AECTIC SEAS. — PAET VI. POET KENNEDY. 
347 
The Diurnal Tide is represented by the formula 
D = S' sin 2a cos (s— i s ) + M 7 cos 2^ cos(m — i m ), (2) 
where the letters have the meaning stated in my former papers, viz. — 
S', M 7 the Solar and Lunar coefficients uncorrected for Parallax ; 
o', (jj the declinations of the Sun and Moon at an interval preceding the observation 
called the Age of the Tide ; 
s, m the Solar and Lunar Hour-angles at the time of observation ; 
i s , i m the true Solitidal and Lunitidal Diurnal Intervals. 
The Lunar Tide vanishes when ^=0 ; and this corresponds with Table III., which 
contains the Maximum value of the apparent Solitidal Interval not influenced by the 
Moon, but representing the full effect of the Sun. 
The Moon’s declination vanished twice : 
From N. to S. at 5 d 5 h ll m , and 
From S. to N. at 19 d 17 h 14 m , 
which correspond fairly with the times of Maximum retardation of Solidiurnal Interval. 
The age of the Lunidiurnal Tide may be found from the interval between the Moon’s 
declination vanishing and the Lunar Tide vanishing, as shown by the Maximum value 
of the Solitidal Interval. From the first time of tide vanishing we have 
d h m 
5 22 46 
6 5 0 
6 17 0 
7 10 26 
Mean=6 13 48 
^=0 at 5 5 11 
Age of Lunar Diurnal Tide . . . .1 6 37 
From second time of tide vanishing we have 
18 18 0 
18 23 45 
19 5 40 
19 11 0 
Mean=19 2 36 
^=0 at 19 17 14 
Age of Lunar Diurnal Tide . . . 00 14 38 
From Table III. it appears that the value of i s , the true Diurnal Solitidal Interval, is 
?;=5 h 12 m 7| s (3) 
The Minimum values of the apparent Solitidal Intervals, caused by the Maximum 
influence of the Lunar Tide, are contained in Table IV. 
