Total Magnetic Force. 



253 



Ftom this table, the principal minimum occurs about l^^ 10"" a.m. in the mean for the year, about midnight 

 in winter, and about 2^ a.m. at the equinoxes and in summer. 



The results from Table XXVI. differ little from those deduced from|Table XXV. The secondary maxi- 

 mum occurs earlier in summer than at the other periods, namely, about 6*^ a.m. in summer, and about 8^ a.m. 

 in winter and at the solstices. The following are the periods for the year : — 



The principal maximum occurs at 6*^ p.m., Makerstoun mean time. 



The principal minimum occurs at l^^ 10™ a.m., 



A secondary maximum occurs at 8^ a.m., 



A secondary minimum occurs at 10'* 40™ a.m., 



Ranges of the Monthly Means of the Diurnal Variations of the Total Magnetic Force. 



It is CTident, from the previous results, that the quantities in the last column of Table XXV. are not at 

 all the diurnal ranges, as the minimum occurs near midnight. From Table XXVI., however, it appears that 

 the range of the mean diurnal curve for the months about the winter solstice is 0'000240, about the equinoxes 

 is 0-000744, and about the summer solstice is 0-000506 ; or, that the ranges are nearly in the following ratio : — 



Winter Solstice : Summer Solstice : Equinoxes :z 1 : 2 : 3. 



TABLE XXVII. — Variations of the Total Force of the Earth's Magnetism with reference to the 

 Moon's Age, Declination, and Distance from the Earth, as deduced from Tables IX. and XVI. 





Variations 





Variations 



After 



Variations 



After 



Variations 



Before 



Variations 



Before 



Variations 



Moon's 



of 



Moon's 



of 



Moon 



of 



Moon 



of 



and 



of 



and 



of 



Age. 



Magnetic 

 Force. 



Age. 



Magnetic 

 Force. 



farthest 

 North. 



Magnetic 

 Force. 



farthest 

 North. 



Magnetic 

 Force. 



After 

 Perigee. 



Magnetic 

 Force. 



After 

 Apogee. 



Magnetic 

 Force. 



Days. 



15 



0-000 



037 



Days. 







0-000 



040 



Days. 







0-000 



130 



Days. 



14 



0-000 



073 



Days. 



7 



0000 



107 



Days. 



7 



0-000 



052 



16 



058 



1 



025 



1 



087 



15 



057 



6 



086 



6 



022 



17 



073 



2 



066 



2 



146 



16 



033 



5 



164 



5 



051 



18 



064 



3 



083 



3 



092 



17 



005 



4 



058 



4 



045 



19 



048 



4 



049 



4 



064 



18 



033 



3 



040 



3 



027 



20 



082 



5 



042 



5 



035 



19 



017 



2 



062 



2 



025 



21 



087 



6 



145 



6 



041 



20 



027 



1 



083 



1 



040 



22 



071 



7 



040 



7 



056 



21 



009 



P 



053 



A 



031 



2.3 



076 



8 



067 



8 



066 



22 



015 



1 



056 



1 



000 



24 



073 



9 



048 



9 



042 



23 



028 



2 



087 



2 



035 



25 



095 



10 



036 



10 



026 



24 



000 



3 



084 



3 



051 



26 



084 



11 



053 



11 



043 



25 



060 



4 



076 



4 



094 



27 



049 



12 



001 



12 



053 



26 



037 



5 



080 



5 



095 



28 



154 



13 



000 



13 



087 



27 



085 



6 



043 



6 



120 



29 



058 



14 



016 











7 



047 



7 



101 



Variations op the Total Magnetic Force with reference to the Moon's Age. 



Means of Groups. 



14 days to 16 days, Full Moon. 0000037 



17 20 - 0-000067 



21 24 ••• 0-000077 



25 28 ... 0000095 



29 days to 1 dav, New Moon, 



2 5 ••• 



6 9 ••• 



10 13 ... 



0000041 

 0000060 

 0-000075 

 0-000022 



From these means the total force is a minimum when the sun and moon are in opposition and in conjunction, 

 and a maximum about the quadratures. The principal minimum occurs at the time of full moon. 



MAG. AND MET. OBS. 1843. 3 S 



