382 



Results of Makeestoun Observations, 1844. 



TABLE XLVII. — Mean Variations of the Vertical Component of Magnetic Force, with reference 

 to the Moon's Hour-Angle for each Lunation, for the Six Winter and Six Summer Lunations, 

 and for the Twelve Lunations, of 1844. 



Diurnal Variation with reference to the Moon's Hour-Angle.' — Considering tlie variations for tlie six winter 

 hiuations, the six summer lunations, and for the year, as given in the last three columns of Table XLVII. 



In the winter gi'oup, the maximum of the vertical component occurs about 2| hours after the moon's transit 

 of the inferior meridian, and the minimum about 3 hours after its transit of tlie superior meridian. 



In the summer group, there are two maxima and two minima ; the principal minimum occurs 4 liours 

 before tlie moon's inferior transit, and the principal maximum occurs 4^ liours after the inferior transit ; a 

 secondary minimum occurs about 4^- hours befoi-e the superior transit, and a secondary maximum at the 

 superior transit. 



In the mean of the 12 lunations in 1844, the maximum occurs 3^ hours after the interior transit, and 

 the minimum occurs 7 hours after the superior transit. There is a secondary maximum immediately bet'ure 

 this epoch, but it is not well marked. The remarks already made for the similar discussion of the horizontal 

 component also apply here. In order to eliminate the ettect of disturbances, those observations were rejected 

 in the summations, which were considerably disturbed, differing from the montlily means at the corresponding 

 hours by more than 50 micrometer divisions (=:0'000o00), ([uantities interpolated from the preceding and 

 succeeding observations having been substituted. The follomng are the resulting variations at intervals of || 

 of an hour: — 



1 2 3 4 5 (i 7 8 9 10 11 12 13 14 1.5 16 17 18 19 20 21 22 23 24 



0-0000 I 37 31 29 22 17 20 06 00 04 12 24 32 47 59 73 77 83 70 58 43 40 39 34 39 36 



The maximum occurs about 2 hours after the moon's passage of tlie inferior meridian, and the minimum 

 7 hours after the superior transit ; there is an ill-defined minimum about 3 hours before the superior transit, 

 and maximum at the superior transit. 



