On leaving Arles, the train takes the bit between its teeth and races over the crau, straight as an arrow, between lines of cypresses. It is just possible to catch glimpses to the north, between the cypresses, of a chain of hills of opalescent hue. That chain, Les Alpines, gives its direction to the Durance. This river lent its aid to Brother Rhone to form this rubble plain, the Campus lapideus of the Romans, the modern crau. This was a desert over which the mirage alternated with the Mistral, till Adam de Craponne, in the sixteenth century, brought a canal from the Durance to water the stony land, and since then, little by little, the desert is being reclaimed. This vast stony plain was a puzzle to the ancients, and Æschylus, who flourished B.C. 472, tells us that Heracles, arriving at this plain to fight the Ligurians, and being without weapons, Heaven came to his aid and poured down great stones out of the sky against his foes. This is much like the account in Joshua of the battle against the Kings in the plain of Esdraelon.
At length, at Miramas, we escape from between the espalier cypresses and see that the distant chain has drawn nearer, that it has lost its mother-of-pearl tints, and has assumed a ghastly whiteness. Then we dash among these cretaceous rocks, desolate, forbidding and dead. They will attend us from Marseilles to Toulon.
The cretaceous sea bed, that once occupied so vast an area, has been lifted into downs and mountains, and stretched from Dorset and Wiltshire to Dover. We catch a glimpse of it at Amiens. A nodule that has defied erosion sustains the town and cathedral of Laon. It underlies the Champagne country. It asserts itself sullenly and resolutely in Provence, where it overlies the Jura limestone, and is almost indistinguishable from it at the junction, for it has the same inclination, the same fossils, and the same mineralogical constituents.
In England we are accustomed to the soft skin of thymy turf that covers the chalk on our downs. Of this there is none in Provence. The fierce sun forbids it. Consequently the rock is naked and cadaverously white, but scantily sprinkled over with stunted pines.
The Jura limestone is the great pièce de resistance in Provence: it is sweeter in colour than the chalk, ranging from cream white to buff and salmon; it has not the dead pallor of the chalk. Any one who has gone down the Cañon of the Tarn knows what exquisite gradations and harmonies of tone are to be found in Jura limestone. Here this formation stands up as a wall to the North, a mighty screen, sheltering the Riviera from the boreal winds. It rises precipitously to a plateau that is bald and desolate, but which is rent by ravines of great majesty and beauty, through which rush the waters from the snowy Alps. The chalk and the limestone are fissured, and allow the water flowing over their surface to filter down and issue forth in the valleys, rendering these fertile and green, whereas the plateaux are bare. The plateaux rise to the height of 3,000 or 4,500 feet.
The tract between the mountain wall of limestone and the sea is made up of a molass of rolled fragments of the rock in a paste of mud. This forms hills of considerable height, and this also is sawn through here and there by rills, or washed out by rivers.
Altogether different in character is the mass of the Montagnes des Maures, which is an uplifted body of granite and schist.
Altogether different again is the Estérel, a protruded region of red porphyry.
About these protruded masses may be seen the new red sandstone.
When we have mastered this—and it is simple enough to remember—we know the character of the geology from the mouths of the Rhone to Albenga.