INLAND DUNES. 601 
certain extent, cohesive by moisture and by the saline and 
other binding ingredients of sea-water, while long exposure to 
meteoric influences has in a great measure deprived the inland 
sands of these constituents, though there are not wanting 
examples of large accumulations of sand far from the sea, and 
yet agglutinated by saline material. Hence, as might be ex- 
pected, inland dunes, when not confined by a fixed nucleus, are 
generally more movable than those of the coast, and the form 
of such dunes is more or less modified by their want of con- 
sistence. Thus, the crescent or falciform shape is described by 
all observers as more constant and conspicuous in these sand- 
hills than in those of littoral origin; they tend less to unite in 
continuous ridges, and they rarely attain the height or other di- 
mensions of the dunes of the seashore. 
Meyer describes the sand-hills of the Peruvian desert as 
perfectly falciform in shape and from seven to fifteen feet high, 
the chord of their arc measuring from twenty to seventy paces. 
The slope of the convex face is described as very small, that of 
the concave as high as 70° or 80°, and their surfaces were 
rippled. No smaller dunes were observed, nor any in the 
process of formation. The concave side uniformly faced the 
Colonel Emory says that on an ‘‘ examination of the sand with a microscope 
of sufficient power,” the grains are seen to be angular, not rounded by rolling 
in water. 
On the other hand, Blake, in Geological Report, Pacific Railroad Rep., vol. 
v., p. 119, observes that the grains of the dune sand, consisting of quartz, 
chalcedony, carnelian, agate, rose quartz, and probably chrysolite, were much 
rounded; and on page 241, he says that many of the sand grains of the 
Colorado desert are perfect spheres. 
On page 20 of a report in vol. ii. of the Pacific Railroad Report, by the same 
observer, it is said that an examination of dune sands brought from the Llano 
Estacado by Captain Pope, showed the grains to be ‘‘much rounded by 
attrition,” 
The sands described by Mr. Parry and Colonel Emory are not from the same 
localities as those examined by Mr. Blake, and the difference in their character 
may be due to a difference of origin or of age. 
In New Mexico, sixty miles south of Fort Stanton, there are inland dunes 
composed of finely granulated gypsum.—Americun Naturalist, Jan, 1871, 
p- 695. 
