OF MEN-OF-WAR AND THEIR EMBODIMENT IN DESIGN. 77 



known practically. Theoretically it may be pointed out that the defensive strength measures 

 and prolongs the time element during which the offensive aggressive power is doing its work 

 of destroying the enemy. 



DEFENSIVE STRENGTH. 



Defense, or the attainment of safety, may be accomplished in three ways — by protec- 

 tion, by concealment, and by flight or evasion. 



A ship is defended by protection in two ways — namely, by armor in some form 

 against projectiles and other explosive attacks above water and by compartmentation 

 against invasion by water. The first form of protection is afforded directly to life, as well 

 as to the ship herself. The second form of protection is directly to the ship as a carrier but 

 only indirectly to the lives of those on board. 



It is in the battleship that we find the greatest development of protection. The 

 weight of armor is about 20 to 25 per cent of the displacement. Compartmentation is car- 

 ried to the highest practicable degree. But, as we have seen, combatant endurance is the 

 product of offensive strength and defensive strength. We must therefore get our full value 

 out of the battleship by making her strong in attack also. We do not know precisely what 

 relative weights of armament and protection will give the maximum yield, but the empiri- 

 cal solution which the best efforts of designers of all powers seem to have arrived at is that 

 the protective weights in battleships should be not far from twice that devoted to the arma- 

 ment and ammunition. 



For obtaining a defense by concealment we have two methods. One, the latest in 

 point of time, is the smoke screen, but the application of this method calls for no attention 

 in this paper. The second method of concealment is that of submergence, and its practice 

 requires a special type of vessel, the submarine, radically different from all others. In all 

 surface ships the design is such that it provides for a very large factor of safety by ample 

 reserve buoyancy. In all ordinary conditions the law of gravity is friendly to surface ships. 

 But in a submarine the combatant defense by concealment is gained only by the sacrifice of 

 navigational safety. In passing from the cruising to the diving condition, reserve buoyancy is 

 lost, and the law of gravity is turned from an attitude of benevolence to one of indifference 

 bordering on imf riendliness. The preservation of this neutral condition of no buoyancy be- 

 comes the chief preoccupation of all on board; it influences every movement and controls 

 efficiency in very great degree. Moreover, it tends, to some extent, to limit the size of 

 submarines. 



To make full use of the power of concealment inherent in her design, a submarine must 

 practice in peace and utilize in war what are known as "crash" dives, when the order to 

 close up openings is followed almost instantly by the dive. The life of the boat and 

 safety of all depend on every responsible man doing his whole duty with little time for the 

 captain to assure himself that his order has gone through and has been properly executed. 



As boats grow larger the difficulties of communication and opportunities for errors and 

 negligence by operators increase, and the law of "diminishing returns" so well known in 

 business comes into play. Difficulties in administration tend to become dangers in this 

 type and offset the advantages in design which are offered by increase in size of submarines. 



The submarine has not been a welcome development to all powers. It is the weapon of 

 the weak powers. To a navy, dominant, as is England's, a new invention can only threaten 

 its supremacy. England is therefore very slow to take up new things whose success would 



