DISCUSSION U F T H E I) I I II N A L V A 111 A T I O X 



Scale 



-SolAR-DIURXAL VARIATION OP THE HORIZONTAL FORCE ; OCTOBER TO MARCH, 1840 TO 1845. 



V = 0.0000365 parts of the horizontal force. 



October. 



November. 



December 



January. 



rVbrnary. 



1234567 



8 9 10 11 N. 13 14 15 16 17 18 19 20 21 22 23 24 h 

 Philadelphia mean time. 



Table VI. contains the coefficients B l B 2 B% Z? 4 of the general equation: 

 A h --= A + B l sin (0 + (7,) + B 2 sin (26+ C 2 ) + Ii 3 Kin (3 + C s ) + B 4 sin (40+ Q 

 expressed in parts of the horizontal force, by multiplying the corresponding quan- 

 tities in the preceding equations with the value of a scale division. The angles 

 (7, C 2 C 3 C 4 will be found in Table VII.; they are the same as given before, 

 increased by 180, so as to make a corresponding change in the direction of the 

 scale readings; increasing numbers will now indicate increasing force. 



