Part 40 (1/2)

[435] American observers do not agree in their descriptions of the form and character of the sand grains which compose the interior dunes of the North American desert. C. C. Parry, geologist to the Mexican Boundary Commission, in describing the dunes near the station at a spring thirty-two miles west from the Rio Grande at El Paso, says: ”The separate grains of the sand composing the sand hills are seen under a lens to be angular, and not rounded, as would be the case in regular beach deposits.”--_U. S. Mexican Boundary Survey, Report of_, vol. i, _Geological Report of C. C. Parry_, p. 10.

In the general description of the country traversed, same volume, p. 47, 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 denote a difference of origin or of age.

[436] LAURENT (_Memoire sur le Sahara_, pp. 11, 12, and elsewhere) speaks of a funnel-shaped depression at a high point in the dunes, as a characteristic feature of the sand hills of the Algerian desert. This seems to be an approximation to the crescent form noticed by Meyen and Poppig in the inland dunes of Peru.

[437] _Travels in Peru_, New York, 1848, chap. ix.

[438] Notwithstanding the general tendency of isolated coast dunes and of the peaks of the sand ridges to a.s.sume a conical form, Andresen states that the hills of the inner or landward rows are sometimes _bow-shaped_, and sometimes undulating in outline.--_Om Klitformationen_, p. 84. He says further that: ”Before an obstruction, two or three feet high and considerably longer, lying perpendicularly to the direction of the wind, the sand is deposited with a windward angle of from 6 to 12, and the bank presents a concave face to the wind, while, behind the obstruction, the outline is convex;” and he lays it down as a general rule, that a slope, _from_ which sand is blown, is left with a concavity of about one inch of depth to four feet of distance; a slope, _upon_ which sand is dropped by the wind, is convex.

It appears from Andresen's figures, however, that the concavity and convexity referred to, apply, not to the _horizontal longitudinal_ section of the sand bank, as his language unexplained by the drawings might be supposed to mean, but to the _vertical cross-section_, and hence the dunes he describes, with the exception above noted, do not correspond to those of the American deserts.--_Om Klitformationen_, p.

86.

The dunes of Gascony, which sometimes exceed three hundred feet in height, present the same concavity and convexity of _vertical_ cross-section. The slopes of these dunes are much steeper than those of the Netherlands and the Danish coast; for while all observers agree in a.s.signing to the seaward and landward faces of those latter, respectively, angles of from 5 to 12, and 30 with the horizon, the corresponding faces of the dunes of Gascony present angles of from 10 to 25, and 50 to 60.--LAVAL, _Memoire sur les Dunes de Gascogne, Annales des Ponts et Chaussees_, 1847, 2me semestre.

[439] Krause, speaking of the dunes on the coast of Prussia, says: ”Their origin belongs to three different periods, in which important changes in the relative level of sea and land have unquestionably taken place. * * * Except in the deep depressions between them, the dunes are everywhere sprinkled, to a considerable height, with brown oxydulated iron, which has penetrated into the sand to the depth of from three to eighteen inches, and colored it red. * * * Above the iron is a stratum of sand differing in composition from ordinary sea sand, and on this, growing woods are always found. * * * The gradually acc.u.mulated forest soil occurs in beds of from one to three feet thick, and changes, proceeding upward, from gray sand to black humus.” Even on the third or seaward range, the sand gra.s.ses appear and thrive luxuriantly, at least on the west coast, though. Krause doubts whether the dunes of the east coast were ever thus protected.--_Der Dunenbau_, pp. 8, 11.

[440] LAVAL, _Memoire sur les Dunes de Gascogne, Annales des Ponts et Chaussees_, 1847, 2me semestre, p. 231. The same opinion had been expressed by BReMONTIER, _Annales des Ponts et Chaussees_, 1833, 1er semestre, p. 185.

[441] ”In the Middle Ages,” says Willibald Alexis, as quoted by Muller, _Das Buch der Pflanzenwelt_ i, p. 16, ”the Nehrung was extending itself further, and the narrow opening near Lochstadt had filled itself up with sand. A great pine forest bound with its roots the dune sand and the heath uninterruptedly from Danzig to Pillau. King Frederick William I was once in want of money. A certain Herr von Korff promised to procure it for him, without loan or taxes, if he could be allowed to remove something quite useless. He thinned out the forests of Prussia, which then, indeed, possessed little pecuniary value; but he felled the entire woods of the Frische Nehrung, so far as they lay within the Prussian territory. The financial operation was a success. The king had money, but in the elementary operation which resulted from it, the state received irreparable injury. The sea winds rush over the bared hills; the Frische Haff is half-choked with sand; the channel between Elbing, the sea, and Konigsberg is endangered, and the fisheries in the Haff injured. The operation of Herr von Korff brought the king 200,000 thalers. The state would now willingly expend millions to restore the forests again.”

