XXVI 



General Results of the Makerstoun Observations. 



41. If we consider the mean position as deduced from all the observations in each month, we find that the 

 number of observations for which the declination was to the west, is least from 6*^ a.m. to lO'' a.m., and greatest 

 from 6"^ P.M. to lO*' P.M. ; the reverse of course holding for the deviations to the east : if, however, we consider 

 the hourly mean position deduced from the days selected free from disturbance, we find that the number of 

 westerly observations is greatest from about 9^ a.m. till noon, and that it is least from 8*^ p.m. till l'^ a.m. ; which 

 result is nearly the reverse of the other. As the maximum efiect of disturbance, in increasing the westerly 

 declination (No. 36), occurs about the same time as the maximum frequency of westerly excursions from the 

 undisturbed position (as seen in the second result), the displacement westerly of the mean position, by dis- 

 turbance, reduces the number of westerly excursions from that position to a minimum (as seen in the first 

 result). The same explanation applies to the other epoch. 



Diurnal Variation of the Sums of Disturbances of the Hourly values of Magnetic Declination in 1844 and 

 1845. — The following table contains the sums, for 100 observations, of the deviations of the north end of the 

 declination magnet from the monthly mean positions at the corresponding hours, the latter being deduced from 

 the days selected as free from irregular disturbance. 



Table 17. — Hourly sums, for 100 Observations of "Westerly Declination in 1844 and 1845, of the 

 Positive and Negative Excursions ft-om the Approximate Normal Positions for each Hour. 







Positive 



[W.) Disturbances. 







Negativ* 



! (E.) Disturbances. 





Mak. 























Mean 



Nov. 



Feb. 



May. 



Aug. 





Nov. 



Feb. 



May. 



Aug. 





Time. 



Dec. 



March. 



June. 



Sept. 



Year. 



Dec. 



March. 



June. 



Sept. 



Year. 





Jan. 



April. 



July. 



Oct. 





Jan. 



April. 



July. 



Oct. 





h, m. 



12 10 



77 



138 



73 



101 



97 



272 



305 



259 



339 



294 



13 10 



87 



144 



73 



107 



102 



277 



300 



253 



313 



286 



14 10 



114 



159 



88 



157 



129 



198 



264 



215 



270 



237 



15 10 



135 



146 



135 



177 



148 



178 



208 



159 



225 



193 



16 10 



128 



190 



138 



141 



149 



147 



171 



172 



190 



170 



17 10 



109 



167 



157 



225 



164 



123 



110 



134 



135 



126 



18 10 



178 



189 



176 



286 



207 



69 



72 



116 



83 



85 



19 10 



209 



203 



164 



294 



218 



43 



55 



118 



78 



74 



20 10 



236 



218 



216 



344 



254 



38 



69 



80 



48 



59 



21 10 



275 



258 



252 



335 



281 



40 



56 



77 



73 



62 



22 10 



249 



230 



261 



260 



251 



51 



59 



66 



92 



67 



23 10 



217 



206 



243 



260 



232 



66 



72 



98 



67 



76 



10 



294 



241 



219 



250 



251 



55 



79 



88 



67 



73 



1 10 



288 



250 



224 



250 



253 



72 



66 



99 



94 



83 



2 10 



279 



257 



219 



268 



256 



64 



77 



81 



91 



78 



3 10 



260 



243 



188 



244 



234 



112 



91 



109 



131 



111 



4 10 



233 



213 



159 



197 



201 



122 



93 



108 



109 



108 



5 10 



160 



149 



95 



157 



141 



150 



212 



113 



127 



150 



6 10 



159 



108 



71 



123 



116 



294 



309 



125 



251 



244 



7 10 



97 



108 



56 



97 



89 



274 



292 



168 



240 



243 



8 10 



62 



95 



40 



70 



67 



382 



304 



194 



364 



311 



9 10 



76 



120 



42 



52 



72 



303 



348 



170 



399 



305 



10 10 



77 



101 



48 



62 



72 



345 



312 



158 



393 



302 



11 10 



52 



94 



45 



87 



70 



374 



311 



220 



355 



315 



42. The results from the Table are as follows : — 

 \st. The sum of positive or westerly disturbances 



In Nov. Dec. Jan. 



Is a maximum at Qi^ Noon. 

 Is a minimum at 11^ p.m. 



Feb. March, April. 

 9^ A.M. and 2^ p.m. 



8'' P.M. — U'' P.M. 



May, June, July. 

 IQh A.M. 

 8^'^ P.M. 



Aug. Sept. Oct. 

 Sill A.M. 



9^^ P.M. 



2d, The sum of negative or easterly disturbances 

 Is a maximum at S'^ — 11^ p.m. 9*^ p.m. 



Is a minimum at 8** a.m. 



7'' a.m. 10*" A.M. 



12it A.M. 



IQi" 



A.M. 



91" P.M. 



8'' A.M.— Ol" Noon. 



