THE NORTH SEA AND ENGLISH CHANNEL. 
705 
water a rotatory motion, and scarcely admitting- of any interval of slack water ; Rotatory 
whilst in the space between these rotatory tides and the point of meeting- of the xrueChannel 
tides in the Strait of Dover, the stream is free from all rotatory motion, and sets stream, 
steadily throughout the tide in a direetion towards Dover, while the water is rising 
there and away from it while it falling at that place. 
I have designated the last-mentioned the true channel stream^' and its extent is, Extentofthe 
1 
as nearly as it can be measured, 180 miles in either direction from the point of union stream 
of the tides in the Strait of Dover to the region of rotatory tides off Lynn, and off the 
Start and St. Malo. 
As the true Channel streams are always running in opposite courses, there is neces- Meet in the 
sarily a point where they meet and separate ; and this occurs in the Strait of Dover. of 
But in this strait, the stream, although it first obeys one tide and then the other, 
does not slack with the Channel streams, but is found to be still running at high and 
low water on the shore, at which times those streams are at rest, so that the Strait of 
Dover never has slack water throughout its whole extent at any time. I have in Intermediate 
consequence called this an inter-mediate tide. 
The limits of neither of these streams appear to be stationary, but range to and fro 
as the tide rises and falls at Dover, travelling to the eastward on both tides, and at piace of 
high and low water suddenly shifting sixty miles to the westward to recommence 
their easterly courses with the next tide; and although so far apart, they possess changes with 
the remarkable peculiarity of shifting together ; so that the Channel streams preserve, 
as nearly as possible, the same relative dimensions. 
In the Strait of Dover this line of meeting and of separation oscillates between Peculiarity 
Beachy Head and the North Foreland, a distance of about sixty miles. When the pf the stream 
J)over 
water on the shore at Dover begins to fall, a separation of the Channel streams begins Strait, 
off Beachy Head. As the fall continues, this line creeps to the eastward. At two 
hours after high water it has reached Hastings ; at three hours Rye ; and thus it 
travels on until at low water, by the shore, it has arrived nearly at the North Fore- 
land on one side of the strait, and at Dunkirk on the other. At this time the Cha 72 nel 
streams on both sides slack, but in that portion which I call the intermediate stream 
in the Strait of Dover the water is still running to the westward ; and when the new 
Channel streams make as the water rises on the shore, this intermediate portion is 
found to unite with, or to oppose one or the other of these streams, according as it 
was before the reverse ; so that, as before mentioned, the line of meeting at low water 
appears off Beachy Head to recommence its easterly course. This intermediate 
stream forms a remarkable feature in the tidal system of the Channel ; it is well 
established, as the line of meeting and of separation occupies a very limited space, 
and it seems to be entirely due to the contracted form of the Channel in this imme- 
diate locality, preventing the free escape of the water. 
Captain Bullock, in order to test the point of separation, anchored two vessels a 
mile apart between Beachy Head and Dungeness, and found both vessels at the same 
