145 



a combination of the oscillations for a positive and negative secular 

 motlon. 



The mean range of the annual period at Makerstoun is 0'*96. 



The variation with reference to the moon^a age, consists of 



A principal maximum 2 days after full moon. 

 A principal minimum 2 days after new moon. 



with two secondary maxima and two secondary minima, which are 

 exhibited with considerable regularity in each of the results for 4 

 years. The range of the mean = 0''83. 



The variations with reference to the moons declination and dis- 

 tance from the earth are less distinct for evident i-easons. The 

 former seems to consist of 



The maximum about the time of the moon's greatest N. declination. 



Minima when the moon is on the equator. 



A secondary maximum of the moon's greatest S' declination. 



Diurnal periods. 1. The Sun^s hour angles. In the mean of 

 two years observations (1844-5), the north end of the needle moves 

 nearly 8' towards the west from G*" 1 a.m. till 45°^ past noon, and 

 as much to the east from the latter epoch till IP p.m. ; from ll** 

 P.M. till 2*^ 35 A.M., the north end of the needle moves CK*? towards 

 the west, returning to the east again about as much by 6** a.m. The 

 epoch of the greatest westerly declination seems to be connected with 

 its annual period, or with the value of the mean westerly declination, 

 and the epoch of the principal mininum, with the sign of the secular 

 change. The author considers that the diurnal oscillation is double 

 at all seasons of the year. 



2. The Moon's hour angles. The following are the result. 



Moon in opposition north of the equator; mean of 13 lunations ; 

 oscillation single ; range = 0'"8. 



Maximum l** before inferior transit. Minimum 4** or 5'' before 

 superior transit. 



Moon in opposition south of the equator; mean of 12 lunations; 

 oscillation double ; range = 0'- 6. 



Maximum 2a'', and minimum 6^ after superior transit. Second- 

 ary maximum at inferior transit. Minimum b^ after it. 



Moon in opposition northward, south of equator ; mean of 25 lu- 

 nations ; oscillation double ; iange = 0'*6. 



Secondary maximum 4^'', and minimum 8^ after superior transit. 

 Maximum at superior transit, minimum 6'' after it. 



Single lunations verify those epochs very nearly. 



