ACCUMULATIONS OF SAND. 'Ml 



5. Littornl accurauLitions— Coast-line -Mtirine Lagoons and Pools - 

 Lagoons moved inland by the oUects of the Dunes in Gascouy — 

 Villages buried lionaith the Dunes near St. Pol-de-Le'on in 

 Brittany, and also in Guscouy — Bordeaux menaced. 



The elevation of a sliore by the addition of fresh 

 soil is effected by the sea-waves as well as by rivers. 

 Every coast exhibits, within the limits occupied by 

 the sea, a quantity of loose sand and rounded peb- 

 bles. The less rapid the current is at the bottom of 

 the sea, the slower is the accumulation, which, how- 

 ever, attains great importance on low coasts, giving 

 rise to dunes, bars, and a number of other phenomena, 

 which we shall indicate in a few words. 



We have seen that the mass of loose stones, &c. 

 thrown up by the sea at its borders, is continuous 

 along eveiy coast, and that it marks what is called the 

 coast-line. When formed of fine sand, and the soil 

 is not clayey, the action of the wind, in conjunction 

 with the waves, causes the production of those hills 

 of sand called dunes. 



Lagoons often accompany the coast-line if the shore 

 be clayey, and if the country be sufficiently flat to 

 allow the water to remain in any slight inequality 

 of the soil, or to flow very slowly towards the sea. 



Bars and other phenomena, the study of which 

 would carry us beyond our subject, in conjunction 



