278 THE BOTTOM OF THE SEA. 



machine has already been put to the test. The port 

 of Fecamp was choke I up with shingle, which closed 

 it against all vessels beyond a certain tonnage. The 

 hydrostat was emplo3^ed, and the port cleaned and 

 again opened to commerce. The cases in which it 

 might be employed with advantage are obviously 

 very numerous. 



Ports are more generally made by digging vast 

 basins in the neighbourhood of coasts than by seeking 

 to enclose portions of the sea by means of jetties. 

 The work is more easily and quickly done in the 

 open air, and there is not the probability that the sea 

 will overturn it at any moment. The port enclosed 

 by hills, or the natural port, has the double advantage 

 of giving shelter both against wind and wave. But if 

 the port fill up gradually, if its mouth become 

 obstructed by mud or sand washel up by the sea, 

 the hydrostat may be advantageously employed. 



9. Villeroy's Submarine Boat, 



What ingenuity has been brought to bear on the 

 construction of submarine engines, both for purposes 

 of destruction and investigation! Boats to sail be- 

 neath the water, diving-bells and dresses, submarine 

 fireships and torpedoes, are all so many evidences of 

 the activity developed in the human mind by the sea. 



