03 
June 4 4 71 12-45 | 71 10-47 | 71 11-46 _ 0-024 
July 3 5 71 14-60 | 71 13-20 | 71 13-90 + 1-40) 
August 5 71 13-81 71 13-452 13-70 12.98 13-34 + 0-72 
September | 4 5 | 71 12-87 | 71 12-75 | 71 12-81 + 0-12 
October 5 3 71 10-57 | 71 11-12 | 71 10-84 — 0-55 
November 3 3) 71 9-13 | 71 6-60 | 71 7-86 + 2-53 9-77 9.08 9-42 | + 0-69 
December 4 2 79:25 "7 19-50) | 7a (9-37 — 0-25 
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 cirele. 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 Noy. 1842, gives Ad = —3°59. 
Taba aebaea haarneceetae ret ssisewacate aeaeen Seacies Oct., Nov., and Dec. 1842, ......... =—4:59. 
OctwandsNoy. S455 0 Pesce. seen: Oct wand Nov 822.95) eases =—522. 
AMES Sree oi RT a RE 9 iE at ol Noy. and Dee. 1842, deaueeeee = Doe 
Mean of all = — 483. 
In all cases, the means of all the observations in the given period has been used, and not the mean of tho 
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 quarterly 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. 
Magnetic Dip. 
Period. 
Mean. A.M. minus P.M, 
1842. ‘ ‘ 
First Six Months 12-39 + 0-45 
Last Six Months 11-47 + 0-51 
First and Last Quarters 10-64 + 0-22 
Second and Third Quarters 2-6 13-08 + 0-87 
The Year 11-95 + 0-42 
Twelve Months of 1842 wan fae 
Three Months of 1841 rom 
