CHAPTER V. THE CRAU.
The Basin of Berre - A neglected harbour - The diluvium - Formation of the Crau - The two Craus - Canal of Craponne - Climate of the Crau - The Bise and Mistral - Force of the wind - Cypresses - A vision of kobolds.
On leaving Marseilles by train for Arles, the line cuts through the limestone ridge of the Estaque, and the traveller passes from the basin of Marseilles into the much more extensive basin of Berre, surrounded by hills on all sides, a wide bowl like a volcanic crater, with the great inland salt lake of the Etang de Berre occupying its depths. This is a great natural harbour, seven times the size of the port of Toulon, and varying in depth from 28 to 32 feet; it is perfectly sheltered from every wind, and entire fleets might anchor there in security, not only out of reach, but out of sight of an enemy, for the chain of l'Estaque intervenes between it and the sea. It would seem as though Nature herself had designed Berre as a safe harbour for the merchant vessels that visit the south coast of France. It is almost inconceivable how this sheet of water, communicating with the sea by the channel of Martignes, can have been neglected; how it is that its still blue waters are not crowded with ships, and its smiling shores not studded with a chain of industrial and populous towns. "The neglect of this little inland sea as a port of refuge," says M. Elisee Reclus, "is an economic scandal. Whilst on dangerous coasts harbours are constructed at vast expense, here we have one that is perfect, and which has been neglected for fifteen centuries." But though the Romans or Greeks had a station here, they did not utilise the lagoon. At S. Chamas are remains of the masters of the ancient world, but no evidence that they had there a naval station.
The line cuts again through the lip of the basin, and we are in the Crau.
At a remote period, but, nevertheless, in one geologically modern, the vast floods of the diluvial age that flowed from the Alps brought down incredible quantities of rolled stones, the detritus of the Alps. This filled up a great bay now occupied by the mouths of the Rhone, and spread in a triangle from Avignon as the apex, to Cette in the west, and Fos in the east. This rubble, washed down from the Alps, forms the substratum of the immense plain that inclines at a very slight angle into the Mediterranean, and extends for a considerable distance below the sea. Not only did the Rhone bring down these boulders, but also the Durance, which enters the Rhone above Arles, and formed between the chain of Les Alpines and the Luberon another triangular plain of rolled stones, with the apex at Cavaillon and the base between Tarascon and Avignon. But the Durance did more. There is a break in the chain on the south, between the limestone Alpines and the sandstone Trevaresse; and the brimming Durance, unable to discharge all her water, choked with rubble, into the Rhone, burst through the open door or natural waste-pipe, by Salon, and carried a portion of her pebbles into the sea directly, without asking her sister the Rhone to help her. Now the two great plains formed by the delta of the Rhone, and that of the Durance into the Rhone, are called the great and little Craus. They were known to the ancients, and puzzled them not a little. Strabo says of the Great Crau: "Between Marseilles and the mouth of the Rhone, at about a hundred stadia from the sea, is a plain, circular in form, and a hundred stadia in diameter, to which a singular event obtained for it the name of the Field of Pebbles. It is, in fact, covered with pebbles, as big as the fist, among which grows some grass in sufficient abundance to pasture herds of oxen."
Then we are given the legend that accounts for it. Here Hercules fought against the Ligurians, when the son of Jove, having exhausted his arrows, was supplied with artillery by a discharge of stones from the sky, showered on his enemies by Jupiter.
This desert, a little Sahara in Europe, occupies 30,000 acres. "It is composed entirely of shingle," says Arthur Young, "being so uniform a mass of round stones, some to the size of a man's head, but of all sizes less, that the newly thrown up shingle of a seashore is hardly less free from soil; beneath these surface-stones is not so much a sand as a cemented rubble, with a small admixture of loam. Vegetation is rare and miserable, some of the absinthium and lavender so low and poor as scarcely to be recognised, and two or three miserable grasses, with Centaurea calycitropes and solstitialis, were the principal plants I could find." A mineralogical examination of the rolled stones presents peculiar interest. In the Little Crau, the mouth of the Durance, are found prodigious numbers of green and crystalline rocks, granite and variolite brought down from the Alps of Briancon, but nine-tenths of the pebbles of the Great Crau are white quartz brought from the great chain of the Alps, together with mica-slate and calcareous stones, and only a few of the variolites of Mont Genevre. One may say that the Great Crau is a complete mineralogical collection of all the rocks that form the chain of the Alps, whence flow the Rhone and its tributaries.