POETS EEMAEKABLE FOE HIGH TIDES. 



109 



Similar phenomena occur in the two bays of Mount St. Michael 

 and the Severn. There, too, rivers and rivulets are periodically- 

 changed into gulfs ; there, too, the harbours are tidal ports, where 

 ships, with the exception of those which are enclosed within the basins, 

 lie on their sides in sand or mud at the time of low water. In the 

 same way the space extending between I^oirmoutiers and the coast of 



it'io' West 



4<'30'W. 



Depth indicated in feet 

 Fig. 37. — Sti'aits of Noirraoutiers. 



La Yendee is alternately an isthmus and a strait; a high road traversed 

 by vehicles winds through the sandy plain between pools of water, 



