HorIzoNTAL FORCE. XXV 
From this it will be seen that some of the horizontal lines in Table 4 represent 
the average result of a greater number of years than others. This will undoubtedly 
diminish to some extent the value of the Table, and prevent the annual variations 
for the different hours from being so comparable with one another as they would 
otherwise have been. It is believed, however, that the Table is not without 
interest. 
The following Table represents the annual range for the different hours as de- 
duced from Table 4 :— 
TABLE 6.—Declination—Annual Range for the Different Hours. 
Hour ) zs 
G.M.T. } 0 ih 3 4 5 6 7 8 9 roy 11 
Range, | 4-13| 4:55|4-49 |4:52 |3-94 |9-76 | 2-65 [9-74 |2-68 | 2-54 13-15 | 2-11 




G.M.T. 
Range, | 1-72 |1-89 | 1-83 |3-52 |2-86 | 4-17 |3-91 | 6-50 | 4:57 |5-39 | 3-46 | 2-02 
Hour } ee ismimne ts love a7: | leuk do || 90 |) 2t,.),29. k 93 






On examining Table 6 it is perceived that the ranges of variation for the hours 
of the day are greater than those for the hours of the night, the ranges for the 
hours about midnight being especially small. A similar fact has been noticed by 
General Sabine, for Toronto, Hobarton, the Cape of Good Hope, and St Helena. 
(See Transactions Royal Society of London, Part II. for 1851.) 
Another fact, noticed also by General Sabine for these four stations, has its 
analogue at Makerstoun. 
It will be seen that the months June and July go together, being affected with 
a minus sign—that. is to say, having a less than mean westerly declination, or 
being east of the mean position from about 14° to about 23° G. M. T., or from 
1 a.m. to 10 a.m., Makerstoun mean time; while they are affected with a positive 
sign, or are west of the mean position, during the remaining hours. 
Precisely the reverse happens with November and December, which are affected 
with a positive sign, or are to the west of the mean position from about 1 A.M. to 
10 a.m., Makerstoun mean time; while during the remainder of the day they are 
to the east of the mean, being affected with a negative sign. 
HorIzontTaL ForcE. 
The following Table contains the corrections that have been applied to the means 
of the observed readings of the horizontal force magnetometer in order to obtain 
the mean of the day. These corrections have been deduced from hourly observa- 
tions made during 1844 and 1845. 
