32 MR. G. I. TAYLOR ON TIDAL FRICTION IN THE IRISH SEA. 



Similarly on the down-channel side, CD, of the cape, the time of H.W. will be 

 made earlier by this local peculiarity. 



When x is negative and when ^- < ^ a decrease in a and an increase in b leads 



to an increase in t z , 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 of Ireland. One is 

 at Wicklow Head. This is situated in the region where x is positive. We should, 

 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, 

 2h. 30m. later than H.W. at Arklow, some 11 miles south of the cape. This 

 effect evidently appears to make the co-tidal line travel very slowly past Wicklow 

 Head. 



The other example is that of Greenore Point. In this case x is negative, we should 

 therefore expect the effect of the coast line to be 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 the 

 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 Oh. Om. At Carnsore Point, 4 miles S. of Greenore Point, it is H.W. at 

 Gli. 25m. 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. which 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. 1 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 the sea. 



Summary of Conclusions. (Added October 44, 1919.} 



The rate of dissipation of energy at spring tides in the Irish Sea is calculated from 

 the known formulae for skin-friction of the wind on the ground and the friction of 

 rivers 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 per second. 



The rate at which energy flows into the Irish Sea is next calculated from the rise 

 and fall of tide, the strength of the tidal current and their phase difference over two 

 sections taken across the North and South Channels. The rate of dissipation of 



