819 



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

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

 dency somewhat dangerous 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 water 

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



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

 tions. The stream, when not diverted by rivers or estuaries, appears 

 to run true up and down the channel, and from side to side nearly ; 

 between the Start and Hastings, in the English Channel, scarcely 

 varying a point for nearly five hours ; and in the German Ocean for 

 about four hours ; the varying of the stream there being due, in the 

 author's opinion, to the influence of the Thames and the rivers of 

 Holland. As the stream turns nearly with the high and low water 

 on the shore at Dover, there cannot be nine hours' current in one 

 direction. With regard to the time at which the stream attains its 

 greatest strength, he states that all the observations agree in fixing 

 it at about half-tide (Dover). 



The erroneous impressions above mentioned, the author considers 

 have arisen from the times of the observations when made having 

 been referred to the times of high water at places differing two or 

 three hours from the time of high water at the head of the wave, or 

 from an early popular opinion that the turn of the stream in the 

 offing coincides with the rise and fall of the water on the shore. 



The paper concludes with some remarks on the forms of the tide- 

 wave between Cromarty and the Land's End, which are exhibited in 

 two plans at every hour of the tide, obtained from a combination of 

 the ranges and establishments of Dr. Whewell with those of M. 

 Chazallon ; and attention is particularly drawn to the relative lengths 

 of the stationary wave and the waves by which it is generated ; the 

 former wave being only half the dimensions of the latter. These forms 

 are exhibited on a reduced scale, but much exaggerated in height, 

 and aff'ord a comparison between the curve assumed by the stationary 

 wave and that which the waves would have assumed had they rolled 

 on in an uninterrupted course. 



His Grace the Lord».Archbishop of Canterbury, and the Right 

 Honourable Lord John Russell, were admitted into the Society on 

 January 25, 184'9. 



2 



