230 



Abstracts of the Makerstoun Observations, 1843. 



TABLE Ylll.— Continued. 



Civil 

 Day. 



January. 



February. 



March. 



April. 



May. 



June. 



July. 



August. 



September. 



October. 



November. 



December, 





0-00 



0-00 



0-00 



0-00 



COO 



0-00 



0-00 



0-00 



0-00 



000 



000 



0-00 



19 



1638 



[1817] 



[1509] 



1790 



2567 



2903 



2832 



2617 



2731 



3678 



[3972] 



4566 



20 



1760 



1716 



1440 



1850 



2453 



3189 



2588 



[2890] 



3119 



2885 



4236 



4355 



21 



1926 



1739 



1564 



1838 



[2653] 



2797 



3033 



3008 



2818 



3505 



4218 



4473 



22 



[1703] 



1764 



2099 



1748 



3003 



2929 



2805 



3086 



3141 



[3370] 



4144 



4564 



23 



1321 



1906 



1760 



[1942] 



2734 



2552 



[2836] 



2856 



3287 



3482 



3807 



4589 



24 



1940 



1467 



1278 



2060 



2643 



2857 



3829 



2874 



[2961] 



3218 



4531 



[4500] 



25 



1637 



1577 



1732 



2057 



2718 



[2751] 



2911 



2712 



2993 



3451 



4459 



4672 



26 



1524 



[1744] 



[1655] 



2099 



2649 



2823 



1852 



2400 



2619 



2866 



[4213] 



4472 



27 



2033 



1856 



1576 





2692 



2648 



2343 



[2854] 



2908 



3093 



4478 



4230 



28 



1434 



1855 



1825 





[2830] 



2693 



2302 



2935 



2672 



3458 



3992 



4092 



29 



[1635] 





1760 



2115 



3380 



3152 



2731 



3100 



3093 



[3232] 



4013 



4151 



30 



1609 





1160 



[2158] 



2782 



3120 



[2547] 



3106 



3308 



2875 



4076 



4122 



31 



1566 





1708 





2758 





2604 



3146 





3526 





[4292] 



Mean 



1744 



1758 



1571 



1662 



2428 



2756 



2653 



2787 



2976 



3160 



3790 



4207 



Table VIII. was formed in the following manner : — the means of the bifilar magnetometer scale readings, 

 corrected for temperature, for each civil day, were first obtained, and these means were reduced to parts of the 

 horizontal component by the following formulfe : — 



Jan. 1— April 26. / = (n - 530) 0-0001021 + 0-001000 



April 29— May 6. / = (n - 488) 0-0000986 + 0-001000 



May 8— Nov. 8. / = (n - 485) 0-0000986 + 0-001000 



Nov. 11— Dec. 31. /= (n - 485) 0-0001064 + 0-001000-0-000008 



where / is the quantity in the previous Table, n the mean scale reading corrected for temperature. 



The Bifilar magnetometer was twice adjusted in 1843 (see Introduction, No. 38). As the means for the 

 three days immediately preceding the adjustment on April 27-28 were nearly equal to each other, and the means 

 for the three days succeeding the adjustment were also nearly equal to each other, it was assumed that the 

 mean force, n, for the three days svicceeding the adjustment was equal to that, n', for the three days preceding 

 it. 530 having been taken as a convenient zero for the means before the adjustments, z the zero for the means 

 after the adjustment was obtained from the formula 



(n-530) 0-0001021 = (n'-z) 0-0000986 



whence z = 488. 



On May 6 the torsion circle was turned, and was not returned to its previous position, produciag a dif- 

 ference of about three scale divisions, the zero after May 6 is therefore 485. 



On the adjustment, Nov. 9—10, the same process was adopted as for that of April 27—28, which gave the 

 zero nearly as before, 484-93 ; 0-001000 has been added to each mean in order to render them all positive. 



The means of the four daily observations in the first week of January were corrected by — 0-000025, and 

 the means of the eight daily observations in the second week by +0-000016, corrections to the mean of nine 

 observations obtained by comparisons of the observations in 1 844. 



The factors used for the above and following Tables in converting the scale divisions into parts of the whole 

 horizontal component, are those given in the Postscript to the Introduction. 



Annual Period of the Horizontal Component of Magnetic Force. 



Differences of the monthly means deduced from the observations in 1844, at the nine hours of 18, 20, 

 . . . 10, from those deduced from the 24 hourly observations made on each day, excepting Sundays, in 

 that year. 



