1866.] 



the West Coast of Scotland, 



45 



whicii pours through the openings, so that the tidal stream would be Httle 

 altered by building a dam from Islay to the Ross of Mull. 



The question may now be asked. Is the great X. to IV. stream which 

 has just been described a flood or an ebb tide? So far as regards the 

 Mull of Cantyre, Fairhead, and all that lies to the south or east, it is a true 

 ebb tide. So far as regards Jura, Scarba, and the coast to the north and 

 east, it is a true flood tide ; but as regards a great part of the region in 

 question, it cannot be called either a flood or an ebb tide, and much con- 

 fusion is occasioned io the Charts by attempting so to distinguish it. 



At the south end of Gigha in the Admiralty charts an arrow is laid 

 down, indicating that the flood tide runs to the northward ; and a few miles 

 south of this, another arrow is laid down, indicating that the flood tide runs 

 to the southward. From these arrows we might expect to find at this 

 place a meeting of the tide and a sudden change in the direction of the flood 

 stream. But the stream which is indicated by these arrows is nothing more 

 than the great X. to IV. northerly current which we have described. The 

 spot which is treated as a meeting of the tides, is merely that at which it is 

 high water at I. North of this, for more than three hours of the X. to IV. 

 stream, the tide is rising, and it is indicated as a flood tide. South for 

 more than three hours the tide is falling, and it is indicated as an ebb tide. 



On the south and west coast of Isla the confusion is greater. In some 

 of the charts, the incoming stream, is marked as the flood, in others, and 

 perhaps with better reason, the outgoing tide. It is in truth neither the 

 one nor the other. 



The extreme complication which arises from describing the time of change 

 of the stream by reference to the time of high and low water will now 

 appear ; thus we should have to say that in the Sound of Sanda, the ebb 

 stream begins two hours before high water ; at the Mull of Cantyre, one 

 hour before high water ; a little north of this again two hours before high 

 water. At the south of Gigha we might say indifl'erently, that the flood 

 tide runs to the south and begins three hours before low water, or that it 

 runs to the north and begins three hours after low water ; in the Sounds 

 of Islay and the Gulf of Corry Vreckan that it begins an hour before low 

 water ; and in describing the streams along the north coast of Ireland, we 

 have even greater complication. 



The direction of the tidal streams on the rest of the west coast of Scot- 

 land is easily described. The X. to IV. stream, through the course which 

 I have described, becomes an XI. to V. stream at the outside of Isla, and 

 through the Sound of lona. The stream which sets to the northward up 

 the Sound of Jura fills the Linnhe Loch, and causes high water at the south 

 end of the Sound of Mull at half-past V., whilst the high water caused by 

 the ocean tide at the north end of the Sound of Mull is an hour later ; 

 the consequence, as may easily be seen, is that nearly the whole flood tide 

 through the Sound of Mull runs to the northward, and the nearly whole 

 ebb tide runs to the southward. 



