XXXVlll 



General Results of the Makerstoun Observations. 



diately before and after those stated, a secondary minimum occurring at conjunction, and a secondary maximum 

 at opposition ; but these secondary points are probably accidental. 



2d, The departure of the horizontal component from its monthly mean position for the corresponding hour 

 is least when the moon is farthest south and also when farthest north ; maxima occurring at the intermediate 

 periods (see No. 16). 



Diurnal Variations for the Horizontal Component of Magnetic Force. 



Diurnal Variation of the Horizontal Component. — The discussions for 1843 and 1844 will be found in 

 the volumes for these years, the Tables for 1846 and 1846 are given in this volume, pages 13 and 34. Table 

 31 has been formed from all the ordinary daily observations made in the 4 years, in the manner already de- 

 scribed for the declination (Nos. 26, 27.) 



Table 31. — Diurnal Variations of the Horizontal Component of Magnetic Force for each Month, as 

 deduced from the Regular Daily Observations made during the Four Years 1843 to 1846. 



Mak. 

 Mean 

 Time. 



Jan. 



Feb. 



March. 



April. 



May. 



June. 



July. 



Aug. 



Sept. 



Oct. 



Nov. 



Dec. 



li. m. 



0-00 



0-00 



0-00 



frOf) 



0-00 



0-00 



0-00 



0-00 



0-00 



0-00 



000 



0-00 



12 12 



0456 



0358 



1576 



1746 



1816 



2191 



2346 



2476 



1751 



1672 



0843 



0098 



13 12 



0404 



0202 



0995 



1758 



1743 



1991 



2158 



2182 



1875 



1694 



0884 



0221 



14 12 



0000 



0077 



0893 



1158 



1630 



1856 



2012 



2023 



1592 



1648 



0855 



0227 



15 12 



0630 



0129 



1285 



1572 



1557 



1770 



1918 



2031 



1770 



1918 



1039 



0327 



16 12 



0855 



0252 



1271 



1651 



1476 



1655 



1745 



2029 



1816 



1945 



1162 



0607 



17 12 



1062 



0521 



1329 



1890 



1521 



1480 



1574 



1745 



1978 



1842 



1227 



0791 



18 12 



1054 



0614 



1575 



1805 



1421 



1151 



1435 



1584 



1708 



1654 



1330 



0897 



19 12 



1022 



0641 



1275 



1521 



1008 



0831 



1080 



1027 



1047 



1419 



1125 



0764 



20 12 



0769 



0519 



0709 



0757 



0420 



0329 



0560 



0316 



0550 



0752 



0740 



0573 



21 12 



0616 



0105 



0308 



0145 



0119 



0004 



0094 



0000 



0023 



0180 



0183 



0278 



22 12 



0348 



0000 



0000 



0000 



0000 



0000 



0000 



0140 



0000 



0000 



0000 



0001 



23 12 



0444 



0042 



0208 



0132 



0414 



0518 



0502 



0718 



0531 



0284 



0104 



0000 



12 



0556 



0268 



0632 



0782 



1102 



1284 



1249 



1417 



1268 



0753 



0566 



0097 



1 12 



0932 



0535 



1324 



1557 



1978 



1949 



1915 



2380 



2082 



1484 



0835 



0332 



2 12 



1027 



0784 



1756 



2201 



2530 



2549 



2764 



2781 



2524 



1744 



1028 



0521 



3 12 



1007 



0840 



2071 



2691 



2947 



2891 



3444 



3349 



2860 



2122 



1131 



0604 



4 12 



1057 



0726 



2185 



3003 



3722 



3185 



3753 



3558 



3100 



2078 



1027 



0668 



5 12 



0995 



0658 



2132 



3456 



3969 



3487 



4049 



3997 



2982 



2109 



1431 



0648 



6 12 



0868 



0658 



1958 



3482 



3875 



3685 



4148 



3888 



2827 



2169 



1428 



0888 



7 12 



0819 



0729 



2049 



3026 



3825 



3667 



3847 



3740 



2780 



2059 



1139 



0670 



8 12 



0933 



0714 



1966 



2706 



3177 



3297 



3459 



3402 



2352 



2034 



nil 



0366 



9 12 



0830 



0586 



1769 



2386 



2574 



2933 



2957 



3010 



2314 



1961 



0866 



0249 



10 12 



0623 



0212 



1575 



2484 



2308 



2711 



2654 



2939 



2123 



1875 



0878 



0200 



11 12 



0598 



0264 



1808 



2197 



2004 



2344 



2543 



2625 



2123 



1715 



0776 



0241 



69. The following are the approximate epochs of ma.x;ima and minima in apparent time, as deduced from the 

 numbers in Table 31 ; the principal maximum is distinguished by -\-, the principal minimum by — , 





Jan. 



Feb. 



March. 



April. 



May. 



June. 



July. 



Aug. 



Sept. 



Oct. 



Nov. 



Dec. 





h. m. 



h. m. 



h. m. 



h. m. 



h. m. 



h. m. 



h. m. 



h. m. 



h. m. 



h. m. 



h. m. 



h. m. 



Min. 



22 10 



-22 15 



-22 15 



-22 15 



22 



21 50 



21 40 



21 25 



-21 50 



-22 10 



-22 40 



-22 40 



Max. 



+ 40 



+ 2 45 



+ 4 15 



+ 5 45 



5 15 



6 45 



5 50 



5 10 



+ 4 20 



+ 5 



+ 60 



+ 6 15 



Min. 



-14 



-14 



14 



14 











14 



13 



11 



-12 



Max. 



+ 18 



18 45 



18 



17 30 











17 15 



16 



+18 30 



+ 18 



The diurnal variation of the horizontal component, at Makerstoun, consists of one maximum and one i 



minimum in the four months May till August, and of two maxima and two minima in the eight months [ 



September till April ; in each of the four months November till February, the two maxima have nearly equal , 

 values, and in each of the last three of these, the two minima are also nearly equal ; from March till April, 



