MADE ON THE COASTS OF EUROPE AND AMERICA IN JUNE 1835. 295 
diate places being as late as 2^ b ; and in the Bay of Biscay the hour at Santander is 
later than at Bilboa, though the latter place is further east. 
In Ireland the 4^ h line runs along the whole coast of Munster, touching it in many 
places, and the 5 h line runs along the remaining west and south coast of the island 
at no great distance. 
12. Another circumstance which I may notice in the corrected form of these lines, 
and which results from the same tendency, is, that the hour-lines which are earlier 
than the littoral ones spread over the general surface of the ocean more widely, and 
catch the projecting points of land sooner, than had been supposed. Thus the line 
of 10§ h nearly touches Cape Hatteras on the coast of America, and compels us to 
extend the 10 h and ll h lines considerably to the west. 
13. We may observe also that this expansion of the oceanic and compression of 
the intervals of the littoral cotidal lines, necessarily give an extremely complex form 
to the former, since they must in some degree accommodate themselves to all the 
land which surrounds them. Thus, as we have seen, the 10^ h hour-line nearly touches 
Cape Hatteras. It also extends from the eastern to the western coast of the Atlantic. 
But its course must be very sinuous, for the vulgar establishment at the Bermudas is 
7 h 18 m *, which places the 1 l h cotidal line nearly there. In these and similar cases 
it is probable that there are, as I have formerly suggested, “ detached spaces within 
which the tides are later than in the surrounding seas, occupied by converging rings 
or loops of cotidal lines.” 
14. As there are large tracts of coast along which the tide-hour exhibits no steady 
progression, there are, on the other hand, points where it changes very rapidly. 
These are generally promontories. Thus on the coast of America we have a rapid 
change in passing round the projection formed by Nantucket and other islands. On 
the coast of France, in passing round Cape La Hague and Barfleur, the tide-hour 
advances from 6 h to 9 h . In the same manner on the opposite coast of England the 
7 h and 8 h cotidal lines both touch St. Alban’s Head in Dorsetshire, and the 9 h and 10 h 
lines both touch St. Catherine’s Point in the Isle of Wight. The tide in passing 
round the north coast of Scotland and the Orkneys appears to undergo a compara- 
tively rapid increase of the establishment from about 6 h on the western to 12 h on the 
eastern coast. 
15. But the most rapid of the changes which thus occur in passing round promon- 
tories are those which are accompanied by a meeting of tides, arriving in opposite 
directions along two different channels ; as the tides on the east coast of Ireland, 
which arrive both from the north and from the south ; and the tides in the eastern 
part of the English Channel, which are derived through the Straits as well as up the 
Channel. I have already remarked that two tide-waves travelling in opposite direc- 
tions along the same channel will make the tide-hour nearly constant along a con- 
siderable tract of coast, while it varies rapidly at the extremities of this tract-f-. I 
* Philosophical Transactions, 1833, Part I. p. 172. t Ibid. 1835, Part I. p. 87. 
