230 ABSTRACTS OF THE MAKERSTOUN OBSERVATIONS, 1843. 
TABLE VIII.—Continued. 
January. | February.| March. April. 0 : . |September.| October. | November, 
0-00 0:00 0-00 0-00 + E 0-00 0-00 0-00 
1638 [1817] | [1509] 1790 2731 3678 [3972] 
1760 1716 1440 1850 3119 2885 4236 
1926 1739 1564 1838 2818 3505 4218 
{1703] 1764 2099 : 3141 [3370] 4144 
1321 1906 1760 55 5 3287 3482 3807 
1940 1467 1278 [2961] 3218 4531 
1637 1577 1732 2993 3451 4459 
1524 [1744] | [1655] 2619 2866 [4213] 
2033 1856 1576 2908 3093 4478 
1434 1855 1825 2672 3458 3992 
[1635] 1760 3093 [3232] 4013 
1609 1160 2 3308 2875 4076 
1566 1708 } 3526 
1744 1571 : 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 formule :— 
Jan. 1—April 26. f = (n — 530) .0-0001021 + 0-001000 
April 29—May 6. / = (n — 488) 00000986 + 0-001000 
May 8—Nov. 8. f= (n — 485) 0-0000986 + 0:001000 
Nov. 11—Dec. 31. f= (n — 485) 00001064 + 0-001000—0-000008 
where f 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, n’‘, for the three days preceding 
it. 530 having been taken as a convenient zero for the means before the adjustments, < the zero for the means 
after the adjustment was obtained from the formula 
- 
x 
" 
(n—530) 0:0001021 = (n/ —z2) 0:0000986 Ld 
whence z = 488. 
On May 6 the torsion cirele 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 489. a 
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. 
