dii 



General Results of the Makerstoun Observations. 



The hours for the months December to February are very uncertain, owing to the irregularity and smallness 

 of the variations. Throughout the year the effect of disturbance is zero about W^ a.m. and about 8^ p.m. 



Diurnal Variation of frequency of the Positive Departures from the Hourly Mean Positions. — The number 

 of observations having been obtained for each month in 1844 and 1845, which shewed a greater value of the 

 horizontal component than the monthly means at the corresponding hours, the means of quarterly groups were 

 formed, and the numbers per cent, are given in the following Table. 



Table 35. — Numbers of Observations of the Horizontal Component of Magnetic Force in 100, which 

 were greater than the Monthly Mean at the corresponding Hour in the Years 1844 and 1845, 

 for each Quarter, and for the Year. 



Mak. 



Nov. 



Feb. 



May. 



Aug. 





Mak. 



Nov. 



Feb. 



May. 



Aug. 





Mean 



Dec. 



March. 



June. 



Sept. 



Year. 



Mean 



Dec. 



March. 



June. 



Sept. 



Year. 



Time. 



Jan. 



April. 



July. 



Oct. 





Time. 



Jan. 



April. 



July. 



Oct. 





li. m. 



12 12 



6.3-3 



59-7 



49-4 



59-5 



58-0 



h. m. 



12 



52-5 



51-9 



50-6 



51-9 



51-7 



13 12 



62-0 



64-3 



50-6 



55-7 



58-1 



1 12 



52-5 



48-7 



51-3 



47-5 



50-0 



14 12 



65-8 



68-8 



50-0 



58-9 



60-9 



2 12 



55-7 



46-1 



46-2 



53-2 



50-3 



15 12 



60-8 



60-4 



50-6 



56-3 



570 



3 12 



55-7 



39-0 



47-5 



45-0 



46-8 



16 12 



55-7 



58-5 



56-3 



53-2 



55-9 



4 12 



63-3 



45-5 



46-2 



41-8 



49-2 



17 12 



57-0 



57-1 



54-4 



62-7 



57-8 



5 12 



57-6 



49-4 



51-9 



44-9 



50-9 



18 12 



50-6 



53-2 



51-3 



57-0 



530 



6 12 



48-1 



51-9 



44-9 



51-3 



490 



19 12 



51-9 



57-1 



48-7 



56-3 



53-5 



7 12 



59-5 



50-6 



46-8 



53-2 



52-5 



20 12 



51-9 



59-1 



48-7 



57-6 



54-3 



8 12 



55-7 



56-5 



42-4 



55-7 



52-6 



21 12 



55-7 



61-7 



51-3 



55-1 



55-9 



9 12 



58-2 



57-8 



45-6 



570 



54-6 



22 12 



56-3 



59-7 



51-3 



61-4 



57-2 



10 12 



65-2 



60-4 



48-7 



58-9 



58-3 



23 12 



54-4 



571 



48-1 



57-6 



54-3 



11 12 



59-5 



59-1 



52-5 



601 



57-8 



74. The following are the approximate epochs of maximum and minimum frequency of positive departures, 

 as deduced from Table 35. 





Nov. Dec. Jan. 



Feb. March, April. 



May, .June, July. 



Aug. Sept. Oct. 



Year. 



Maximum, 



V" A.M. 



2^ A.M. 



4*' A.M. 



ll^^ P.M. to IV" A.M. 



2^ A.M 



Minimum, 



1^ A.M. and l'^ P.M. 



S** P.M. 



B"* P.M. 



4^ P.M. 



3bp.M 



The numbers in Table 35 present considerable irregularities ; two years' observations appear too few to 

 remove these. In the winter and spring quarters, there is a secondary maximixm of frequency of positive de- 

 partures about 9I1 A.M., a secondary minimum occurring in the winter quarter about noon, and in the spring 

 quarter about &^ a.m. The variation of the numbers is gi'eatest in the spring and autumn quarters, it is least 

 in summer. Every hour in winter, with one exception, had more observations greater than the monthly mean 

 for the hour, than there were less ; in spring and autumn, all the hours had a greater number of positive than 

 of negative departures, excepting those from l"^ to 5i^ p.m. The minimum of positive frequency occurs 

 about 7** A.M. in winter, but in summer it occurs nearer 7*^ p.m. The hours of maximum frequency of the 

 positive departures, are obviously those of minimum frequency of negative departures. 



75. It may be remarked here, that these departures are from the mean position of all the ordinary observa- 

 tions, which mean position is more or less affected by disturbance ; could the undisturbed mean position be well 

 ascertained it would probably be found, as it has been in the case of the declination, No. 41, that the hour of 

 maximum frequency of the positive departures from the disturbed mean position, is nearly that of their mini- 

 mum frequency from the undisturbed mean position ; this, it will be seen, was the case when the selected days 

 wei-e assumed as the normal means, as in 1844. (See volume for 1844, page 372). 



76. Diurnal Variation of the Mean Differences of the Values of the Horizontal Component from the Monthly 

 Mean Values for the corresponding Hours. — Table 36 has been formed in the manner already indicated, No. 

 43, for Table 18. The numbers in Table 36 exhibit such considerable irregularities, that it is difficult in some 

 cases to determine real secondary points of maximum and minimum from those which may be merely accidental, 

 and which might have disappeared in the combination of a larger series of observations ; the following how- 

 ever, are the approximate epochs as nearly as they can be determined. 



L 



