94 THE BOTTOM OF TEE SEA. 



If the sea struggles victoriously against the laud 

 when the latter opposes to it some formidable ob- 

 stacle, its efforts fail, its force, so to speak, expires 

 when there is no such resistance. It batters down 

 the rock-bound shore with resistless force ; it flows 

 harmlessly over low and sandy flats. Further, the 

 debris of the stubborn rock serves to strengthen the 

 shifting sands, and to renew the dunes which the 

 winds scatter in light clouds of dust. The tidal wave 

 spreads out over the level shore, until it has lost 

 all its speed, and when it retires it leaves behind it 

 on the sands all the materials which it had pushed 

 before it as it came in from the sea. 



3. Deposits in Mid-ocean, and Deposits on the Coasts — Importance 

 to Geologists of Coast Deposits as data for fixing the limits of 

 Ancient Seas — Deposits of the French Seas. 



It is only from a large number of skilful soundings 

 that we have been able to ascertain the character ot 

 submarine deposits. Soundings at great depths 

 generally indicate the presence of the debris of rocks 

 in a state of minute subdivision. To take a single 

 example : at a point seventy leagues south of the 

 Aleutian Isles, and at a depth of 9000 feet, we detect 

 the presence of fine sand and mud. 



The deeper parts of the ocean occur at too great 

 a distance from the coasts for the larger and heavier 



