DiuENAL Variations for the Total Magnetic Force. 



Ixix 



Table 65. — Differences of Disturbed and Undisturbed Diurnal Variations of the Total Magnetic Force, 

 as deduced from Tables 63 and 64, exhibiting the effect of Irregular Disturbance on the Hourly 

 Mean Positions. 















Six Months. 





Mak. 

 Mean 

 Time. 



Dec. 

 Jan. 

 Feb. 



March. 

 April. 



May. 

 June. 



July. 

 Aug. 



Sept. 

 Oct. 



Nov. 



Sept. 



to 

 Feb. 



March 



to 

 Aug. 



Twelve 

 Months. 



h. m. 



0-00 



O'OO 



0-00 



0-00 



0-00 



0-00 



0-00 



0-00 



12 13 



-0075 



-0207 



-0092 



-0122 



-0129 



-0102 



-0140 



-0120 



13 13 



-0057 



-0206 



-0129 



-0143 



-0133 



-0095 



-0159 



-0128 



14 13 



-0094 



-0261 



-0146 



-0169 



-0149 



-0121 



-0192 



-0158 



15 13 



-0071 



-0184 



-0152 



-0170 



-0140 



-0105 



-0169 



-0138 



16 13 



-0054 



-0155 



-0135 



-0161 



-0137 



-0096 



-0150 



-0123 



17 13 



-0042 



-0121 



-0110 



-0158 



-0110 



-0076 



-0130 



-0103 



18 13 



-0023 



-0077 



-0071 



-0126 



-0073 



-0048 



-0091 



-0070 



19 13 



-0014 



-0055 



-0049 



-0090 



-0051 



-0033 



-0065 



-0049 



20 13 



-0016 



-0047 



-0039 



-0057 



-0022 



-0019 



-0048 



-0034 



21 13 



-0016 



-0031 



-0016 



-0033 



-0007 



-0011 



-0027 



-0020 



22 13 



-0014 



0000 



-0001 



-0019 



+ 0022 



+ 0004 



-0006 



-0002 



23 13 



+ 0006 



+ 0034 



+ 0021 



-0001 



+ 0030 



+ 0018 



+ 0018 



+ 0018 



13 



+ 0007 



+ 0079 



+ 0037 



+ 0028 



+ 0088 



+ 0047 



+ 0048 



+ 0048 



1 13 



+ 0016 



+ 0100 



+ 0045 



+ 0063 



+ 0100 



+ 0058 



+ 0069 



+ 0063 



2 13 



+ 0032 



+ 0135 



+ 0075 



+ 0093 



+ 0109 



+ 0070 



+ 0101 



+ 0086 



3 13 



+ 0062 



+ 0167 



+ 0103 



+ 0150 



+ 0159 



+ 0111 



+ 0140 



+ 0125 



4 13 



+ 0069 



+ 0192 



+ 0097 



+ 0204 



+ 0161 



+ 0115 



+ 0165 



+ 0139 



5 13 



+ 0083 



+ 0265 



+ 0157 



+ 0245 



+ 0173 



+ 0128 



+ 0222 



+ 0175 



6 13 



+ 0102 



+ 0254 



+ 0158 



+ 0244 



+ 0158 



+ 0130 



+ 0218 



+ 0174 



7 13 



+ 0094 



+ 0188 



+ 0157 



+ 0202 



+ 0106 



+ 0100 



+ 0182 



+ 0141 



8 13 



+ 0068 



+ 0105 



+ 0104 



+ 0120 



+ 0028 



+ 0048 



+ 0109 



+ 0079 



9 13 



+ 0024 



-0006 



+ 0035 



+ 0011 



-0031 



-0003 



+ 0013 



+ 0005 



10 13 



-0036 



-0095 



+ 0003 



-0024 



-0071 



-0053 



-0039 



-0045 



11 13 



-0060 



-0082 



-0038 



-0092 



-0085 



■ -0072 



-0070 



-0072 



146. Diurnal Variation of the Effect of Disturbance on the Total Magnetic Force. The remark made 

 No. 102, for the vertical component, will apply also to the following conclusions obtained from Table 65. 

 \st, The greatest effect of disturbance in increasing the total magnetic force occurs 



In 



About 



Dec. Jan. Feb. 

 Q^ 30™ P.M. 



March, April. 



b^ 30™ P.M. 



May, June. 

 &" 15™ P.M. 



July, Aug. 

 5h 40m P.M. 



Sept. Oct. Nov. 

 b^ 10™ P.M. 



The hours, it will be seen, agree very nearly with those found as the epochs of the maximum total force in the 

 disturbed diurnal variation. The maximum positive effect of disturbance on the total force, occurs latest near 

 the solstices and earliest near the equinoxes. 



2d, The greatest effect of disturbance in diminishing the total magnetic force occurs 



In 



About 



Dec. Jan. Feb. 

 2h 0™ A.M. 



March, April. 

 2h 15™ A.M. 



May, June. 

 Si" 0™ A.M. 



July, Aug. 



2'^ 45™ A.M. 



Sept. Oct. Nov. 

 2^ IQm A.M. 



These hours are nearly the same as those for the after-midnight minimum of the diurnal variation ; the 

 difference is greatest in the summer months when the maximum negative effect occurs latest. 

 3d, The effect of distm-bance on the total magnetic force is zero 



In 



About I 



Dec. Jan. Feb. 



IC" 45™ A.M. 



gh 40m P.M. 



March, April. 

 IQl" 15™ A.M. 



Qh IQ™ p.m. 



May, June. 

 10'' 10™ A.M. 

 lOh 15™ P.M. 



July, Aug. 

 U'' 15™ A.M. 



9h 30™ P.M. 



Sept. Oct. Nov. 

 9^ 45™ A.M. 

 8'' 45™ P.M. 



The one of these epochs is nearly the same as that of the principal minimum in the undisturbed diurnal varia- 

 tion ; the other occurs about twelve hours after. 



