DIVING IN MOBILE BAY. 



673 



and satisfied himself of their condition, and that he could 

 recover some of them entire and others in parts. In this 

 work use was made of an enormous pump, raising nearly 1,000 

 tons of water a minute. With this, after closing as well as 

 could be, the port holes and other openings, another pipe for 

 the introduction of air was arranged, and the pump set in 

 action. This powerful machine emptied the vessel of water 

 in a very short time, so that the air flowed into it by the other 

 pipe, and the vessel rose of itself to the surface. An enormous 

 chain, each link of which weighed over two hundred pounds, 

 was used to help lift them, when necessary, or alone when it 

 was found most easy to use alone. 



CAULKING A VESSEL. 



A very important use to which the submarine armor is 

 often put, is that of enabling the diver to clean the bottom of a 

 vessel, below water, while she is moving. This is a great con 

 venience, as it saves the delay and expense of being obliged 

 to place her in a dry dock. A rope ladder, with rungs of wood 

 or iron, is stretched under the ship, passing down one side 

 and up the other. It is thus drawn tight, and the diver de 



