366 SAND-PLAINS OF BELGIUM. [March 



of the sand is also pushed beyond the usual high-water mark. In 

 the Baltic it is sometimes so raised to a height of between three and 

 four feet. A strong and long-continued west wind, which, in the 

 winter of 1824-1825, so raised the waters of the Baltic and of the 

 Gulf of Finland that the greater part of St. Petersburg was laid 

 imder water, carried the high tide on the Prussian coast of the 

 Baltic to a height of six feet ; and on the west coast of the island of 

 Sylt, and of the Frisean Islands in the German Ocean lying to the 

 west of Schleswig, the low water fell short of the usual ebb by 

 about the same measure. In such cases, when the sea returns to 

 its visual level, there remains beyond the reach of the waves a 

 portion of the sand borne landward in the time of the storm ; and 

 this becoming dry, becomes in this state the sport of the winds." 



Wessely goes on to say : " As such storms occur periodically, the 

 dash of the waves brings up more and more new masses of drift-sand ; 

 and by this not only is illustrated the process of sand-movements 

 occurring on the level strand of the sea, but there is made manifest 

 the great essential difference between the inland stretches of drift- 

 sand and those of the sea-coast. 



" The former has to do with a given mass of sand, which, once 

 fixed, belongs to drift-sand land formation ; the latter stretches 

 back upon an expanse which is now being more and more fed with 

 new material, where also the formation of the sand knows no end, 

 as the wide sea seems more likely to lose entirely its volume of sand." 



Fully to realize the difference thus indicated, we must cast a 

 retrospective glance on these facts : first, that the waves, in accord- 

 ance with hydraulic laws, always fall perpendicularly upon the shore, 

 and follow also the direction of the wind ; and second, that occasional 

 storms agitate the sea to a greater depth. The former explains the 

 uniform march of the dash of the waves ; the second combines with 

 the interrupted conveyance of new material by rivers and the 

 abrasion of the sea-shore, to prevent the withdrawal of the existing 

 sand deposits on the strand. 



If it be further borne in mind that the source of the sand never can 

 be stopped up, and that the sea-breeze is stronger and more violent 

 than is the land wind, then will it be seen that the coast land sand- 

 drifts, if left unchecked, must now be forming more and more 

 extensive wastes than the inland sands. 



Herr Wessely adds that " phenomena similar to what occur on the 

 sea-coast, but on a much less extensive scale, may sometimes 

 be seen on the shores of fresh-water lakes, and even on those 

 of rivers, in proportion as they may have a flat shore, and as the 

 former contain sand in their basin, or the latter bring it with them 

 in their flow. 



