ABSTRACTS FOR THE MAGNETIC Dip. 155 
_ TABLE XXVII.—Monthly Mean Values of A 4, the Differences of Magnetic Dip, for the Observation Hours of 
} é 1842, deduced from Tables X. and XVIII. ; the value of A é@ December 2 being taken as Zero, 
Month. | 20, | aa, | as Se ee wan. |e 
January 6-11 6-62 5:56 5-71 6-00 1-06 5-91 0-40 
February 6-04. 6-51 5-63 5-16 5-83 1-35 5-60 0-88 
March 5-18 5-99 4-51 4-01 4-92 1-98 4-59 1-17 
April 5-59 6-17 4-61 3-56 4-98 2.61 4-57 2-03 
May 4-62 5-12 3:39 3-26 4.10 1-86 3-94 1-36 
June 4-34 4-84 2-95 2.06 3-55 2-78 3.20 2.28 
July 4-22 4.42 2-40 2.05 3-27. || 2-37 3-13 2-17 
August 3-83 4-45 2.28 1-73 3-07 2-72 2.78 2-10 
September 2-88 3-83 2.21 1.99 2.73 1-84 2-43 0-89 
- October 1-64 2.47 1-38 1-44 1-73 1-03 1-54 0-20 
November 1-15 1-60 0-97 0-95 1-17 0.65 1-05 0-20 
December 0-22 0-15 0-16 
The Table above was computed from the formula 
AY AX } 
piiaiee = ea 
AY 
—y was obtained from Table X., sid 2 "trom Table XVIII. ; # being taken at 71° 18’. 
The following Table has been formed from oo above. 
‘TABLE XXVIII.—Mean Values of A é for Three Months, for the Summer and Winter Months, and for the 
Year 1842. 
Period. 20h, 23h, Qh, 5h, Mean of the Range. Mean of Difference of 
Four Hours, 20% and 54, || 20% and 5%, 
1842. 
- Jan., Feb., March 5-78 6.37 5-23 4-96 5-58 1-41 5:37 0-82 
| April, May, June 4-85 5:38 3-65 2-96 4-21 2-42 3-90 1-89 
July, Aug., Sept. 3-64 4-23 2-30 1-92 3-02 2:31 2-78 1-72 
Oct., Nov., Dec. 1-01 1-56 0-78 0-82 1-04 0-78 0-91 0-19 
Jan., Feb., March 
Oct.. Nov., Dee. t 3-39 3:96 3-00 2-89 3-31 1:07 3-14 0-50 
April, May, June, 3 : , 
| July, Aug., Sept. 4-24 4-80 2-97 2-44 3-61 2-36 3-34 1-80 
| The Year 3-82 4-38 2-99 2-66 3:46 1-72 3-24 1-16 
The columns containing the means and differences of 20" and 5" have been given for comparison with the 
Magnetic Dip, obtained from the Inclinometer at these hours. 
The winter months indicate a maximum Dip about 23", and a minimum between 2" and 5%, apparently 
nearer 5° than 2h in the first quarter of 1842, but nearer 2 than 5 in the last quarter. The maximum seems 
to occur somewhat earlier, and the minimum inter a in the summer than in the winter months. 
} The ratio of the difference of Dip at 20" and 55 in winter to that in summer is nearly the same from both 
_ Tables XXVI. and XXVIIL., though the quantities arerather different. 
The annual diminution of Dip cen Table XXVII. appears greater than that from the: observation of the- 
‘Inclinometer. 
