XXXVl 



General Results or the Makerstoun Observations. 



The conclusion deduced from the numbers for 1844, and which has been deduced from those for the magnetic 

 declination, No. 16, is also to be obtained from the numbers for 1845, thoiigh with less distinctness, owing to 

 the large effect of disturbance in January and December of the latter year (See No, 16.) In the mean of both 

 years March and April shew the greatest mean difference in the first six months (and for the whole year), and 

 August and December the greatest in the second six months : the least values are those for June and July, and 

 for January and February. 



64. From this result, June and July appear the months best fitted for observations of the horizontal com- 

 ponent of magnetic force ; the probable error of an observation from the mean for the corresponding hour in 

 these months being imder 0-0003 of the whole horizontal force. 



65. Annual Variation of the Number of Observations ivhich were greater than the Mordhly Means for the 

 corresponding Hour. — The numbers of observations in 100 which were greater than the monthly means for 

 each month of the years 1844 and 1845 are as follow : — 





Jan. 



Feb. 



March. 



April. 



:\[ay. 



.June. 



July. 



Aug. 



Sept. 



Oct. 



Nov. 



Dec. 



Mean. 



1844, 



53-1 



54-8 



60-1 



52-1 



52-5 



45-7 



47-1 



49-8 



54-3 



61-2 



55-6 



59-6 



53-8 



1845, 



59-6 



56-8 



56-9 



55-0 



53-2 



48-3 



50-8 



530 



53-0 



56-2 



56-3 



57-3 



54-7 



Mean, 



56-3 



55-8 



58-5 



53-5 



52-8 



47-0 



48-9 



51-4 



53-6 



58-7 



55-9 



58-4 



54-2 



From these numbers it appears, that in the year there are, in 100 observations, upwards of 8 more in 

 excess than in defect of the monthly means for the corresponding hour ; that June and July were the only 

 months which shewed more observations less than there were greater than the monthly means ; that in March, 

 October, and December, the number of observations in excess of the monthly means was greatest, being 17 in 

 100 more than those in defect. Upon the whole it appears probable in this, as in the other cases, that the 

 numbers for 1844 exhibit the mean annual law with greatest truth, and that the number of positive observa- 

 tions is least at the summer solstice, and is greatest near the equinoxes. 



Monthly Variations for the Horizontal Component. 



Table 28. — Mean Variations of the Horizontal Component of Magnetic Force, free from Regular 

 Secular Change, with reference to the Moon's Age and Declination. 















After 













Moon's 













Moon 













Age. 



1843. 



1844. 



1845. 



1846. 



Mean. 



farthest 



1843. 



1844. 



1845. 



1846. 



Mean. 















North. 



1 









000 



d. d. 



0-00 



0-00 



0-00 



o-ou 



0-00 



d. d. 



0-00 



It- 00 



0-00 



(J-OO 



14—16 



-0113 



-0229 



+ 0015 



-0005 



-0083 



27— 1 



1 + 0059 



+ 0121 



+ 0078 



-0019 



+ 0060 



17—20 



-0021 



-0250 



-0065 



-0139 



-0119 



2— 5 



- 0064 



+ 0008 



-0048 



+ 0076 



-0007 



21—24 



+ 0090 S-0001 



-0042 



-0072 



-0006 



6— 8 



1-0070 



-0127 



-0154 



+ 0037 



-0078 



25—28 



4-0142 +0203 



+ 0085 



+ 0088 



+ 0129 



9—12 



+ 0026 



+ 0012 



-0034 



-0060 



-0014 



29— 1 



+ 0043 



+ 0224 



+ 0040 



+ 0120 



+ 0107 



13—15 



+ 0041 



+ 0157 



+ 0093 



-0048 



+ 0061 



2— 5 



+ 0112 



+ 0221 



-0047 



+ 0049 



+ 0084 



16—19 



-0029 



+ 0106 



-0064 



+ 0065 



+ 0019 



6— 9 



-0074 



+ 0095 



-0068 



+ 0039 



-0002 



20—22 



+ 0034 



-0092 



+ 0035 



+ 0013 , 



-0002 



10—13 



-0179 



-0259 



+ 0084 



-0079 



-0108 



23—26 



0000 



-0186 



+ 0094 



-0062 



-0038 



66. Variations of the Daily Mean Horizontal Component with reference to the Moon's Age and Declination. 

 — Table 28 has been formed from the detailed Tables in former volumes, and from the Tables pp. 1 1 and 32 of 

 this volume. From the means in Table 28 we conclude : — 



1st, That the mean horizontal component is greatest about the time of conjunction, and least about oppo- 

 sition, or immediately before and after that epoch. This result is shewn with great distinctness in several single 

 lunations in 1844, (see volume for 1844, p. 358 and Plate XIV). 



2d, That the mean horizontal component is a maximum, both when the moon is farthest north, and when 

 it is farthest south, and that it is a minimum when the moon is near the equator. This result is shewn with 

 considerable distinctness in the variations for both 1844 and 1845 and with some irregularity in 1843 and 

 1846 ; the less value of conclusions from the observations of the two latter years should always be borne in mind. 



t 



