FISHING-GROUNDS 55 



lit by the light of the sun, so that it is covered by 

 abundant growths of marine plants. The sediments 

 which cover it are of mud, sand, gravel, and pebbles ; 

 the dust carried by the winds is deposited upon it, and 

 it receives the alluvial burden of the rivers. The action 

 of the waves, which affects it to an average depth of 

 25 fathoms, divides it into two regions : the coastal or 

 in-shore region, which is often disturbed by the over- 

 lying waters, and the off-shore region, where a greater 

 calm prevails. The former is subject to almost daily 

 changes of temperature, and the bottom is irregular and 

 varied. In the latter region the floor is generally level 

 and the temperature more constant. 



The in-shore region comprises the space between 

 the extreme tide-marks and such parts as are always 

 submerged by not more than 25 fathoms ; it embraces 

 rocks, reefs, and islands. The rocks, as a rule, become 

 smaller as the depth becomes greater, while the algae 

 which clothe them become longer. The sandy beaches 

 are succeeded by the " meadows " of sea-grasses mono- 

 cotyledons of the Zostera family which in turn are 

 succeeded by the Bryozoarian deposits and conch if erous 

 debris. The in-shore region comprises by definition 

 all the articulations of the coast : capes, bays, estuaries, 

 lagoons, and salt-water ponds. Mud is predominant, 

 more or less mingled with sand, and the sea-meadows 

 of the Armorican peninsula are choked with it. The 

 bay of the Seine, which is from 9 to 25 fathoms 

 in depth, is a marvellous trawling-ground. Of the 

 salt-water ponds and lagoons I will here mention only 

 that of Arcachon. According to my friend M. Camille 

 Mader, who knows it better than any one, this little 

 inland sea of 37,000 acres (58 square miles) is simply 

 the ancient estuary of the Leyre. The mud is slowly 



