32 
mi. (4. I. TAYLOR ON TIDAL FRICTION IN THE IRISH SEA. 
Similarly on the dowii-chaiinel side, CD, of the cape, the time of H.W. will be 
made earlier by this local pecnliarity. 
When .r is negative and when — < - a decrease in a and an increase in h leads 
cl 2 
to an increase in —C, i.e., to a decrease in the time of H.W. Similarly, on the down- 
channel face of the cape, H.W. is made late by the cape. 
There are two interesting examples of this on the S.E. coast (.)f Ireland. One is 
at Wicklow Head. This is situated in the region where .r is positive. We shoidd, 
therefore, expect it to be H.W. later on the northern side of the cape than on the 
southern side. It is H.W. at Wicklow, a few miles N. of the cape at 10'53, 
2li. 3()m. later than H.W. at Arklow, some 11 miles south of the cape. Tliis 
effect evidently appeal’s to make the co-tidal line travel very slowly past Wicklow 
Head. 
The other example is tliat of Greenore Point. In tliis case x is negative, we should 
tlierefore expect the effect of the coast line to he to make the time of H.W. earlier 
on the north side of the cape than on the southern side. 
This effect might, if it were sufficiently great, reverse the direction of travel of tlie 
co-tidal line in the neighbourhood of the point. As a matter of fact the effect 
is great enough to do this. It is H.W. at Saltees, some 10 miles S.W. of Carnsore 
Point, at 6h. (im. At Carnsoi'e Point, 4 mile's 8. of Greenore Point, it is H.W. at 
6h. 25in. At Tuskar Rock. 4 miles out from Greenore Point, it is H.W. at 6h. 10m. 
At Wexford South Bay. on the north side of the Point, it is H.W. at 6h. 5m. After 
that the time of H.W. gets later as one goes further northwards up the coast. It 
will be seen that from Carnsore Point to Wexford South Bay, therefore, the direction 
of travel of the co-tidal line is just reversed. The fact that H.W. at Wexford South 
Bay, whicli is well round Greenore Point, is actually earlier than H.W. at Tuskar 
Rock which is south of Greenore Point, besides being 4 miles out at sea, is remark¬ 
able. I do not know whether any explanation has been offered before of how it is 
that the effect of a cape on the tidal phenomena in its neighbourhood is so very 
different in different parts of tlie sea. 
Sumrna)'!/ of Couchisicnis. {Added Octoher 1019.) 
The rate f)f dissipation of energy at spring tides in the Irish Sea is calculated from 
the known fonmdae for skin-friction of the Avind on the ground and the friction of 
riA’ers on their beds. The results range from 1040 to 1300 ergs per square centimetre 
per second. The least of these is 150 times as great as Mr. Street’s previous 
estimate of 7 ergs per square centimetre })er second. 
The rate at which energy flows into the Irish Sea is next calculated from the rise 
and tall of tide, the strength of the tidal current and their phase difference over two 
sections taken across tlie North and South Cliannels. The rate of dissipation of 
