rOEMATIOX OF MAEINE CALCAEEOUS ROCKS. 183 



of seaweed and anlraalcul£e, mixed witli sand and clay, are deposited 

 in deep layers on the coast, and cause the outline of the shores to ad- 

 vance gradually. Mud has been accumulated by hundreds and tens of 

 thousands of millions of cubic yards since the historical era in the 

 ancient Gulf of Poitou, in the Gulf of Carentan, situated at the foot 

 of the peninsula of the Cotentin, in the bays of the Marquenterre 

 and of Flanders, in certain estuaries of the Netherlands and of Fries- 

 land. In these parts the sea and the land are mingled ; the sea, gray 

 or yellowish, resembles an immense slough, and continues th^ oozy 

 surface of the shores ; one does not know where the water ter- 

 minates, or where the plain of mud, incessantly stirred by the tidal 

 wave, begins. Still the mud which emerges at low water is, little by 

 little, heaped up and consolidated ; a species of conferva covers its 

 surface with a slight carpeting of a pink hue ; then come the herba- 

 ceous salicornia, which contribute to elevate the soil by their stiff 

 branches springing from the stem at right angles. To this first 

 vegetation succeed other marine plants — carices, plantains, reeds, 

 and climbing trefoil. Then is the time to recover the oozy meadow 

 for agriculture, and to connect it with the mainland by defending it 

 with strong dikes against the assaults of the sea.* 



In the seas whose waters have a high average temperature, the 

 waves do not confine themselves to constructing littoral ridges and 

 filling up the bays ; they even build actual ramparts of stone. In 

 consequence of the rapid evaporation produced by the rays of the 

 sun, the calcareous particles and mud contained in the water are 

 gradually deposited along the shores and over the base of the 

 promontories. Mixed with sand and fragments of shells, it tends 

 to form solid shores with regular contours. On the Atlantic 

 coasts of France, at Hoyan for example, one can, here and there, 

 already observe some formations of this kind ; and further to 

 the north, at Elsinore, some of these stones have been discovered, 

 containing ancient Danish coins.f On the French shores of the 

 Mediterranean these modern rocks are very numerous, and in a short 

 walk one can often collect a large quantity of sandy blocks and 

 various conglomerates, united by calcareous substances, and con- 

 taining multitudes of broken shells. The Museum of Montpellier 

 possesses a cannon which was discovered near the principal 

 mouth of the Ehone, imbedded in a calcareous deposit. On the 



* Emile de Laveleye, Itevue des Deux Mondes, Nov. 1, 1863. Von Maack, Zeitschrift 

 fur die allgemeine Erdkunde, Jan., 1860. 



t Von Hoff, Vermiderungen der Erdoherjldche, tome iii. p. 311. 



