HARMONIC ANALYSIS OF TIDAL OBSERVATIONS. 97 
the evaluation of the diurnal tides have been chosen, and the reason for 
the choice, alleged in the Report to the British Association for 1872, 
seems to be to minimise the effect of the M,-tide on the diurnal tide, 
The period intended to be chosen (for the arithmetic seems to have been 
incorrectly worked out). will, it is true, minimise the effect of the M,-tide ; 
the M,-tide is, however, so small that it appears to the writer that there 
was no advantage gained by the choice. 
The computation forms show the following periods. 
[L.] 
Periods over which the Harmonie Analysis extends in the several series of 
Tides of Short Period. 
Tide Period in § days Period in special days 
d h d h 
s 369 3 . 369 3 
XN 369 3 . 396 15 
O 369 3 . 343 3 
K 369 3 . 370 3 
P 369 3 . 368 3 
J 370 5 . 384 16 
Q 370 5 » S80uL7 
L 369 3) 363 8) 
or 358 «~6) or 352 15] 
N gel 6 aaa 349 22 
or 3858 6) or 339 15} 
r . 849 22) 343 14 
or 369 3) or 362 t0| 
v 349 22) 332 14 
or 369 3) or 350 20} 
por 2MS 569 3 3443 
R : 369 38 369 15 
4h : 369 3 368 15 
jis ae 369 3 362 21 
28M . 369 3 381 15 
The computation forms for the L, N, X, v tides have been drawn up 
in alternative forms, so that the computer may stop at the shorter period 
if desirable. 
It is proposed to drop the reduction of the tides \ and R, and to add 
certain new tides which have been denoted 2N, MK,2MK. ‘These last 
have been made to extend over a period of 36993". This period was chosen 
because if we put ,)=2(y—c), 1.=2(y—n), we have ny—n,;=2(a—n) ; 
and 369% 35 11™ is equal to 25 periods of an angular velocity 2(¢—7). 
Again, if we put n,=2y—30+a or 2y—a—a, and ny=2(y—c) we 
have m.—m, or m,—7, equal to o—a@; and 3584 54 1™ js equal to 13 
periods of an angular velocity s—az. The 3587 6" which occurs in the 
computation forms is a mistake for 358% 5h, 
Next, if we put ny =2y—30—a@ +2» or2y—0+ a —2n, and n,=2(y—c) 
we have m.—2, or n;—n, equal to 2(o—n)—(o~az); and 349% 22h Q]m 
is equal to 11 periods of an angular velocity ¢+a—2n. 
Lastly, if we put n}=y—30+a@ or y+o—za, and ny=y—c we have 
My-—N, OY Ny—N equal to 2z—a; and 370" 9 46™ is equal to 27 periods 
of an angular velocity 2s—a. The 370° 5 which occurs in the compnta- 
tion forms is a mistake for 370° 10». 
18838. H 
