MR. LUBBOCK ON THE TIDES IN THE PORT OF LONDON. 
391 
At the end of May l — 45° nearly, and then according to Table III. when 
the moon passes the meridian at 2, the interval between her transit and H. W. 
is l h 16 m nearly; when the moon passes the meridian at 8, the interval be- 
tween her transit and H. W. is l h 38 m nearly. The variation or difference being 
in the one case — 5 m , (l h 20 m — l h 25 m = — 5 m ), and in the other + 13 ,n , 
(l h 38 m — l h 25 m = + 13 m ). 
The formula gives in the one case 
and in the other 
tan (2 S y — 2 1,) = - C' 
tan (2 0, — 2 l,) 
- C 1 
m n 3 
according to which the variation or difference should be in both cases of the 
same sign : hence the variations or differences — 5 m and -f- 13 m are not owing 
to this inequality. 
It is possible that this discrepancy may be owing to the terms which have r ( 4 
in the denominator ; but the observations are made so carelessly that I shall 
not attempt to take these terms into consideration. 
The discrepancy which I have pointed out is sufficient to show that Table III. 
cannot be represented by the expression of p. 387, line 13, whatever value be 
given to the constants employed : this discrepancy is not confined to the epoch 
I have noticed, but extends throughout the year. 
Neglecting this discrepancy which not only prevents the expression above 
from representing the observations, but must also I think vitiate any conclu- 
sions to be drawn respecting the mass of the moon ; in April when 1=0, and 
when the moon passes the meridian at 5 h , the interval is 0 h 34 m 
11 2 14 
2 h I4 m — 34 m = l h 40 m 
I may suppose 
tan l h 40 m = tan 25° = 
o _ win 3 (1 + nx) . 2m l U l s 
“T 
sin* a; 
m ; n, 3 (l + »,*) mn 3 (1 + si ^,^ 
•4663 = -3788 + 
mn s 
2 m 
sin 2 w 
n, 3 . n / . sin 2 w\ 
' 0 2 J 
3 E 
MDCCCXXXI. 
