OF THE MAGNETIC DECLINATION. 
507 
sage exceeds the one between the superior and the inferior, is rather due to an accidental 
irregularity than to an actual change; but the latter is undoubtedly the case with 
reference to the maximum, comparing it with the summer semiannual curve obtained 
irrespectively of the moon’s declination. 
Ad III. 3. This curve shows but one distinctly expressed maximum and minimum, 
viz. at ll h (or perhaps near the inferior transit) and at 7 h , the range of oscillation 
amounting to 2 3"* 72. 
The intersecting points are in this group of curves more distinctly determined than in 
either of the two preceding ones ; they are at 15 h , 20 h 40 m , 3 1 ' 30 m , and 9 h 50 m . 
Prior to entering on the examination of the lunar-diurnal variation in various years, I 
may be permitted to add a few words on the semiannual inequality for the several 
groups of curves, taking in every one of the annexed diagrams the annual curve for the 
axis of projection. 
Diagram I. in the annexed woodcut illustrates in the usual manner the semiannual 
inequality of the lunar-diurnal variation, no distinction being made respecting the name 
of the moon’s declination. 
Diagram II. shows the semiannual inequality of the lunar-diurnal variation only for 
declinations of the moon south of the equator. 
Diagram III. represents the semiannual inequality of the lunar-diurnal variation for 
declinations of the moon north of the equator. 
Semiannual Inequality of the Lunar-diurnal Variation. 
Inferior Passage. Superior Passage. 
In every one of these cases the summer branch (October to March) bears the character 
of the lunar-diurnal variation, even as far as the turning hours are concerned. We 
