OP THE MAGNETIC FORCE. 



49 



(D). SOLAR-DlURNAL VARIATION OP THE VERTICAL FORCE, OCTOBER TO MARCH, 1841 TO 1845. 



(Expressed in scale divisions.) 

 1" = 0.000033 parts of the force. 



0" 2 



10 14 16 18 20 22 24" 



I 

 Philadelphia mean time. 



