232 THE WORLD. 



sea in the thirteenth century, and the formation of a strait of 

 about half the width of the English channel in 100 years, lends 

 countenance to this opinion. The inroads of the sea have no 

 where been more severe than in Holland, and even at the pres- 

 ent day 12,000 wind-mills are employed to drain the Netherlands 

 and to prevent at least two-thirds of the kingdom from returning 

 to the state of bog and morass, and during the past year three 

 immense steam engines, capable of discharging 2,800,000 tons 

 of water in 24 hours, have been employed in pumping out and 

 emptying through the great ship canal, and sea-sluices at Katwyk, 

 the lake of Haarlem, which by its continual inroads threatened to 

 inundate Amsterdam on the one side, and Leyden on the other. 

 In the year 1836, twenty-nine thousand acres of land were com- 

 pletely overflowed by it. The large lake called the Bies Bach 

 was formed in 1621, by the sea bursting through the embank- 

 ments of the river Meuse, overflowing seventy-two villages. Of 

 these villages no vestiges of thirty-five of them were ever dis- 

 covered. Since their destruction an alluvial deposit has been 

 formed parti:,' over their site. The island of Northstraud, which 

 in the year 1634, contained 9000 inhabitants, and was celebra- 

 ted for its high state of cultivation, was, on the evening of the 

 llth of October, in that year, swept away by a flood which de- 

 stroyed 1300 houses, 50,000 head of cattle, and 6000 men, leav- 

 ing three small islets, one of them still called Northstrand, which 

 are continually being wasted away by the sea. Such are some of 

 the powerful effects of currents and waves in altering, and finally 

 sweeping away the headlands and islands which at any particular 

 epoch may have distinguished the line^of coast exposed to their 

 force; the eastern side of America, along the Atlantic coast is 

 subject to the same changes. Before leaving this part of our 

 subject, we will describe that peculiar tidal wave called " the 

 Bore." This is produced, when the channel of a river, into 

 which the tidal wave from the ocean is entering, is so narrow that 

 the water is made to rise suddenly, and thus terminates abruptly 

 on the side away from the sea, or inland ; precisely like the waves 

 which break upon a shelving shore. As might be expected, this 

 phenomenon occurs most powerfully at the time of spring, or high- 



