between High-water and Slack-water, V ' 185 



channel ; but as far as I am aware, no attempt was made to give a 

 satisfactory explanation of these phsenomena until the publication, 

 by the present Astronomer Royal, of the article on Tides and Waves 

 in the Encyclopedia Metropolitana. In that article, very ingenious 

 explanations of many of the phsenomena in question are given 

 from the analytical results of most unpromising hypotheses, — 

 hypotheses admitted to be so much at variance with the real 

 state of things, that the coincidence of the results is very extra- 

 ordinary and unexpected. Though undoubtedly these results 

 would take place on the hypotheses alluded to, I now venture to 

 offer another explanation of the same, or of some of the same 

 phsenomena, founded upon considerations which I have been 

 unable to reconcile with the above-mentioned hypotheses. They 

 may, however, hereafter be reconciled, and it will be very sin- 

 gular if they cannot, and if it should turn out that two inde- 

 pendent causes produce the same result ; for it can hardly be 

 doubted that the actions explained in this paper do really take 

 place, and nrdst produce some effect on the tidal motions. 



Explanation of Tide and Half -tide. 



Let us suppose A to be an estuary or the open sea, in which 

 the tide rises and falls alter- 

 nately and uniformly 13 feet 

 in six hours, this assump- 

 tion being made for the sake 

 of simplicity. Let R be a 

 reservoir or inland sea in 

 communication with A by 

 the channel C, and of inde- 

 finite size, i, e. so large that 

 the quantity of water flow- 

 ing through C in six hours 

 does not perceptibly affect 

 the general level in R; it is then obvious that in time the 

 water in R will attain the mean level of the water in A, i. e. 6 

 feet above low- water mark in A. Let us now suppose it low 

 water in A at 0^; the stream will then be ebbing out of R 

 through C with the velocity due to the fall of 6 feet : as the 

 tide in A rises the water in C will rise, but will continue to ebb 

 from R through C till the water in A attains its mean height 

 of 6 feet, which will be at 3^. The stream will then turn 

 and begin to flow through C into R, rising at the same time 

 till 6^, when it will be high water in A; the water in A will 

 then begin to fall, but will continue to flow into R till 9^, 

 when the water in A attains its mean level; the stream will then 

 turn in C and ebb, the water falling at the same time till 12^, 



