* Royal Society. 319 



servatlons, which are numerous, the author enters into an explana- 

 tion of the whole system of tidal streams in the English Channel and 

 North Sea, as deduced from these observations, and also as to what 

 he considers to be the cause of the peculiar movement of the streams 

 in these channels. He supposes, in conformity with Dr. Whewell's 

 theory, a tide-wave to pass along the western shores of Europe, and 

 to enter the English Channel and North Sea by opposite routes, and 

 to arrive off the Texel and Lynn at the same tidal hour as the tide- 

 wave in the English Channel arrives off the Start and Jersey. 

 From these points there are thrown off branch or derivative waves, 

 which differ materially both in dimensions and rate of travelling from 

 the parent wave. These waves roll on towards the strait of Dover 

 and there merge into each other and form a combined wave. 



The effect of this wave upon the tidal establishments of the Chan- 

 nel had long been known ; but its influence upon the streams of the 

 Channel had never before been considered, nor had any observations 

 upon them been systematically undertaken. 



In arranging the plan of observation the author considered that, 

 as the combined wave was common to both the English Channel 

 and North Sea, the tidal streams of both these channels would be 

 found to correspond in every important particular, and that the 

 movement of the streams throughout the strait would be materially 

 influenced, if not wholly governed, by the motion of the combined 

 wave ; that the time of this wave attaining its greatest altitude would 

 thus afford a standard to which the turn of the streams throughout 

 the Channel might be advantageously referred ; and that there would 

 be found in this Channel, as in the Irish Sea, which is equally under 

 the influence of a combined wave, a stream which would turn nearly 

 simultaneously throughout the strait with the times of higii and low 

 water on the shore at the point of combination or virtual head of 

 the tide. 



Accordingly the observations were conducted upon this plan, and 

 all the movements of the stream were referred to the time of high 

 water at Dover, which had been determined upon as the standard 

 from its being situated nearly at the point where the combined wave 

 is formed. It appeared from the intervals which this mode of com- 

 parison afforded, that whilst the water was rising at Dover, the 

 stream of the channels on both sides ran towards that place ; and on 

 the contrary, in the opposite direction whilst the water wsls falling 

 there ; and that these streams pursued a steady course throughout the 

 tide, and extended from a line joining the Texel and Lynn, in the 

 North Sea, to a line joining the Start and Jersey in the English 

 Channel. Beyond these limits the streams of the Channel were 

 found to encounter those of the offing or parent wave, and to occa- 

 sion the tides in those localities to partake of a rotatory character, 

 revolving for the most part with the sun, and having scarcely any 

 interval of slack water. 



The line of meeting of these streams was found not to be a sta- 

 tionary line, neither in those parts where the Channel-stream en- 

 counters the offing stream, nor where the streams meet in the strait 



Z2 



