1 50 Royal Society. 



tide at Jersey : that there is an increased rise there also ; and that 

 from the meeting of the tides off Lynn to the meeting of the streams 

 off Dover, there is, as in the former case, a stream which turns nearly 

 simultaneously with the high and low water on the shore at Dover ; 

 the incoming and outgoing streams coinciding with the rising and 

 falling water there ; and that there is, in fact, a complete identity of 

 tidal phenomena in both parts of the supposed canal ; of this an 

 illustration is given in two plans. 



The author states that the meeting of the waves which enter the 

 canal at opposite points does not occasion a stationary point of per- 

 manent slack-water, but one wave alternately prevails, so that the 

 point of slack- water oscillates between Ramsgate and Hastings nearly, 

 and occasions an inversion of the stream at about two hours before 

 that of the true stream of the channel. He thinks it convenient for 

 the purposes of navigation to consider this an intermediate stream, 

 although in reality it is only a shifting of the place of the meeting 

 and divergence of the opposite channel streams. To illustrate this 

 part of the paper a table is given, in which the courses of the streams 

 in various compartments of the supposed canal are given at every 

 hour of the tide. 



The author thinks this system of tides sufficiently established for 

 the purposes of navigation, but with regard to the perfectly simul- 

 taneous motion of the stream throughout the stationary wave, he is 

 of opinion that nothing but simultaneous observations will be con- 

 sidered satisfactory to science upon such a point, and these he hopes 

 will be supplied by the observations of the ensuing summer. 



The advantage of referring the motion of the stream to a standard 

 such as that of the Dover tide-table will, it appears, be sensibly felt 

 by the mariner, who will now have his course through the moving 

 waters of the channel rendered simple and plain, instead of being 

 perplexed with unsatisfactory references, and with calculations which 

 in too many instances, it is believed, have caused the set of the tide 

 to be wholly disregarded. 



The want of a standard to which desultory observations, made in 

 various parts of the channel, could be referred, the author believes 

 to have been the occasion of several erroneous impressions of a some- 

 what dangerous tendency to navigation. As such he considers the 

 following : — that the tide in all parts of the channel partakes of a 

 rotatory motion and is never at rest, and that a ship's reckoning will 

 never be far out in consequence, as she will never be carried far in 

 one direction : that a vessel arriving off the Start at low water 

 could, by sailing seven or eight knots an hour, carry ten or eleven 

 hours favourable tide to Beachy Head : that in the German Ocean 

 the stream sets north-east on one side, whilst it is running south- 

 west on the other : that there is a tide and half-tide in the channel, 

 so that when the stream has done in shore, by standing out, a ship 

 will carry the stream three hours longer, or nine hours in one direc- 

 tion : and lastly, that the stream runs strongest at high and low veater 

 throughout the channel, and is ujotionless at half-tide. 



These impressions do not appear to be justified by the observa- 



