301 



Half-year October to March. 



Principal maximum, 5| hours before the moon's passage of the 

 upper meridian. 



Principal minimum, 3 hours before the moon's passage of the lower 

 meridian. 



Secondary maximum, 5 \ hours after the moon's passage of the 

 upper meridian. 



Secondary minimum, 1 hour after the moon's passage of the upper 

 meridian. 



Half-year April to September. 



Maximum, 4J hours before the moon's passageof the upper meridian. 

 Minimum, at the passage of the lower meridian. 



In the case of the half-year including the June solstice, the secon- 

 dary points disappear ; this also is the case for each of the quarters 

 forming the half-year. It may be due to this and the preponderance 

 of the disturbance in one half of any given year, that the mean for 

 the whole year shows distinctly or indistinctly the secondary points : 

 the question, however, of the secondary points will be considered here- 

 after in another discussion including a longer series of observations. 



The mean value of the lunar disturbance of magnetic) _ QI.OA\ 

 decimation for the six years 1854-59 at Trevandrum . . > 



The maximum value at 5 hours before the upper passage = 0''363 



The minimum value near the inferior passage = 0'-324 



So that the variation of the mean law is only 0''04, or about two 

 seconds and a half. 



When we examine the means for the separate years, we find 



1854 . 



1855 . 



1856 . 



1857 . 



1858 . 



1859 . 



I have not at hand the mean solar disturbances for each year, and 

 cannot therefore compare the two ; it will appear, however, from a 



VOL. XT. y 



