Ivi 



General Results of the Makerstoun Observations. 



Table 53. — Mean Difference of the Observations of the Vertical Component of Magnetic Force, 

 in 1844 and 1845, from the Monthly Means at the corresponding Hours in each Year, as deduced 

 from all the Regular Observations. 



Mak. 

 Mean 

 Time. 



Mean Positive Differen 



:e. 



Mean Negative Difference. 



Mean Difference. 



Nov. 

 Dec. 

 Jan. 



Feb. 

 Mar. 

 April. 



May. 

 June. 

 July. 



Aug. 

 Sept. 

 Oct. 



Year. 



Nov. 

 Dec. 

 Jan. 



Feb. 

 Mar. 

 April. 



May. 

 June. 

 July. 



Aug. 

 Sept. 

 Oct. 



Year. 



Nov. 

 Dec. 

 Jan. 



Feb. 

 Mar. 

 April. 



May. Aug. 

 June. Sept. 

 July. Oct. 



Year. 



h. m. 



12 13 



0-00 



0159 



0-00 



0229 



000 



0151 



000 



0187 



0-00 



0183 



0-00 



0199 



O'OO 



0533 



0-00 



0208 



0-00 



0379 



0-00 



0311 



0-00 



0177 



0-00 



0320 



0-00 



0175 



0-00 



0250 



0-00 



0230 



1.3 1.3 



0147 



0222 



0183 



0187 



0185 



0191 0431 



0252 



0379 



0303 



0166 



0293 



0212 



0250 



0230 



14 13 



0138 



0226 



0173 



0197 



0185 



0259 0567 



0283 



0400 



0352 



0171 



0323 



0215 



0264 



0243 



15 13 



0142 



0203 



0180 



0206 



0184 



0196 0497 



0293 



0409 



0334 



0165 



0288 



0223 



0274 



0237 



16 13 



0136 



0185 



0151 



0214 



0172 



0195 0487 



0263 



0389 



0320 



0160 



0268 



0192 



0276 



0224 



17 13 



0139 



0173 



0145 



0181 



0161 



0185 



0403 



0237 



0351 



0281 



0159 



0242 



0180 



0239 



0205 



18 13 



0135 



0148 



0140 



0153 



0144 



0179 



0274 



0201 



0304 



0236 



0154 



0192 



0165 



0204 



0179 



19 13 



0134 



0124 



0134 



0143 



0134 



0151 



0171 



0167 



0198 



0170 



0142 



0144 



0149 



0166 



0150 



20 13 



0133 



0101 



0131 



0130 



0124 



0141 



0145 



0154 



0156 



0148 



0137 



0119 



0142 



0142 



0135 



21 13 



0125 



0097 



0121 



0120 



0116 



0147 



0126 



0160 



0122 



01.38 



0135 



0110 



0138 



0121 



0126 



22 13 



0120 



0101 



0122 



0111 



0113 



0141 



0112 



0137 



0120 



0128 



0130 



0106 



0129 



0115 



0120 



23 13 



0120 



0115 



0132 



0112 



0119 



0120 



0115 



0124 



0106 



0117 



0120 



0115 



0128 



0109 



0118 



13 



0137 



0157 



0123 



0163 



0145 



0122 



0131 



0121 



0111 



0121 



0129 



0143 



0122 



0132 



0132 



1 13 



0140 



0146 



0115 



0180 



0143 



0127 



0124 



0125 



0123 



0124 



0133 



0134 



0120 



0146 



0133 



2 13 



0163 



0174 



0113 



0183 



0156 



0123 



0132 



0135 



0133 



0130 



0140 



0150 



0123 



0154 



0142 



3 13 



0289 



0251 



0131 



0246 



0220 



0155 



0144 



0139 



0157 



0151 



0202 



0183 



0135 



0192 



0178 



4 13 



0333 



0260 



0166 



0282 



0254 



0179 



0140 



0147 



0180 



0162 



0233 



0182 



0156 



0220 



0198 



5 13 



0392 



0368 



0182 



0359 



0315 



0189 



0181 



0152 



0198 



0181 



0255 



0243 



0166 



0255 



0230 



6 13 



0447 



0341 



0164 



0285 



0292 



0187 



0188 



0151 



0157 



0171 



0264 



0242 



0157 0202 



0216 



7 13 



0336 



0227 



0152 



0213 



0225 



0168 



0142 



0130 



0148 



0147 



0222 



0175 



0140 0175 



0178 



8 13 



0209 



0153 



0124 



0131 



0151 



0131 



0128 



0122 



0131 



0129 



0161 



0139 



0123! 0131 



0139 



9 13 



0172 



0131 



0108 



0110 



0127 



0138 



0157 



0119 



0180 



0146 



0153 



0143 



0113 0137 



0136 



10 13 



0150 



0160 



0103 



0114 



0132 



0176 0246 



0121 



0189 



0179 



0162 



0194 



0111 0142 



0152 



11 13 



0150 



0150 



0115 



0148 



0142 



0199; 0273 



0137 



0322 



0222 



0171 



0194 



0125 0203 



0173 



105. The approximate epochs of maxima and minima for the mean positive and negative differences, the 

 principal being indicated by + and — , are as follow : — 



Jlean Positive Difference. 



Mean Negative Difference. 





Min. 



Max. 



Min. 



Max. 



Min. 



Max. 



Min. 



Max. 



Nov Dec .Jan 



-lOJ" A.M. 

 - 9i^ A.M. 



+ 6i^ P.M. 

 + 5J'' P.M. 







C" Noon 



.Sf* P.M. 

 6^ P.M. 



8i>> P.M. 

 8P P.M. 



+ 2i^ A.M 



+ 2i^ A.M 



Feb. Mar. April, 



gi" P.M. 



1'' A.M. 



-lOP A.M. 



May, June, July, 



2'' P.M. 



+ 51> P.M. 



-lOh P.M. 



+ 2'' A.M. 



- 0^ Noon. 



Sfll" P.M. 



-Qh P.M. 



+ 2|1' A.M 



Aug. Sept. Oct. 



-lOP A.M. 



+ 5'' P.M. 



- 9i^ P.M. 



•4'' A.M. 



-11J1> A.M. 



5'' P.M. 



8^ P.M. 



+ 3^ A.M 



106. The mean positive ditference has two maxima and two minima in each quarter excepting winter ; the 

 pi'incipal maximum occurs between b^ and 6*^ p.m. ; in summer the two maxima have an equal value ; the 

 values of the two minima differ little. 



107. The mean negative difference has two maxima and two minima in each quarter; the principal maxi- 

 mum occurs between 2'^ and 3^ a.m. ; in winter the two maxima differ little in value ; in the other quarters the 

 secondary maximum is very small compared with the other ; the values of the two minima in each quarter 

 differ little. 



108. It appears, therefore, that the principal maximum of the mean positive diffei'ence occui's at the same 

 time as the secondary maximum of the mean negative difference, and vice versa. It seems probable that if differ- 

 ences were taken with reference to mean undisturbed positions, the secondary maximum would disappear in 

 each case ; thus, if we consider that the effect of disturbance is to increase the mean vertical component to a 

 large extent about 6^ p.m. (No. 103, 1st), it is obvious that both the value and the number of the negative 

 departures from this increased mean will be greater than if the undisturbed mean were taken as the zero. It was 

 accordingly found in the discussion of the observations for 1844, (pp. 388, 389), when the mean position was 

 employed as deduced from the days selected nearly free from intermittent disturbance, that the maximum of 



