DISCUSSION OF THE VERTICAL FORCE. 



13 



tbe process was repeated, if necessary, until all deviations above 30 had been sepa- 

 rated; the final hourly means for each month, thus found and known as the 

 " normals," are given in the following tables. 



Table IV.— Bi 



-HouELY Normals op the Vertical Component of the Magnetic Force | 













IN 1841. 







One divisi 



311 of tlie scale = 



= 0.000033 parts of the vertical force. Increasing numbers denote decrease of force, j 









The observations are made 17™ after the. full hours. 







1841. 



0" 



2 



4 



6 



8 



10 



Noon. 



14 



16 



18 



20 



221' 



February 



664 



6d4 



662 



656 



654 



650 



644 



648 



647 



. 673 



668 



665 



Marcli 



670 



661 



661 



655 



651 



645 



643 



646 



656 



665 



666 



673 



April 



671 



662 



658 



653 



645 



646 



646 



649 



656 . 



666 



670 



676 



May 



669 



665 



660 



654 



647 



649 



644 



646 



650 



660 



674 



679 



June 



646 



631 



622 



617 



624 



616 



603 



624 



635 



650 



653 



. 657 



July 



703 



697 



687 



671 



667 



664 



665 



676 



680 



698 



708 



706 



August 



686 



680 



676 



664 



662 



652 



653 



662 



666 



676 



689 



691 



September 



6 '33 



655 



646 



647 



637 



631 



627 



628 



634 



645 



653 



660 



October 



579 



578 



573 



568 



558 



556 



561 



562 



571 



677 



581 



583 



November 



532 



537 



538 



533 



526 



523 



520 



521 



526 



529 



531 



538 



December 



597 



591 



590 



606 



592 



598 



605 



597 



607 



610 



605 



604 



The normals for February, March, April, and May, have been diminished by 198, 

 278, 333, and 361 scale divisions respectively; the uncorrected monthly means are 

 856, 936, 991, and 1019, Avhich can be exactly represented by the expression r= 

 966 + 54.4 At — 12.8 Af, where r= monthly reading and^, expressed in units of a 

 month, counts from April 1 as the epoch. It shows that the monthly increase is 

 uniformly retarded. The mean reading from the four succeeding months is 658, 

 the corrections to February, March, April, and May, as applied, will produce the 

 same mean. 



The rapid change in the monthly means for some adjacent months makes a small 

 correction necessary to the monthly means, viz : of plus one scale division to the 

 February, March, and December means of the hours 0, 2, and 4, and to the Septem- 

 ber and October means' at the hours 18, 20, and 22; of minus one scale division to 

 the February, March, and December means at the hours 18, 20, and 22, and to the 

 September and October means at the hours 0, 2, and 4. This small correction is 

 included in the above normals. 



Table IV.- 



-Continued. Bi-hourly Normals o 



F THE Vertical Component 



IN 1842. 









The observations 



are made 171"" after the full hours. 





20 



22" 



1842. 



O'' 



2 



4 



6 



8 10 



Noon. 



14 



16 



18 



January 



(658; 



642 



656 



649 



656 1 653 



664 



650 



663 



675 



670 



663 



February 



706 



701 



713 



721 



699 



698 



709 



692 



698 



712 



723 



710 



March 



655 



■ 43 



654 



663 



657 



661 



651 



650 



657 



668 



673 



665 



April 



668 



658 



655 



655 



656 



654 



657 



651 



650 



660 



672 



672 



May 



673 



670 



661 



644 



646 



647 



651 



644 



645 



656 



668 



670 



June 



674 



669 



6li4 



658 



647 



642 



635 



639 



635 



653 



671 



668 



July 



683 



672 



664 



659 



657 



650 



643 



643 



647 



663 



677 



682 



August 



689 



689 



683 



682 



679 



672 



652 



659 



669 



679 



688 



688 



September 



692 



686 



t;89 



690 



681 671 



671 



673 



672 



679 



687 



693 



October 



706 



698 



702 



714 



695 1 708 



707 



706 



706 



708 



710 



709 



November 



717 



713 



723 



725 



712 715 



711 



713 



716 



712 



718 



718 



December 



713 



707 



709 



706 



715 711 



709 



707 



706 



711 



713 



713 



