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30 a. Safety. 2. Facility and certainty of action when submerged. 3. Speed when running on the sur- face. 4. Speed when submerged. 5. Endurance, both submerged and. on the surface, 6. Offensive power. 7. Stability. 8. Visibility of object . to be. at. : tacked. Had the navies of the world fol- lowed this order of valuation of de- sired elements in the designs of their submarines, the lives of 60 odd per- sons need not have been sacrificed, as they have been during the past three years, by disasters to submarines. In making any comparative table it is not possible to secure a true esti- mate of the relative merits without considering the elements above named; and should any change be made in that scale of values, no change of position could excusably alter the prime and vital importance of safety. I am willing to concede that, per- haps, the cigar-shaped form of vessel is capable of greater speed when run- ning submerged than is possible with other forms upon a fixed measure of displacement and power, but I con- tend, without fear of authoritative contradiction, that experience with the diving type of vessel, during the past 100 years, has shown that it is too unstable and unreliable to be safe. According to numerous official re-: ports both in this country and abroad, it has been shown that this cigar- shaped form of hull, common to the diving type, has a tendency to cause .the boat to make sudden and unex- pected head-first dives. In these re- ports it is shown that it is necessary for the crew to remain at their sta- tions and that a very delicate adjust- ment of ballast, and men of long train- ing and quick juggling skill, are re- quired to navigate and) to control these boats when running submerged. I shall not take your time to read extracts from the numerous reports made upon this line. Sir William White, Prof. J. H. Biles, Rear Ad- -miral Melville, Rear Admiral O'Neil, Capt. Edgar Lees, and Captain Bacon have amply testified in the various discussions and hearings upon the sub- ject of the submarine, and the acci- dents that have happened to that class of vessel. Mr. Spear has implied by his dis-. cussion of the question of stability that a boat with a water-tight super- structure has less stability than one without a superstructure; and for the purpose of making his point he has ~ actually decreased. TAE MarRINE. REVIEW taken the Protector as a type and has assumed conditions which do not ex- ist an modern boats of' the "Lake" type, fitted with superstructures. He will, perhaps, be surprised to learn that in some of the "Lake" boats now under construction the center of buoy- ancy is as much as 22 in. above the center of gravity when in a submerged condition. ' I doubt if any of the diving boats in | Even the: existence have half of this. Protector, referred to. by Mr. Spear, 'must have had greater stability than the Fulton, according to the official reports of the operations of these rival ° boats. _ There is an old saying that "the proof of the pudding is in the eating." In the official trials of the Protector, in Russian waters, there were 19 per- sons on board, including the officers of the commission and a Russian trial crew undergoing instructions and her own. crew. These men were permitted to move freely about in the boat. In the later boats several men have moved at one time from the extreme forward end ot the' boat. to the extreme after end of the vessel--while 'running submerged--without changing the depth of submergence more than - a few inches. In discussing stability, Wr Spear says: "By fitting watertight superstructures the ac- tual center of buoyancy may be raised but the metacentric height, far from being increased, is This arises from the fact that such superstructures cannot be constructed sufficiently strong to withstand high pressures, hence must be filled with water when sub- merged. It follows inevitably that the center of gravity is raised as much as the center of buoyancy, leaving the stability intact, but the large weight represented by the large super- structure raises the center of gravity of the hull as a whole and so diminishes the metacentric height."' The first mistake is in the assump- tion that by admitting water into the superstructure the center of gravity is raised. He has lost sight of the fact that, when submerging, water is also admitted into the lower ballast tanks, and that if more water is ad- mitted into the lower tanks be- low the normal center of buoyancy than is' admitted: in «the. superstructure above .the center of buoyancy, the center of gravity in a submerged con- dition may also be lowered. The next wrong assumption is that the air and fuel tanks used for stor- age purposes "generally weigh more than the water they displace and so serve to further decrease the metacen- tric, height.' As a matter of fact, the fuel tanks, astsed "in the "Lake? boats, even when filled with gasoline, weigh less than the water they displace, and con- sequently add a buoyant moment well above the center of gravity of the dition. - boat when she is in a submerged con- dition. In the lest 'type of the "Lake" boats the cigar-shaped form' of hull has been abandoned, thereby raising the center of buoyancy of the main hull six inches above the center of buoyancy of a corresponding hull of cigar-shaped form. The superstructure itself, even when filled with water, adds a large buoyant moment several feet above the center of gravity. This' is owing to the buoyant character of its construction. As a result it is pos- sible to secure a form giving a differ- erence of 22 in. between the center of buoyancy and the center of gravity, when the boat is in a submerged con- I do not believe that it is possible to distribute the machinery in a hull of cigar-shaped form so as to get a difference at best of more than 10 in. between the center of buoyancy and the center of gravity of such a vessel submerged. I would like to call the attention of the members to the sketches which I have made on the blackboard showing the difference between the stability ca- pable of being attained with the cigar- shaped form of hull, as used in the diving type boats and the form of hull used in the submersible type, herein referred to, with buoyant superstruc- -ture and hull of different form. There is sufficient testimony to the point that the diving submarine must be run at a considerable speed in or- der to get her under water, unless her © reserve of buoyancy is very small and her longitudinal stability slight. The greater the stability of the diving boat, the hizher must be her speed in order to enable the vessel to make her initial plunge. Model experiment- al tank trials and the fatal records of the past three years have shown that 'there ate certain forces exerted at the bow of a spindle-form diving boat which exert a down pull at higher speeds and tend to make the boat plunge when least expected. The British may be said, I think without fear of contradiction, to have brought the diving type to its highest state of perfection. But notwithstand- ing this, the numerous fatal disasters and narrow escapes from serious mis- haps among their submarines, have caused them--as I was recently in- formed by a British officer in an au- thoritative position--to abandon the exclusive use of the stern rudder and, to quote this officer, "to adopt the hy- droplane as -heir means of sugmerg- ence." According to a recent article by Sir William White. (see page 948 of the