210 THE SUBMARINE OP TO-DAY AND TO-MORROW.- 



Surface speed 14 knots. 



Surface fuel radius 2,490 miles. 



Submerged speed ii/4 knots. 



Submerged radius at 5 knots no miles. 



Armament 4 torpedo tubes and 4 torpedoes. 



The corresponding data for the later design are as follows : — 



Surface speed 14 knots. 



Surface fuel radius 3,150 miles. 



Submerged speed io>4 knots. 



Submerged radius at 5 knots 75 miles. 



Armaments 4 tubes, 8 torpedoes and one 3" gun. 



It will be noted that the newer design provides for slightly greater armament with 

 an increase in the surface radius. On the other hand, this has been compensated for 

 by a decrease in the submerged speed and radius. Notwithstanding this reduction in 

 submerged qualities, the surface displacement is increased 60 per cent. In this 

 particular case, there is no material difference in the weight and space per horse- 

 power of the main engines, and the very large increase in displacement has nearly all 

 been absorbed by habitability and safety features. 



The substantial influence of the type of main engines employed may also be 

 best illustrated by an example from actual practice. In the case in mind, on a sur- 

 face displacement of 350 tons, a trial speed of about I4>4 knots was obtained with 

 comparatively light two-cycle engines developing 450 horse-power at 450 revolutions 

 per minute. The engines in this case weighed about 56 pounds per horse-power. 

 When these engines were replaced by a heavy type weighing 86 pounds per horse- 

 power and operating at 375 revolutions per minute, the trial speed was reduced to 13 

 knots. 



Having thus briefly reviewed the main elements of the problem, we are now in a 

 position to consider the probabilities with respect to the characteristics of the United 

 States submarines of the near future. Let us consider first the question of the de- 

 fense type. Adequate defense obviously requires the assembly of the requisite num- 

 ber of boats where and at the time needed. Broadly speaking, this may be accom- 

 plished in two different ways. The first method is in principle that of local defense 

 embodying the permanent stationing of an adequate number of boats of moderate 

 radius in each locality where protection is desired. With adequate numbers, this 

 method can certainly be relied upon to prevent blockades, bombardments or landing 

 operations. The second method involves abandoning altogether the idea of assign- 

 ing groups of submarines for the defense of certain areas and using instead flotillas 

 of larger boats which by reason of increased speed and sea-keeping qualities could be 

 concentrated when and where wanted. Such flotillas could also carry the line of de- 

 fense much farther from the coast, and in this way could co-operate more fully with 



