558 COLONEL SABINE ON THE INFLUENCE OF THE MOON ON THE 
the following formula, in which a, the hour-angle reckoned as before from eighteen 
hours, is multiplied by 15 . 
A^= +'0825 — *0487 sin (« + 39° 15') — '2056 sin (2a+38° 00') 
+•0173 sin (3a+339° 41') — '0161 sin (4a+68° 56') 
— •0187 sin (5a+274° 54') + '0083 sin (6fl!+323° 08') 
— •0098 sin (7a + 52° 26') + -0076 sin (8u+19° 06') 
-•0023 sin (9a+334° 32 ') + -0015 sin (10a+323° 08') 
-•0100 sin (lla+274° 44') -'0025 cos 12a. 
This formula gives for the times of extreme westerly deflection 2 ^ 52” and 13^^ 21”, 
the amounts being 12"-8 and l4"-9; and for the times of extreme easterly deflection 
S'* 0” and 19“ 30”, the amounts being 4"-3 and 6"-7. The means of the two times 
of westerly elongation are 2“ 06”-5 and 14“ 06”'5, and of the amounts, 13"'85. The 
means of the two times of easterly elongation are 7^^ 45” and 19“ 45”, and of the 
amounts, 5"-5. The total range of the lunar variation is (13"'85+5"'5^)19 '3o 
The times at which the deflection due to the moon’s action is 0 are 5“ 27®, 9 06”, 
17 “ 05” and 22“ 09”. These times taken in pairs are equidistant flora two points 
on the moon’s hour-circle, of which one is 1“ 48” after her upper culmination, and 
the other is l'' 05”-5 after her lower culmination. 
General Remarks.— yVe learn from the results which have been thus stated, that 
the existence of a lunar diurnal variation in the magnetic declination is shown at 
each of the three stations, Toronto, St. Helena, and Hobarton, and that it has the 
same general character at each, viz. that of a double progression m the lunar day 
with two easterly maxima at nearly opposite points of the hour-circle, and two westei ly 
maxima also at nearly opposite points of the hour-circle. The extreme elongations in 
the one direction are not at precisely opposite points of the hour-circle at any o e 
three stations, nor have the amounts of the two elongations, which take place m t e 
same direction, always precisely the same value, but the slight inequalities m diese 
respects are within the limits which might be occasioned by accidental irregularities. 
It is otherwise, however, with the difference in amount between the easterly and west- 
erly deflections, which exhibit at each of the three stations a disparity too great to be 
ascribed to accident. At Hobarton and St. Helena the westerly elongations have 
the largest values, and at Toronto the easterly (speaking always of the north end of 
the magnet). At Toronto and St. Helena the lesser elongations are about two-diirds 
of the amount of the larger ; at Hobarton the disparity is still greater ; to obtain the 
exact proportions with a sufficient degree of assurance would require, no doubt, a 
longer period of observation. ^ 
The difference which presents itself at the different stations, m the times o le 
occurrence of the extreme easterly and westerly elongations of the variation, is a very 
important feature in its bearing on the questions which must arise in regard to t e 
