436 
TaB_E I.—Diurnal Variation of the Declination, related to the Moon’s 
Hour-Angle. Yearly Means. 
Hours. 1841. 1842. 1843. Mean. 
0 — 036 —0’20 | —0’-23 | —0’26 
2 — 0°26 — 0:15 —0'14 -—0°18 
4 — 0:05 + 0:04 +0°14 +0:04 
6 +057 | +0°43 +0:°27 | +042 
8 +0°36 | +0°32 | +0°02 | 40-23 
10 + 0°43 — 0°25 -— 0°43 — 0:08 
12 — 0°45 — 0°50 — 0:48 — 0°48 
14 — 0:72 — 0°38 — 0°43 — 0°51 
16 
18 
20 
22 
-0:01 — 0°27 + 0:06 —0°07 
+ 0°06 + 0:32 + 0°56 +031 
+ 0°52 + 0°42 + 0°37 + 0°44 
— 0:09 +019 + 0:23 +011 
It will be seen from the foregoing Table that the posi- 
tion of the freely-suspended horizontal magnet varies with 
the moon’s hour-angle, the north pole deviating twice to the 
east, and twice to the west, in the course of the lunar day. 
The extreme westerly deviations occur about 0 and 13 (lunar) 
‘hours, or soon after the moon’s meridian passage, above and 
below; and the extreme easterly about 64 and 20 hours, or 
soon after the moon’s rising and setting. The mean range, 
measured from the mean of the two greatest westerly elon- 
gations to the intervening easterly, is 0°82, when the moon 
is to the east of the meridian, and 0°80 when the moon is west. 
The mean range due to the sun’s action being 96, the lunar 
range is to the solar as 1 to 12,—a result which accords very 
nearly with that before derived from a different analysis of 
the phenomenon. 
A marked difference having been elsewhere obtained be- 
tween the laws of this phenomenon in summer and in winter, 
it has been thought necessary to separate the results of the 
summer and winter lunations: they are given in the two fol- 
lowing Tables, of which Table II. contains the mean results 
for summer, and Table III. those for winter. 
