SUBMARINE VESSELS 



solely by electric power, have little buoyancy, and do 

 very little running at the surface. The term "submer- 

 sible" is applied to a submarine boat, actuated by elec- 

 tricity while submerged, but using gasohne motors for 

 motive power while running at the surface. These 

 gasoline engines are used at the same time for charg- 

 ing the storage batteries; so that the submersible is a 

 much more practical boat than the submarine, and at 

 the same time is quite as good a diver. Indeed, al- 

 though many naval writers are very careful to make 

 a distinction in the use of these terms, there seems little 

 need of doing so, since only one type of boat — the 

 submersible — is now considered practical. But as the 

 word submarine is the older and more popular, it is 

 used here to cover both classes except in specific cases. 



For several years there were two classes of sub- 

 marines under observation — those possessing no float- 

 ability when submerged, and those having some 

 reserve buoyancy. The advantage claimed for the no- 

 floatability class of boats is that, having no buoyancy, 

 they are kept more easily at a certain depth below the 

 surface of the water instead of tending to come to the 

 surface constantly as in the case of boats of the other 

 type. 



But in actual practice the theoretical possibilities of 

 such boats have not come up to the expectations of 

 their advocates. For keeping the boat at a uniform 

 depth, the most universally accepted method is by the 

 use of horizontal rudders. The fact that the vertical 

 direction of a boat may be controlled by horizontal 

 rudders, when her buoyancy is small, has long since 



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