714 
CAPTAIN F. W. BEECHEY ON THE TIDAL STREAMS OF 
Powerful in- 
fluence of 
the combined 
w'ave over 
the streams 
of the 
Channel. 
Streams of 
the Irish 
Channel 
under a simi- 
lar influence. 
This wave is not, however, of sufBeient magnitude to affect the streams which tra- 
verse its surface, which seem to be under the entire control of the combined wave. 
The inverse order of the establishments upon the coast of Belgium and of Holland is 
a point of considerable interest, and I greatly regret that the season has been so un- 
favourable that no observations have been made which throw any additional light 
upon the subject. 
If we place the mean water-level of the middle sections of the wave together, we 
shall form the figures traced in Plan 2, Plate XLL, and shall be struck with the very 
small limits off Harwich through which the large wave at Dover is transmitted; this 
contracted portion of the sketch is nearly in the situation in which Professor 
Whewell has drawn the node of the North Sea tides. 
I'he influence of the combined wave over the tidal phenomena of the channels 
on both sides of the Strait of Dover is very remarkable. The streams of both 
it will be seen reverse together as the wave is matured ; they extend to the same 
distance from the apex of the wave, where they are met by rotatory streams ; in 
short, the whole tidal feature of one-half of the strait bears so close a resemblance 
to that of the other as to leave no doubt of their being both due to a common 
impulse. For instance, it may be seen in the Plans which accompany this report, 
that in the North Sea the streams of the oceanic and Channel wave meet off the 
estuary of Lynn, as they do off the estuary of St. Malo in the English Channel, at 
the same hours and at the same distances nearly from the head of the combined 
wave ; that there is an increased rise of the tide at Lynn as in the Gulf of St. Malo, 
although not to the same extent, owing perhaps to a different conformation of coast, 
but sufficiently large to establish the similitude, being in both cases nearly double 
that of the offing rise ; that in these localities, on both sides, the streams are all of a 
rotatory character, and that from the meeting of the streams off Lynn to the meeting 
of the streams off Dover, there is, as in the English Channel, from the meeting of the 
streams off St. Malo, to the meeting of the aforesaid streams off Dover, a stream 
which flows steadily on both sides towards Dover, whilst the water is rising at that 
place and sets away from it, whilst the water is falling there ; each portion having 
the remarkable peculiarity of reversing its stream throughout nearly simultaneously 
with the time at which the combined wave is matured. 
I may here observe, that in this respect the Irish Channel is precisely under the 
same circumstances as the English Channel and North Sea. The tide-wave enters 
that sea in like manner by opposite routes, and forms one vast wave, having all the 
peculiarities of a combined wave. On each side of the apex of this wave the streams 
reverse throughout at nearly the same time; that time corresponding with the time 
at which the combined wave is perfected, as occurs with the streams in the English 
Channel. 
In the Irish Channel the streams are even more regular than those of the North 
Sea and English Channel, and suffer less disturbance from the ocean or offing streams. 
It is true that in the Irish Sea there is no intermediate stream where the tides meet. 
