398 



Results of Makerstoun Obsekvations, 1844. 



TABLE LIX. — Variations of the Total Magnetic Force with reference to the Moon's Hour- Angle, 

 as deduced from Tables XXXI. and XLVII. 



The variations in Tabic LIX. give the following epochs of maxima and minima. In the winter group, 

 containing those lunations for which the moon is full when north of the equator — 



The maximum occurs about 2 hours after the moon's inferior transit. 

 The minimum 2 hours after superior transit. 



There ai'e appearances of a secondary maximum and minimiun, but they are not distinct : the whole range 

 of the moan variations for tlie group is 0-000200, which is only one-fourth less than the range of the solar 

 diurnal variations in the mean for the year. 



In the summer group, there are two nearly equal maxima and two minima — 



A maximum occurs about 4 hours after the moon's transit of the inferior meridian. 



A minimum 5 before superior 



A maximum when the moon transits the superior meridian. 



The minimum about 4 hours before the moon's transit of the inferior meridian. 



The range of tlie variations is only 0000082. 



In the mean for tlie year, there are only one maximinn and one minimum well marked — 



The maximum occurs about 2 hours after the moon's transit of the inferior meridian. 

 The minimum 5 superior 



Minima actually occur 3 hours and 7 hours after the superior transit, but the intervening maximum is 

 very slightly marked. The range of the variations is 0'000120. 



The following moan variations for the year have been obtained from those for the two components, pages 

 365 and 382, for which the large disturbances were rejected : — 



01. 0'" 21" 2.5"' 41' 20"' G^ 1.5"' 8'' 10"' 10' 5<" 12'' O" IS'' 0.5-" lo>' 50"" 17'' 45"' W 40" 21'' 35" 



0-0000 1 28 20 19 00 07 25 56 79 66 45 27 32 



These quantities give the following epochs : — 



The principal maximum occurs about 2 hours after the moon's transit of the inferior meridian. 



A secondary minimum 5 hours befoi-e superior 



A secondary maximum the time of superior 



The principal minimum 6 hours after superior 



The secondai7 maximum is not well marked ; the whole range of the variations is less than 0000100, 

 the total magnetic force being unity. The elimination of the larger disturbances renders the variation for the 

 year neai-ly similar in its epochs to that for the summer group ; it is probable, therefore, that the differences 

 between the vai-iations for the summer and winter gi'oups is chieHy due to disturbances. 



