296 THE REV. W. WHEWELL ON TIDE OBSERVATIONS 
remarked that we find an exemplification of such a case in the tides of the south coast 
of England, from the Isle of Wight to the Land’s End, as observed at the coast-guard 
stations in June 1834. At the period of writing that paper the observations of the 
south coast only had been reduced. I can now state that we have a much more re- 
markable example of the same fact in the tides on the east coast of Ireland. The 
rapid change of the tide-hour in passing round the northern and southern extremities 
of this coast is very remarkable, and may be seen in Tables III. and IV. Thus in 
passing round Rachlin Island and Fair Head, which form the north-eastern point of 
Ireland, through the narrow strait left by the Mull of Cantire, the tide-hour advances 
suddenly from 6^ h to 10^ h . In the same manner in passing round Carnsore Point, 
from the south to the east coast of the county of Wexford, the tide-hour advances 
from 5| h to 10| h , and ll h in a very short distance. 
Also when such hinges of the tide are once passed, the hour is nearly constant along 
the whole of the coast, as we have seen that it ought to be from general considera- 
tions. Thus all the way from Arklow in the south to Glenarm and Larne in the 
north of the eastern side of Ireland, the tide-hour at exposed points of the coast is 
from 10^ h to ll h ; and a little later in bights, as the Bay of Dublin and the mouth of 
the Boyne. The “ meeting of the tides” may be considered as extending over the 
whole of this space. In like manner, as I have already stated*, the sea from the 
Isle of Wight to the Downs is affected (at least as to its tide-hour) both by the 
channel tide and by that of the German Ocean. Hence the cotidal lines in such 
cases will cease to extend across the channel, and will become nearly parallel to the 
shore, as we see the 10 h line on the east coast of Ireland, and the 10 h line on the 
south coast of England. The lines assume this form by the successive hour-lines 
projecting more and more in the middle of the channel, as an ellipse may become two 
parallel lines by retaining its minor axis, and increasing its major axis indefinitely. 
16. There is another very curious circumstance connected with these cases of the 
meeting of tides. In those parts where the tide-hour increases most rapidly (or in 
other words where the tide-wave travels most slowly) the times of high water are 
subject to extreme irregularities. This is remarkably seen in the curves which I 
have used to represent the observations of such places. The lines for Rachlin Island, 
Ballycastle, Ballintoy, exhibit the most extraordinary irregularities in their course 
both in June 1834 and 1835. The greatest and least lunitidal intervals at Rachlin 
Island in June 1835 differ by no less than Jive hours and a half ; and there are in- 
stances of this interval differing two hours and a half in two successive tides. This 
appears to be partly due to the effect of the diurnal inequality of which we shall 
have to speak, but still it shows how liable the tide at this place is to the influence 
of irregularities. And I may observe that this peculiarity in the tides of this place 
explains the apparent inconsistencies which I formerly noticed in the statements 
* Philosophical Transactions, 1835, Part I. p. 89. 
