706 
CAPTAIN F. W. BEECHEY ON THE TIDAL STREAMS OF 
Channel 
stream. 
Stream 
slacks at 
nearly the 
same time 
throughout, 
Simultane- 
ous turn of 
the stream. 
Time of high 
water at 
Dover, and 
the time of 
the turn of 
the stream 
compared. 
moment to ride with their heads in opposite directions, in obedience to the streams 
which were then running opposite ways. 
The Channel stream, which I have described as running between the intermediate 
stream and the rotatory or mixed streams at the outer extremities of the Channel, 
pursues a steady course along the main trunk of the strait, slacking only towards 
high and low water at Dover, when it is preparing to invert its course ; and contrary 
to the generally received opinion of a 'progressive slack water in a strait having a 
progressive establishment, this stream has the peculiarity of slacking throughout its 
whole extent at nearly the same time, and this time, as was anticipated in my former 
paper, corresponds nearly with the time of high and low water on the shore at Dover, 
the site of the combined wave and of the virtual head of the tide. 
Such is a general description of the phenomena of the streams of the English 
Channel and the North Sea ; and I shall now endeavour to describe more in detail the 
several peculiarities of these features, and to remove various erroneous impressions 
which at present exist as to the rotatory motion of our tides, the direction in which 
the streams turn, and also as to the time of the stream attaining its maximum rate, 
&c., and then to lay before you such data as it appears to me will help to explain the 
cause of the tidal streams of these channels dilfering from those peculiar to ordinary 
tide-waves. 
As the simultaneous turn of the stream is a point of considerable interest, I may 
be permitted to dwell a few minutes upon the data from which it has been derived. 
But I wish it to be clearly understood, that minute accuracy on such a point is scarcely 
possible, and could only be obtained by a long series of simultaneous observations 
at the extremities of the tide-wave ; for the period of slack water is almost always 
spread over an interval of half an hour, and not unfrequently at the neaps, of an hour 
and upwards ; and moreover winds are found to prolong the stream in the Channel 
according to the direction in which they blow. In estimating the time of slack water 
therefore from the observations, we must not expect a very close agreement^. 
It will be seen, on a very cursory inspection of the Charts which accompany 
this paper, that for a period of six hours after high water at Dover, and for five 
hours before that time, the stream maintains a steady direction from and towards 
Dover, so that any delay which may exist between the change of the stream and 
the time of high water is shown by these charts alone to be confined within very 
narrow limits, but a still closer agreement will be found on referring to the ob- 
servations themselves*; especially if w’e take those which were made on board the 
light- vessels at a distance from the shore, which are particularly valuable from the 
circumstance of their being spread over intervals of several days at each station. 
* The times of observed slack water at the stations marked in the Plans, as compared with the times of 
corresponding high waters at Dover, as shown by the tide tables, together with all other particulars relating to 
these observations, will be found entered in a book which accompanies this report, since deposited at the Hy- 
drographic Office of the Admiralty. 
