MR. G. I. TAYLOR ON TIDAL FRICTION IN THE IRISH SEA. 
17 
AB runs in a direction N. 86° E., while the current runs in a direction N. 26° E., 
so that 0 — 60° and sin 0 = 0'87. 
T = 12Ah., Ti = 8h. lOm., = 8h. 20in. 
so that 
Ti-To = lOm. = 
and 
cos y(Ti-T,) = cos ( g ^^^ 2 - 4 ) 
D == 37 fathoms = 6800 cm. 
Hj = 4|- feet = 145 cm. 
L = 50 nautical miles = 9'1 x 10® cm. 
Hence the mean rate at which energy is transmitted across the section AB is 
Wat = ix 98i X r03x 163 X 0-87 x TO x 6800 x 145 x 91 x 10® 
= 6'4 X 10^^ ergs per second.(24) 
North Channel. —The same method may be applied to the North C^hannel, but it 
is at once obvious that practically no energy entei's the Irish Sea through this 
channel. The tidal streams set strongly through the North Channel, running in 
from 5h. to llh. and out from llh. to 5li. at full and change of the moon. The neck 
between the Mull of Clntyre and the Irish Coast forms a loop in a stationar}^ 
oscillation. It is H.W. at Mull of Cantyre at lOh. 58m. At Red Bay, on the Irisli 
Coast, it is H.W. at lOh. 55m. The co-tidal line for lOh. 55m., therefore, runs from 
the Mull of Cantyre to Red Bay, and it is for this reason that it has been chosen for 
the section RC (see fig. 3) along which the integral for Wkc (the energy which flows 
across RC) will be taken. Since the streams cliange direction at H. W., Dover, i.e., at 
llh. 7m., the phase difference between the tidal stream and the height of the tide is 
only 12m. of time short of the quarter period, i.e., 87° expressed as an angle. 
The maximum current runs through the North Channel at a rate of 4 knots. The 
rise and fall ot' tide in the North Channel is very small ; at Red Bay it is 4 feet, and 
at Ballycastle Bay, to the N.W. of Red Bay, it is only 3 feet. At the Mull of 
Cantyre it is also 4 feet. The equality of tlie heights of tlie tide on the two sides of 
the channel is probably due to the fact that, at the times the stream is running at its 
maximum speed, when therefore we shoidd expect the maximum difference in level on 
the two sides of the Channel owing to geostrophic force, the water is at its mean 
level. At H.W. and L.W. the streams are slack, so that no geostrophic effect is to be 
anticipated at those times. 
In the formula 
WKc = /3f/cos 6 cos ^ (To-T\)x (length of RC) . . . (25) 
^ JL 
VOL. GCXX.— A. 
D 
