556 
COLONEL SABINE ON THE INFLUENCE OF THE MOON ON THE 
Table V. 
The differences between the deflections at opposite points of the hour-circle at 
this station have so much the character of mere accidental irregularities that we 
may venture for greater simplicity to combine them, as is done in the two last colu 
of Table V., and to represent the deflections thus combined by a formula of 
terms, in which a, the hour-angle (reckoned from eighteen hours), is multiplied by 
30° instead of 15°. The formula is as follows : — 
A,= -f-02625 + -1259sin (a-l-3l7° 5l')+-01047 sin (2a-b25° 57') 
— •0083 sin (3fl-b5° 43 ') + -01 18 sin (4a-l-287° 48') 
+ •00235 sin (5a+29i° 26 ') + -0029 cos 6 a. 
The lunar diurnal variation at St. Helena is, as at Toronto, a double progression, 
having two westerly extremes at nearly opposite points of the hour-circle, and two 
easterly extremes also at nearly opposite points. The amounts of extreme deflection, 
both easterly and westerly, are considerably less than at Toronto, but exhibit the same 
peculiarity of the extreme elongations in the one direction being about one-third 
greater than the extreme elongations in the other direction ; at Toronto, the easterly 
elongations are the greater, at St. Helena the westerly. But a still more remarkable 
distinction in the lunar variation at the two stations respects the lunar hours at 
which the elongations respectively occur. At Toronto, as we have seen, the two 
easterly extremes coincide nearly with the epochs of the moon’s superior and inferior 
culminations, and the westerly extremes nearly with the quadrantal hours of 6 an 
18. At St. Helena, on the other hand, neither the times of the easterly nor o 
the westerly elongation coincide either with the culminations or with the hours of 
6 and 18 ; and are so far and so systematically distant from those hours as to leave 
no doubt of the reality of their differences from them. The above formula gives 
for the times of extreme easterly deflection at St. Helena 3^’ 24“ and 15*' 24“ ; an 
for the times of extreme westerly deflection lO’^ 6 “ and 22 ^ 6 “; and the fom- hours 
at which the lunar variation disappears, or becomes 0, are 2^’ 0“ 6 '' 53“ 14' 0“ an 
