210 THE OCEAN. 



considerable masses of water, situated at the base of tbe dunes, are 

 continually driven back into the interior. The rivers, arrested in 

 their course and changed into marshes, are also forced to retreat, and 

 mix their waters with those of the pools. This formation of lakes 

 and marshes, parallel to that of the dunes, is one of the most remark- 

 able features of the coast-line of the French Landes. A row of 

 ponds, differing in form and size, but all situated at a nearly equal 

 distance from the sea, is prolonged over a space of 125 miles. One 

 large bay, the basin of Arcachon, has been able to maintain a wide 

 communication with the ocean, owing perhaps to the river which it 

 receives from the interior. But all the other sheets of water, to the 

 north the etangs of Hourtin and Lacanau, and to the south those of 

 Cazau, Parentis, Aureilhan, St Julien, Leon, and Soustons, only 

 communicate with the sea by tortuous and rapid streams, and are now 

 at a level considerably higher than that of the sea. 



The etang of Cazau, the most elevated of all, and that which has 

 been driven gradually inland by the strongest dunes, spreads its 

 sheet of water at an altitude varj'ing from 63 to 66 feet, according 

 to the seasons. It has not less than 14,826 acres of mean superfi- 

 cies. The spectator who contemplates it from the top of a hillock 

 would think he saw a vast marine bay, for a great part of the op- 

 posite shores escape the eye, and the isolated trees which mark afar 

 off the distant bank, resemble a fleet of ships at anchor in a road ; 

 the white boulders of sand, of a triangular form, which are per- 

 ceived at the foot of the green dunes, and which appear like so many 

 sails of ships skimming along the coast, increase the illusion. Never- 

 theless, it is probable that the etang of Cazau was formerly a gulf 

 of the ocean, for the bottom of this small inland sea is still found to 

 be 36 feet below the marine level. The fishermen, who are the 

 best authorities in such matters, uniformly attest, that in the 

 lowest parts of the pond, the lead touches the sand at 15 fathoms. 

 They also assert that it formerly communicated by deep trenches 

 with the sea, and they even indicate the bay of Maubrucq as hav- 

 ing been the ancient port, and trace the direction followed by the 

 channel in the middle of the dunes. In the same way, the fisher' 

 men of the etang of Hourtin still show the site of the old port of 

 Anchise. 



It is easy to explain the gradual transformation of the ancient 

 Gulf of Cazau, and other marine bays which indented the now uni- 

 form coast of the Landes. Separated from the ocean at first by a 

 slender ridge of sand, as is often formed on low beaches, these bays 