[442] STARING, _Voormaals en Thans_, p. 231. Had the dunes of the Netherlandish and French coasts, at the period of the Roman invasion, resembled the moving sand hills of the present day, it is inconceivable that they could have escaped the notice of so acute a physical geographer as Strabo; and the absolute silence of Caesar, Ptolemy, and the encyclopaedic Pliny, respecting them, would be not less inexplicable.

The Old Northern language, the ancient tongue of Denmark, though rich in terms descriptive of natural scenery, had no name for dune, nor do I think the sand hills of the coast are anywhere noticed in Icelandic literature. The modern Icelanders, in treating of the dunes of Jutland, call them _klettr_, hill, cliff, and the Danish _klit_ is from that source. The word Dune is also of recent introduction into German. Had the dunes been distinguished from other hillocks, in ancient times, by so remarkable a feature as the propensity to drift, they would certainly have acquired a specific name in both Old Northern and German. So long as they were wooded knolls, they needed no peculiar name; when they became formidable, from the destruction of the woods which confined them, they acquired a designation.

[443] The sands of Cape Cod were partially, if not completely, covered with vegetation by nature. Dr. Dwight, describing the dunes as they were in 1800, says: ”Some of them are covered with beach gra.s.s; some fringed with whortleberry bushes; and some tufted with a small and singular growth of oaks. * * * The parts of this barrier, which are covered with whortleberry bushes and with oaks, have been either not at all, or very little blown. The oaks, particularly, appear to be the continuation of the forests originally formed on this spot. * * * They wore all the marks of extreme age; were, in some instances, already decayed, and in others decaying; were h.o.a.ry with moss, and were deformed by branches, broken and wasted, not by violence, but by time.”--_Travels_, iii, p.

91.

[444] Bergsoe (_Reventlovs Virksomhed_, ii, 3) states that the dunes on the west coast of Jutland were stationary before the destruction of the forests to the east of them. The felling of the tall trees removed the resistance to the lower currents of the westerly winds, and the sands have since buried a great extent of fertile soil. See also same work, ii, p. 124.

[445] ”We must, therefore, not be surprised to see the people here deal as gingerly with their dunes, as if treading among eggs. He who is lucky enough to own a molehill of dune pets it affectionately, and spends his substance in cheris.h.i.+ng and fattening it. That fair, fertile, rich province, the peninsula of Eiderstadt in the south of Friesland, has, on the point toward the sea, only a tiny row of dunes, some six miles long or so; but the people talk of their fringe of sand hills as if it were a border set with pearls. They look upon it as their best defence against Neptune. They have connected it with their system of dikes, and for years have kept sentries posted to protect it against wanton injury.”--J. G. KOHL, _Die Inseln u. Marschen Schleswig-Holsteins_, ii, p. 115.

[446] Sand banks sometimes connect themselves with the coast at both ends, and thus cut off a portion of the sea. In this case, as well as when salt water is enclosed by sea dikes, the water thus separated from the ocean gradually becomes fresh, or at least brackish. The Haffs, or large expanses of fresh water in Eastern Prussia--which are divided from the Baltic by narrow sand banks called Nehrungen, or, at sheltered points of the coast, by fluviatile deposits called Werders--all have one or more open pa.s.sages, through which the water of the rivers that supply them at last finds its way to the sea.

[447] ANDRESEN, _Om Klitformationen_, pp. 68-72.

[448] Id., pp. 231, 232. Andresen's work, though printed in 1861, was finished in 1859. Lyell (_Antiquity of Man_, 1863, p. 14) says: ”Even in the course of the present century, the salt waters have made one eruption into the Baltic by the Liimfjord, although they have been now again excluded.”

[449] FORCHHAMMER, _Geognostische Studien am Meeres-Ufer_. LEONHARD und BRONN, _Jahrbuch_, 1841, pp. 11, 13.

[450] ANDRESEN, _Om Klitformationen_, pp. 68, 72.

[451] _Voormaals en Thans_, pp. 126, 170.

[452] See a very interesting article ent.i.tled ”Le Littoral de la France,” by eLISeE RECLUS, in the _Revue des Deux Mondes_, for December, 1862, pp. 901, 936.