4T4 
CHARACTER OF DUNE SAND. 
others blown over or between them, build up a second row of 
dunes, and so on according to the character of the wind, the 
supply and consistence of the sand, and the face of the country. 
In this way is formed a belt of sand dunes, irregularly dis¬ 
persed and varying much in height and dimensions, and some¬ 
times many miles in breadth. On the Island of Sylt, in the 
German Sea, where there are several rows, the width of the 
belt is from half a mile to a mile. There are similar ranges 
on the coast of Holland, exceeding two miles in breadth, while 
at the mouths of the Nile they form a zone not less than ten 
miles wide. The base of some of the dunes in the Delta of 
the Nile is reached by the river during the annual inundation, 
and the infiltration of the water, which contains lime, has con¬ 
verted the lower strata into a silicious limestone, or rather a 
calcareous sandstone, and thus afforded an opportunity of 
studying the structure of that rock in a locality where its 
origin and mode of aggregation and solidification are known. 
Character of Dune Sand. 
“ Dune sand,” says Staring, “ consists of well-rounded 
grains of quartz, more or less colored by iron, and often min¬ 
gled with fragments of shells, small indeed, but still visible to 
the naked eye.* These fragments are not constant constit¬ 
uents of dune sand. They are sometimes found at the very 
summits of the hillocks, as at Overveen; in the King’s Dune, 
* According to the French authorities, the dunes of France are not 
always composed of quartzose sand. “ The dune sands ” of different 
characters, says Br6montier, “ partake of the nature of the different mate¬ 
rials which compose them. At certain points on the coast of Normandy 
they are found to be purely calcareous; they are of mixed composition on 
the shores of Brittany and Saintonge, and generally quartzose between the 
mouth of the Gironde and that of the Adour.”— Memoire sur les Dunes , 
Annates des Pouts et Ghaussees , t. vii, 1833, ler s6mestre, p. 146. 
In the dunes of Long Island and of Jutland, there are considerable 
veins composed almost wholly of garnet. For a very full examination of 
the mechanical and chemical composition of the dune sands of Jutland, see 
Andresen, Om Klitformationen , p. 110. 
