or THE MAGNETIC FORCE. 



57 











Monthly Normals. 













Tear. 



January. 



Felj'u'ry. 



March. 



April. 



May. 



June. 



July. 



August, 



Sopt'ber. 



Octoter. 



Nov'ber. 



Dec'ber. 



18-12 . 



658 



707 



658 



659 



656 



655 



662 



677 



682 



706 



716 



710 



1843 . 



702 



710 



691 



707 



686 



678 



677 



691 



708 



710 



742 



746 



1844 . 



731 



728 



760 



756 



756 



758 



796 



773 



801 



778 



770 



749 



Mean . 



697 



715 



703 



707 



699 



697 



712 



714 



730 



731 



743 



735 



Corr'd 



+19 



+16 



+12 



+ y 



+ 5 



+ 2 



— 2 



— 5 



— 9 



—12 



—16 



—19 



Corr'd m. . 



716 



731 



715 



716 



704 



699 



710 



709 



721 



719 



727 



716 



Mean monthly val. 



— 1 



—16 







— 1 



+11 



+16 



+ 5 



+ 6 



— 6 



— 4 



—12 



— 1 



The vertical force appears, therefore, to be greater in May, June, July, and 

 August, and less in the remaining months; the range is about 32 scale divisions 

 ^=0.00105 parts of the force, or 0.0135 in absolute measure. 



