260 RECENT FORMATIONS. 



drifted inland, and piled up in fringes of dunes or hillocks 

 beyond the reach of the waves. By this process, continued 

 year after year, and century after century, the sea is gra- 

 dually banked back, and large sandy tracts created, terres- 

 trial and wind-blown above, but marine and water-drifted 

 below. We once watched the sinking of a well in the 

 sandy tract that stretches between St Andrews and the Tay 

 (Pilmoor and Tentsmoor Links) : the first fifteen or twenty 

 feet were through wind-blown sands and thin layers of 

 vegetable soil ; the remainder, to a great depth, was through 

 masses of sand, shells, gravel, and shingle, the drift of St 

 Andrews Bay when its waves rolled several miles farther 

 inland than they do now. As with this instance so with 

 others, whether along the shores of Holland, the Landes of 

 Biscay, or the Bights of Western Australia. These sand- 

 dunes, from narrow fringes of a few acres to rolling ex- 

 panses of many square miles in extent, may be witnessed 

 along the seaboard of every region, one of the most strik- 

 ing examples in Europe being the "Landes de Bour- 

 deaux " (stretching southward from the mouth of the 

 Garonne along the Bay of Biscay, and onwards towards 

 Bourdeaux), with their shifting sandhills along shore, their 

 dense forests of sea-pine farther inland, and beyond these 

 artificially planted shelters vast expanses of heathy undu- 

 lating sheep-runs. 



In addition to these littoral silts and pelagic sediments, 

 there is another class of marine deposits which have of late 

 years much engaged the attention of geologists, partly from 

 their varying and vast antiquity, and partly from the evi- 

 dence they afford of repeated elevations of the land. We 

 refer to those " raised beaches " or " ancient sea-margins," 

 whose terrace-like flats are found fringing the seaboard of 

 almost every region. Were our own islands to be upraised 

 to the extent of twenty or thirty feet, the present shores 



