378 A. D. Bache 07i the Horizontal Component of Magnetic Force. 





n 11 II ■ ■■ lllntaml! 





Morning a,a.i. Morning ™ini- 









^.. II .... 1 



max. 



Afternoon ">'" ^_^_'^„ 







d. -KT^ 















January. 





-9-2 ir 5o 



+ I5-7 





- 5-3 









Februry. 



7 15 



-96 U40 







- ^^^ 









March. 











- 23 







43^ 



H' 



5ll 



:| ii 



M 



3 55 



:ll 





+3 





July. 









2 45 



~[ll 





i 



435 



Se^'ptember 



5 35-4 9 ^o=o 



+25-9 



3o5 



-'67 







4 45 



October. 



5oo -1.-6 11 i5 



+ .3-7 



5 10 













6 00-9-8 u 25 







zVo 









DeSber 



5-&^^ -7^3V 

 6.5-9-4 II 45 



i 



3^5 



^oT 



"f" 



+4 

 +3 



-jir 



ir 







+.5^ 



3 35 





2^1 



11-5 





Tabl 



IX.- Amplitude of the diurnal variation of the horizontal force. 





~zz:. 





F0,..M. 





ro,..« 



ror...^-. 

















fe 



h 



Jai 



o-ooog; 



°°°°oll 



O.0O3S 



ooo3a 



March, 

 April, 



256 



29-1 



093 



068 

 J06 



^I 



1 



May, 

 June, 





25-3 



36.1 

 390 



i 



z 



i34 



36 



59 



s;- 



B 



32-6 



i 



o5? 



40 



2? 



Nov., 







o?6 



o5? 



32 





Wintl'r? 



~w 



I?; 



0-00.03 



077 

 £^9 



^1 



i 



Year, 



25-2 



-a¥-di^n7 



000092 





°o^ 











fisr^^' 



-^h^ 



In 



i^ 



!!!_— ^ 



The next table (X) contains the epochs when the mean toriz.^^' 

 tal force is reached in each day, as computed by the preceamo 



■ --sect the axis of absciss® four 



only the A. M. and first P.M. 



formulae. The diurnal 



times, of which the table 



intersection, those later in 1 



in summer, winter and the whole year at 7 P. M., 5| ?■ 



^ p. M. respectively, and at 11^ P. M., 12 P. M., Hf ^- ^^ 



speetively. 



The above times are generally 



cording to the forraute). 

 horizontal force is less variable i 

 afternoon hour. 

 Diagram (G) exhibits the cha 



within 2 minutes (ac- 



' of average c 



3 of a year 



than t 



I the horizontal force i 



solute measure from the monthly normal value for eacti hoar 



