230 Abstracts of the Makerstoun Observations, 1843. 
TABLE VIII.— Continued. 
Civil 
Day. 
Til Ti n O Y*\7 
tj tin Hiii y . 
■ — — 
March. 
April. 
May. 
June. 
July. 
August. 
September. 
October. 
November. 
December. 
0*00 
0*00 
6-00 
O00 
O'OO 
0-00 
0-00 
0-00 
000 
0-00 
O-oo 
19 
1638 
[1817] 
[1509] 
1790 
2567 
2903 
2832 
2617 
2731 
3678 
[3972] 
4566 
20 
1760 
1716 
1440 
laOU 
9 1 1 Q 
Zooo 
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 
1/60 
[iOOD J 
O £iQ i 
ooU / 
A C O ft 
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 formulas : — 
Jan. 1— April 26. / = (ti — 530) 0-0001021 + 0-001000 
April 29— May 6. /= (» - 488) 0-0000986 + 0 001000 
May 8— Nov. 8. /= (» - 485) 0-0000986 + 0-001000 
N 0V . ll_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 succeeding the adjustment was equal to that, ri, 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, producing 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 1844. 
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. 
