128 



ON THE NUMERICAL RELATIONS OF GRAVITY AND MAGNETISM. 



TABLE V. DAILY MAGNETIC TIDES, THEORETICAL AND OBSERVED. 



Hours from 

 Midnight. 



Theoretical 



Gravitation 



Tide (A). 



Theoretical 

 Differential 

 1 Solar Tide (B). 



(A + B)* 



Theoretical 



Mean Tide (C) . 



Observed 



Mean 

 Tide (D). 



Difference 

 (C-D). 



6 

 H 



a 



o 

 M 

 O 



K 







—.00067 



+.00024 



—.00043 



—.00013 



.00000 





1 



—.00058 



+.00021 



—.00037 



—.00043 



—.00006 



.1:. 00002-|- 



2 



—.00050} 



+ .00012 



— .00038}- 



—.00041$ 



—.00003$ 



±.00003$ 



S 



— .00033$ 



.00000 



— .00033$ 



—.00038} 



—.00005 



± 00002$ 



4 



—.000161 



—.00012 



—.000281 



—.00035$ 



—.000063 



±.00000$ 



5 



—.00009 



—.00021 



—.00030 



—.00030 



.00000 



q=. 00004 



6 



.00000 



—.00024 



—.00024 



—.0002::.'; 



+.00000$ 



~F.00008$ 



7 



+ .00009 



—.00021 



—.00012 



—.00009$ 



+ .00002$ 



=F. 00010$ 



8 



+.00016| 



—.00012 



+.0000l:| 



+.00011$ 



+.000061 



=F.00008$ 



9 



+.00033J- 



.00000 



+.000331 



+.00037 



+.00003$ 



T.00003 



10 



+.00050$ 



+.00012 



+.000623 



+.00061$ 



—.000001 



±.00001$ 



11 



+.00058 



+.00021 



+.00079 



+.00083$ 



+.00004$ 



±■00001$ 



.. 



+.00067 



+.00024 



+ .00091 



+.00095 



+.00004 





Column A contains the hourly differences from mean weight attributable to solar gravi- 

 tation, with changed signs, — diminution of weight being accompanied with increase of 

 magnetism, and vice versd. 



The form of the tide in column B is evidently such as should be determined by solar 

 action. The magnitude of the tide is estimated by comparing the relative amounts of 

 motion down the diagonal and down the arc of a quadrant (.00067x[l.— (|— - J)] = 

 .00048). The mean-tidal difference [(.00067— .00048)+2] is very nearly equivalent to the 

 average theoretical inertia-disturbance of weight. The atmospheric inertia at St. Helena 

 (regarding the fluctuations as uniform between two successive hourly observations), pro- 

 duces retardations of 59', 85', 26' and 31', at 0", 6", 12", and 18", respectively. The mean 

 retardation is 50', or J 2 of a half-day. The daily gravity- variation being .00134, the 

 average variation in T * s of a half-day is .00009 \\, the mean-tidal difference being 00009 i. 



The signs of the differences (C — D) are apparently determined, as in column A, by the 

 variations of weight ; the magnitude, partly by the differences of pressure in the corres- 



* Compare SeccM's Third Law, Phil. Mag. [4], 8, 396. 



The upper signs are for the morning, the lower for the evening hours. 



