234 



Abstracts of the Makerstoun Observations, 1843. 



The mean at 18'* 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, — 



Mean of Bifilar readings, January 9-31, 

 16-31, 



Difference, 



Sc. Div. 

 = 537-36 

 = 537-14 



= 0-22 



The mean for ISi^ deduced from the observations January 16-31, was tnciefore 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. 



18b. 



20*'. 



22''. 



23''. 



0". 



2^. 



41'. 



6^. 



8". 



10''. 



Range. 



Months. 



0-00 



0-00 



O-OI) 



0-00 



00 



0-00 



0-00 



000 



0-00 



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 



Olio 



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-Ycars. 

























Winter 



0593 



0562 



0000 





0063 



0610 



0869 



0771 



0678 



0584 



0869 



Summer 



1144 



0788 



0000 





0308 



1423 



2190 



2465 



2370 



1863 



2465 



The Year 



0868 



0674 



0000 





0185 



1016 



1529 



1617 



1524 



1223 



1617 



Secular Change op 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'» and 0\ is 

 greater than the mean at 23'* by 0-000162, and that the mean of the observations at 4^ and 6^ is greater than 

 the mean at 5*^ by 0-000027, whence from the last line of Table XI., — 



Mean of 22^ and Qi = +0-000092, corrected to mean for 23'* = -0000070 

 Mean of 4:^ and e'' = + 0-001573, corrected to mean for 5^^ = + 0-001546 



