44 



Mr. A. Smith on the Tidal Currerds on [Mar. 8, 



I may observe that an analogous symbol may be used to express the 

 mere complicated tides which occur where different streams meet. Thus 

 near the Eddystone the stream may be expressed by a symbol of this kind : — 





















y 











the bearing and distance of the centre of the diagram from any numeral 

 indicating the direction and rate of stream at that hour. 



The time of high and low water in the region which we are considering 

 may be thus described. Near the two extremities, viz. the Giant's Cause- 

 way and the Island of Eysdill, the time of high water at full and change is 

 nearly Greenwich time, being very nearly that due to the Great Atlantic 

 tidal wave propagated from S.W. to N.E., and the same is very nearly 

 the hour of high water on the chain of islands of which Isla, Jura and 

 Scarba are the chief. But along the coast of the mainland of Ireland and 

 Scotland the case is very different. Between these two countries is the 

 great opening into the Liverpool basin, in which it is high water about XI. 

 The change in the time of high water takes place by the following grada- 

 tions : — At Giant's Causeway it is high water about VI., at Ballycastle VIL, 

 Torpoint X., Mull of Cantyre XL, Gigha XL, Loch Killispoint IV., Eys- 

 dill and Scarba V, Jura and Islay V|. But while the hour of high water 

 varies, the stream through nearN the whole of the region runs from X. to 

 IV. in one direction and from IV. to X. in the other. 



Between the Mull of Cantyre and the N.E. coast of Ireland, the X. to 

 IV. stream runs to the north. 



The most westerly part turns to the west, and runs through the Sound 

 of Rathlin along the north coast of Ireland ; the central part flows to the 

 N.W. past the Rhynns of Islay ; the easterly part, which has flowed partly 

 through the Sound of Sanda, turns sharply round the Mull of Canfyre, 

 and flows to the northward, pouring with great velocity through the nar- 

 row openings in the chain of islands, viz., the Sound of Islay between Islay 

 and Jura, the Gulf of Corry Vreckan between Jura and Scarba, the little 

 Corry Vreckan between Scarba and Lunga, the Slate Isles and the Cuan 

 Sound ; of these the little Corry Vreckan is quite impassable ; and Corry 

 Vreckan and the Cuan Sound are seldom attempted except near slack 

 mter. 



These channels open into the basin which lies between Jura and lona — 

 a comparatively tideless sea, owing apparently to the circumstance of the 

 ocean tide from the outside of Isla rising to nearly the same height as that 



