Vertical Component of Magnetic Force. 



xlv 



80. The result for the winter lunations of 1844 agrees with this, in shewing a maximum immediately after 

 the inferior transit ; but differs from it in having the minimum about the hour of the second maximum for the 

 other periods ; this difference, it is conceived, is chiefly the effect of disturbances, as has been found when the 

 larger disturbances were eliminated. (See the volume for 1844, p. 365.) 



Vertical Component of Magnetic Force. 



81. Observations for the absolute value of the vertical component were made in 1846 in the manner 

 described in the Introduction to the Observations for 1844, p. liii. (foot-note), but they have not been reduced; 

 indeed, it is doubtful whether the dimensions of the magnets employed, and the errors of the instrument were 

 likely to admit a sufficiently accurate result. We may deduce the absolute value of the vertical component 

 from the observations for the horizontal component and magnetic dip ; assuming the latter =71° 15' for the 

 year 1845, we find the mean value of the former from the observations with the large deflecting bar (last 

 column of Table 21) for the year 1845 =3'3837 ; — whence the absolute value of the vertical component of 

 magnetic force for 1845 =9"9680. The following results are deduced wholly from the observations of the 

 balance magnetometer : the variations are given in parts of the whole vertical component assumed equal to unity. 



Table 38. — Monthly Means of the Variations of the Vertical Component of Magnetic Force at 



Makerstoun. 



Month. 



1842. 



1843. 



1844. 



1845. 



1846. 



1847. 



1848. 



1849. 



January 



•012155 



•009905 



•007838 



•005904 



•003917 



•002523 



[•001880] 



•001157 



February 



•011988 



•009708 



■007458 



•005616 



•003737 



•002636 



•001800 



•001004 



March 



•011495 



•009325 



•007341 



•005475 



•003663 



•002659 



■001684 



•000747 



April 



•011446 



•008992 



•007384 



•005361 



•003526 



•002668 



•001379 



•000537 



May 



•011323 



■008804 



■007062 



•005192 



•003603 



•002599 



•001085 



•000472 



Juue 



•011167 



•008878 



•006847 



•005034 



•003936 



■002488 



•000936 



•000467 



July 



•010883 



■008732 



•006552 



•004740 



■003839 



•002415 



•001561 



•000314 



August 



•010797 



•008562 



•006341 



■004643 



•003678 



•002184 



•001197 



•000079 



September 



•010672 



•008158 



•006267 



■004534 



•003584 



■002141 



•000705 



■000129 



October 



•010471 



•008138 



•006129 



■004310 



•003206 



•002299 



•001354 



■000127 



November 



•010355 



•008109 



•006155 



•004307 



■002899 



•002344 



•001361 



■000109 



December 



•010129 



•007992 



•006003 



•004315 



•002643 



•002168 



•001346 



■000017 



82. Table 38 contains the monthly means of the balance magnetometer readings, as deduced from the regular 

 daily observations ; these in 1848 and 1849 were only two daily. From 1842 to 1847 the balance needle 

 occupied a position at right angles to the magnetic meridian ; in 1848 and 1849 its position was in the mag- 

 netic meridian. The monthly means diminish with a few exceptions from month to month throughout the 

 whole period. The yearly means of the variations and secular changes are given in Table 39. 



Table 39. — Yearly Means of the Variations of the Vertical Component of Magnetic Force, 



with the Secular Change. 





Mean of 





Secular Change. 





Year. 



Variations 

 of Vertical 

 Component. 









Year to Year. 



Mean of Each 

 Four Years. 



During Each 

 Year. 



1842 



0^011073 







0-002327 



1843 



•008774 



0-002299 





2108 



1844 



■006781 



1993 





1966 



1845 



•004953 



1828 





1733 



1846 



•003519 



1434 



0-001888 



1151 



1847 



•002427 



1092 



1587 



1077 



1848 



•001357 



1070 



1356 



0867 



1849 



■000430 



0927 



1131 



1125 



