XXIV 



Geneeal Results of the Makerstoun Observations. 



38. Diurnal Variation of the Effect of Disturbance on the Mean Declination. — When we deduce the 

 yearly mean declination from the days selected as free from intermittent disturbance (No. 35.) we obtain the 

 following results : — 



Mean Declination from all the hourly observations in 1844, = 25° 17''06, 



from the hourly observations in the selected 120 days of 1844, = 25° 17''08 



60 =25° 17'-06 



„ 84 days of 



1845, =25° ll'-32 



1845, =25° ir-39 



The effect of disturbances, therefore, on the yearly mean position may be considered zero. When we compare 

 the monthly means, as deduced from the 10 days selected in each month of 1844 and the 7 days selected in 

 each month of 1845, with those deduced from all the hourly observations, we find that the average difference 

 (independent of sign) for the monthly means in these two years is about 0'-2 ; a difference which may be referred 

 with more probability to the effects of regular laws, or the fewness of the observations, than to the effect of 

 intermittent disturbance, which is zero on the yearly mean. It is evident, therefore, that, for the purpose of 

 the present discussion, we may assume, with little probable error, that the monthly mean from both series has 

 the same value (as in Tables 13 and 14), and take the differences of the hourly means in the two series as 

 measures of the effect of disturbance ; any possible error in this assumption can affect the values of the dif- 

 ferences but slightly ; the epochs of the maximum and minimum would still remain unaltered. In this man- 

 ner the following Table has been formed : — 



Table 15. — Differences of Disturbed and Undisturbed Diurnal Variations of "Westerly Declination, 

 as deduced from Tables 13 and 14, exhibiting the effect of Irregular Disturbance on the Hourly 

 Mean Positions. 



Mak. 

 Mean 



Dec. 

 Jan. 



March, 



May. 



July. 



Sept. 

 Oct. 



Sept. 

 to 



March 

 to 



Year. 



Time. 



Feb. 



April. 



June. 



Aug. 



Nov. 



Feb. 



Aug. 





h. m. 



12 10 



-1-06 



-0-65 



-0-95 



-0-77 



-103 



-1-05 



-0-79 



-0-92 



1.3 10 



-0-83 



-0-82 



-0-83 



-0-73 



-0-91 



-0-87 



-0-80 



- 0-83 



14 10 



-0-55 



-0-59 



-0-52 



-0-57 



-0-34 



-0-44 



-0-56 



-0-50 



15 10 



-0-23 



-0-51 



-0-43 



000 



-0-23 



-0-23 



-0-32 



-0-27 



16 10 



000 



+ 007 



-0-29 



-0-19 



-013 



-006 



-014 



-0-09 



17 10 



-013 



+ 0-21 



+ 0-06 



+ 0-52 



+ 0-29 



+ 008 



+ 0-26 



+ 0-18 



18 10 



+ 0-44 



+ 0-46 



+ 001 



+ 0-98 



+ 1-05 



+ 0-74 



+ 0-48 



+ 0-62 



19 10 



+ 0-55 



+ 0-77 



+ 0-11 



+ 0-95 



+ 1-23 



+ 0-89 



+ 0-61 



+ 0-76 



20 10 



+ 0-52 



+ 0-81 



+ 0-52 



+ 109 



+ 1-30 



+ 0-91 



+ 0-81 



+ 0-86 



21 10 



+ 0-66 



+ 105 



+ 0-62 



+ 0-58 



+ M2 



+ 0-89 



+ 0-75 



+ 0-82 



22 10 



+ 0-72 



+ 0-84 



+ 0-57 



+ 0-21 



+ 0-85 



+ 0-78 



+ 0-54 



i +0-66 



23 10 



+ 0-69 



+ 0-86 



+ 0-41 



+ 019 



+ 0-77 



+ 0-73 



+ 0-49 



+ 0-60 



10. 



+ 0-86 



+ 0-90 



+ 0-43 



+ 0-40 



+ 0-80 



+ 0-83 



+ 0-58 



+ 0-70 



1 10 



+ 1-08 



+ 1-08 



+ 0-76 



+ 0-49 



+ 0-65 



+ 0-86 



+ 0-77 



+ 0-81 



2 10 



+ M0 



+ 0-83 



+ 0-81 



+ 0-52 



+ 1-07 



+ 1-08 



+ 0-72 



i +0-90 



3 10 



+ 0-77 



+ 0-75 



+ 0-56 



+ 0-56 



+ 0-95 



+ 0-86 



+ 0-63 



+ 0-74 



4 10 



+ 0-86 



+ 0-77 



+ 0-60 



+ 0-48 



+ 0-49 



+ 0-67 



+ 0-61 



+ 0-64 



5 10 



+ 0-19 



-0-26 



+ 0-35 



+ 0-21 



+ 017 



+ 0-18 



+ 010 



+ 0-24 



6 10 



-0-41 



-101 



+ 0-16 



-0-47 



-0-89 



-0-64 



-0-44 



-0-54 



7 10 



-0-58 



-1-20 



-015 



-0-63 



-1-07 



-0-82 



-0-66 



-0-74 



8 10 



-1-37 



-105 



-0-53 



-0-71 



-1-77 



-1-57 



-0-77 



i -117 



9 10 



-1-17 



-1-08 



-0-70 



-1-38 



-1-28 



-1-22 



-1-05 



-MS 



10 10 



-1-08 



-103 



-0-67 



-1-21 



-1-55 



-1-31 



-0-97 



-1-14 



11 10 



-1-21 



-1.19 



-0-93 



-0-69 



-1-54 



-1-37 



-0-94 



-1-15 



39. The conclusions from this Table are, — 



\st. That the greatest effect of disturbance in increasing the westerly declination occurs 



In 



Dec. Jan. Feb. 



March, April. 



May, June. 



July, Aug. 



Sept. Oct. Nov. 



About 



Ih 40m P.M. 



9*^ A.M. to 1'^ P.M. 



Ih 40m P.M. 



8^ A.M. 



8^ A.M. 



