Ixx 



General Results of the Makeestoun Observations. 



Table 66. — Variations of the Total Magnetic Force with reference to the Moon's Hour-Angle for 

 the Winter and Summer Lunations, and for all the Lunations of the Years 1844 and 1845. 



Moon's 

 Hour- 



Winter Lunations. 



Summer Lunations. 



All the Lunations. 





















Angle. 



1844. 



1845. 



Mean. 



1844. 



1845. 



Mean. 



1844. 



1845. 



Mean. 



h. m. 



0-000 



0-000 



O-OllO 



0-000 



0-000 



0-000 



0-000 



0-000 



* 0-000 







-055 



000 



-028 



+ 018 



+ 011 



+ 015 



-019 



+ 006 



; -007 



2 25 



-091 



+ 025 



-032 



-006 



+ 030 



+ 012 



-048 



+ 028 



! -010 



4 20 



-068 



-046 



-057 



-Oil 



+ 020 



+ 005 



-040 



-015 



' -027 



6 15 



-068 



-031 



-050 



-023 



+ 001 



-Oil 



-045 



-015 



-030 



8 10 



-052 



-039 



-045 



-034 



-036 



-035 



-043 



-037 



-040 



10 5 



-010 



000 



-005 



-009 



+ 002 



-004 



-010 



+ 001 



-004 



12 



+ 066 



+ 030 



+ 048 



-007 



+ 020 



+ 006 



+ 029 



+ 025 



+ 027 



13 55 



+ 106 



+ 042 



, +073 



+ 023 



+ 027 



+ 024 



+ 065 



+ 035 



+ 050 



15 50 



+ 084 



+ 045 



+ 065 



+ 038 



-003 



+ 017 



+ 062 



+ 023 



+ 042 



17 45 



+ 054 



+ 024 



+ 039 



+ 010 



-028 



-009 



+ 031 



000 



+ 015 



19 40 



+ 045 



-015 



+ 015 



-007 



-039 



-022 



+ 019 



-026 



, -004 



21 35 



-006 



i 



-031 



-018 



+ 008 



-006 



000 



+ 001 



-019 



1 -008 



146, Variation of the Total Magnetic Force with Reference to the Moon^s Hour- Angle. — Of the four indepen- 

 dent results in Table 66, that for the winter lunations of 1844 has the greatest range, and only one maximum 

 and minimum, the maximum occurring about 2 hours after the moon's inferior transit, and the minimum about 

 2 J hours after the superior transit : the three other results shew two maxima and two minima as follow : 



A maximum from 2 to 4 hours after the moon's inferior transit. 

 A minimum from 4 to 2^ hours before the moon's superior transit. 

 A maximum from to 2J hours after the moon's superior transit. 

 A minimum from 6 to 8 hours after the moon's superior transit. 



In the mean of all, as shewn in the last column of Table 66, the first minimum and second maximum noted above, 

 are scarcely visible, owing to the effect of the great range of the exceptional result for the winter lunations of 

 1844. The epochs from the means of all are — 



The maximum of total force 2f hours after the moon's inferior transit. 



A minimum 2 hours before 



A maximum near 



The minimum 8 hours after 



superior transit, 

 superior transit, 

 superior transit. 



It is probable that the mean of all the lunations is vitiated by the winter lunations of 1844, and that the 

 epochs given above for the remaining lunations of the two years are near the truth. 



Combined Motions of the Magnetic Needle. 



147. Motions of the North End of a Magnetic Needle sufposed freely suspended in the direction of the Magnetic 

 Force. — These motions have been represented in Plates VI.— VIII. by projecting the variations of dip, given in 

 the previous Tables, as ordinates to the abscissae deduced from the variations of declination for the same epochs 

 multiplied by the cosine of the dip ( = 0-32). As great care has been bestowed on the determination and veri- 

 fication of the coefficients of reduction for the bifilar and balance magnetometers, upon which the element of 

 dip depends, it is conceived that considerable confidence may be placed in the accuracy of these figures as re- 

 presentatives of the motions of the north end of a needle supposed freely suspended in the direction of dip at 

 Makerstoun. No attempt has been made in these discussions to introduce theoretical views, but a consideration 

 of the figTires in the Plates will probably show the futility of many of the theories brought forth to explain the 

 motion in declination. 



148. Annual Motions. — The annual motion deduced from the observations of the three magnetometers for the 

 four years 1843-6 is shown in figure A, Plate VI. In order to exhibit a more symmetrical form of the annual 



