234 
Abstracts of the Makerstoun Observations, 1843. 
The mean at 18 h in January is rendered comparable with the means at the other hours thus ; the daily 
means from January 9-14, being the means of 8 daily observations, were corrected by +0 - 15 sc. div., obtained 
as for Table VIII., in order to reduce them to the mean of 9 daily observations, then, — 
Sc. Div. 
Mean of Bifilar readings, January 9-31, = 537 - 36 
16-31, = 537-14 
Difference, = 0-22 
The mean for 18 h deduced from the observations January 16-31, was tnctefore corrected by +0-22, in 
order to reduce it to the mean from January 9 to 31, as for the other hours. 
TABLE XI. — Diurnal Variations of the Horizontal Component of Magnetic Force in 1843, the whole 
Horizontal Component being Unity. 
Periods. 
18K 
20 h . 
22\ 
23\ 
0 h . 
2 h . 
4*. 
6\ 
8K 
10*. 
Range. 
Months. 
000 
0-00 
0-00 
0-00 
000 
0-00 
0-00 
0-00 
o-oo 
0-00 
0-00 
January 
0448 
0433 
0000 
0041 
0519 
0705 
0457 
0347 
0378 
0705 
February 
0217 
0543 
0000 
0124 
0461 
0655 
0379 
0472 
0375 
0655 
March 
0697 
0628 
0042 
0000 
0806 
1255 
1273 
1045 
0946 
1273 
April 
1037 
0919 
0000 
0122 
1207 
1969 
2438 
1827 
1279 
2438 
May 
1009 
0617 
0000 
0270 
1516 
1999 
2591 
2563 
1499 
2591 
June 
1229 
0759 
0000 
0337 
1391 
2034 
2384 
2747 
2263 
2747 
July 
1131 
0912 
0000 
0198 
1322 
2653 
2938 
2727 
2048 
2938 
August 
1107 
0686 
0000 
0443 
1745 
2437 
2691 
2492 
2345 
2691 
September 
1353 
0836 
0000 
0477 
1360 
2050 
1747 
1867 
1746 
2050 
October 
1220 
0872 
0000 
0175 
1241 
1629 
1674 
1641 
1529 
1674 
November 
0587 
0495 
0000 
-0071 
0117 
0637 
0745 
0799 
0555 
0430 
0799 
December 
0543 
0550 
0110 
0058 
0071 
0150 
0379 
0196 
0160 
0000 
0550 
Quarters. 
Spring 
0636 
0683 
0000 
0068 
0811 
1279 
1349 
1101 
0853 
1349 
Summer 
1123 
0763 
0000 
0268 
1410 
2229 
2638 
2679 
1937 
2679 
Autumn 
1227 
0798 
0000 
0365 
1449 
2039 
2037 
2000 
1873 
2039 
Winter 
0489 
0456 
0000 
0040 
0399 
0573 
0447 
0317 
0233 
0573 
Half- Years. 
Winter 
0593 
0562 
0000 
0063 
0610 
0869 
0771 
0678 
0584 
0S69 
Summer 
1144 
0788 
0000 
0308 
1423 
2190 
2465 
2370 
1S63 
2465 
The Year 
0868 
0674 
0000 
0185 
1016 
1529 
1617 
1524 
1223 
1617 
Secular Change of the Horizontal Component of Magnetic Force. 
The mean change of the horizontal component from 1842 to 1843 has been determined in the following 
manner. 
By the means for the year 1844, it has been found that the mean of the observations at 22 u and 0 h , is 
greater than the mean at 23 h by 0-000162, and that the mean of the observations at 4 b and 6 U is greater than 
the mean at 5 h by 0-000027, whence from the last line of Table XL, — 
Mean of 22" and 0" =s +0-000092, corrected to mean for 23 u = -0 000070 
Mean of 4 b and 6 h = + 0-001573, corrected to mean for 5 U = + 0 001546 
