CHARACTER OF DUNE SAND. 567 
structure of the dunes, observation has proved that it is nearly 
identical with that of submerged sand banks.* The differences 
of form are generally ascribable to the greater number and 
variety of surface accidents of the ground on which the sand 
hills of the land are built up, and to the more frequent changes, 
and wider variety of direction, in the courses of the wind. 
Character of Dune Sand. 
“Dune sand,” says Staring, “ consists of well-rounded grains 
of quartz, more or less colored by iron, and often mingled with 
fragments of shells, small indeed, but still visible to the naked 
eye.+ These fragments are not constant constituents of dune 
* Forchhammer ascribes the resemblance between the furrowing of the dune 
sands and the beach ripples, not to the similarity of the effect of wind and 
water upon sand, but wholly to the action of the wind; in the first instance, 
directly, in the latter, through the water. ‘‘ The wind-ripples on the surface 
of the dunes precisely resemble the water-ripples of sand flats occasionally 
overflowed by the sea; and with the closest scrutiny, I have never been able 
to detect the slightest difference between them. This is easily explained by 
the fact, that the water-ripples are produced by the action of light wind on 
the water which only transmits the air-waves to the sand.”—LEONHARD und 
Bronn, 1841, pp. 7, 8. 
+ According to the French authorities, the dunes of France are not always 
composed of quartzose sand. ‘‘ The dune sands” of different characters, says 
Brémontier, ‘‘ partake of the nature of the different materials 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.”— Mémoire sur les Dunes, Annales des Ponts et Chaussées, t. 
vii., 1833, ler sémestre, 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. 
Fraas informs us, Aus dem Orient, pp. 176, 177, that the dune sands of the 
Egyptian coast arise from the disintegration of the calcareous sandstone of the 
same region. This sandstone, composed in a large proportion of detritus of 
both land and sea shells mingled with quartz sand, appears to have been con- 
solidated under water during an ancient period of subsidence. A later up- 
heayal brought it to or near the surface, when it was more or less disintegra- 
