The lake or pool of Cazau is a small sea of fresh water, perfectly clear, profoundly deep, and fourteen to fifteen thousand acres in extent. It has its whirlwinds and its tempests, so that in certain seasons it is perilous to embark on its surface. And were its banks clothed with rich woods, or raised aloft in irregular or precipitous cliffs, it would surely attract as great a throng of tourists as the mountain-tarns and lochs of Scotland or Cumberland, or the Arcadian waters of Northern Italy. The lake of Biscarosse, in form a triangle, with one side formed by the Dunes, covers about twelve thousand acres. It derives its name from a village situated at its northern angle, on the bank of the canal which connects it with the lake of Cazau. The lake of Aureilhan is the smallest of the three; the St. Eulalie canal, which links it to the preceding, traverses a series of peat-bogs bounded eastward by gloomy pine-forests, and westward by the interminable Dunes, which, by arresting the flow of the rain-waters, have really created these so-called lakes and extensive swamps. Enormous quantities of rain fall every year in the Landes,—which district the Romans would certainly have dedicated to Jupiter Pluvius,—and find beneath the thin superficial stratum or crust of sand and earth, a sub-soil of tufa and allios—in other words, of compact chalk and sand agglutinated by a ferruginous sediment. Frequently this tufa possesses all the hardness of stone, and its imperviousness is its fundamental property. Hence it follows, that a portion of the heavy annual rainfall remains in the receptacles provided by the hollows and depressions of the soil, and in due time accumulates into marshes and lagoons, until gradually evaporated by the heat of spring.
When of old the scared peasants beheld the irresistible advance of these strange ministers of destruction, they had no other resource than to fell their woods, abandon their dwellings, and surrender their “little all” to the pitiless sand and devouring sea. What could avail against such a scourge? Efforts were made to repel it. It is said that Charlemagne, during a brief residence in the Landes, on his return from his expedition against the Saracens, employed his veterans, and expended large sums of money in preserving the cities of the coast from imminent ruin; but whether the means employed were insufficient, or whether the imperial resources failed, and other urgent needs diverted the population and their leaders from this struggle against nature, the works were wholly abandoned.
Of late years they have been resumed, and with greater success, by a skilful agriculturist, M. Desbiey, of Bordeaux, and an able engineer, M. Bremontier, who have called in nature herself to assist man in his war against nature. Their system consists of sowing in the driest sand the seeds of the sea-pine, mixed with those of the broom (genista scoparia), and the psamma arenaria. The spaces thus sown are then closely covered with branches to protect them from the action of the winds. These seeds germinate spontaneously. The brooms, which spring up rapidly, restrain the sand, while sheltering the young pines, and thenceforth the Dune ceases to move, because the wind can no longer unsettle its substance, and the grains are held together by the roots of the young plants. The work is always begun on the inland side, in order to protect the farmer and the peasant, and to withdraw the infant forest from the unwholesome influence of the ocean-winds. And, in order that the sown spaces shall not themselves be buried under the sands blown up from the shore, a palisade of wicker-work is raised at a suitable distance, which, reinforced by young plants of sandwort (psamma arenaria), check the moving sands for a sufficiently long time to favour the development of the seeds. Finally, the work is completed by the construction of a substantial wall, or rather an artificial cliff, which effectually prevents the further progress of the flood, or directs it seaward, to be arrested on its course by the barrier of the sand-hills. Unable to force a passage through these natural ramparts, they have excavated certain basins, more or less extensive, more or less deep, which have formed into inland seas, communicating with the Atlantic by one narrow issue.
It is a noteworthy fact that, owing to the encroachment of the Dunes, these lakes have been constantly forced back upon the inland country. Fortunately, this menacing invasion of the sands has been checked by the great engineering works executed a few years ago; which, on the one hand, have fixed, and, as it were, solidified the Dunes, and, on the other, have provided for the regular outflow of the waters. The Landes have thus been opened to the persevering labours of the cultivator. The culture of the pine, and the manufacture of resinous substances, have largely extended, and the time, perhaps, is not far distant when these deserts will almost completely disappear; when these desolate and unproductive plains will pleasantly bloom, transformed into shadowy woods or verdurous meadows.[10]
To so fortunate a result nothing will more powerfully contribute than the embankment of the Dunes. These have been, in reality, the true scourge of this country; these were the moving desert, the constantly ascending sea, which had already engulfed forests, villages, even towns, under its billows of sand, and driven before it the terrified inhabitants of the coast.
CHAPTER III.
THE DUNES, OR SAND-HILLS.
THE Dunes form the extreme line of the Brittany coast for nearly two hundred miles, from the Adour to the Garonne. They are hills of white sand, as fine and soft as if it had been sifted through an hour-glass. Their outline, therefore, changes every hour. When the wind blows from the land, millions of tons of sand are hourly driven into the sea, to be washed up again on the beach and blown inland by the first Biscay gale. A water hurricane from the west will fill up with sand square miles of shallow lake, driving the displaced waters into the interior, dispersing them in shining pools among the “murmurous pines,” flooding and frequently destroying the scattered hamlets of the people, and inundating their fields of rye and millet.[11]
