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26 in connection with this discussion it might be interesting to mention it again. Mk | P. H. Kemble: On page 20, at the top of the page, Mr. Chace makes this statement: "The consumption of the main engine may be taken as one pint per horsepower hour at full power and five-eighths pint per horse- power hour at half power." I under- stand that to mean when the engine is running at reduced power it is more economical than when running at full power, which seems rather an unusual condition for internal ex- plosive engines. -- D. W. Taylor: It seems to me that Mr. Chace in this paper has touched upon what"is really the most. vital point in the development of subma- rines. For several years on various occasions I have askcd the managers of our battleships what they would do if they had their ship in the vicinity of submarine work, and that is one question upon which our naval offi- cers are in absolute agreement. They all said they would probably get away. So far, the submarine has never been given sufficient speed to enable it to catch a pbattleship. It looks to me, if we had a submarine which could catch a battleship, that question as to what they would do in the event of a submarine being in the vicinity would be a difficult one to answer. The fact is the battleship has not devel- oped any antidote for the submarine. The defensive powers of the submarine are practically unlimited, because it can go under water, and we have no weapon, so far, capable of attacking it under water, so that the question of the possibility of the increase of speed of the submarine is very important. Mr. Chace takes no very strong ground one way or the other, but I rather think he believes the true plan _ of development is to produce the surface speed and hold to the sub- merged speed, the submerged speed being secured by the storage battery, and the surface speed being obtained by the gasoline engine. With reference to Mr. Chace's re- marks on page 10 as to the question of the depth of submergence, it seems to me that the qeustion of submer- gence, with or without the crew, has very little bearing. If the boat is sub- merged a certain depth without the crew, it seems there is no reason why it should not be submerged with the crew, it is simply a question of what is best to do. I will point out with regard to the depth of submergence that the United States is peculiarly situated in this connection, because it Tae Marine. REVIEW 4 has a very long coast south of Boston, where the water is very shallow, and there are very few spots, indeed, south of Boston where you can ob- tain 200 feet of waten without going a long way outside of the line, and for that reason the advantages of sub- marines, which can withstand a deep submergence test, are greater for the United States than most other na- tions, where you may find depths of 400 or 500 ft. within a very short dis- tance from land. ' I was very much interested in the deductions as to the possibility of speed. I ask him, with reference to page 13, if submarines of less than 100 tons made over 12 knots speed. task him, if he is at liberty to an- swer the question, whether' those boats were as much as 100 ft. long? y Mr Chace: = Ishduld not care. 'to give the dimensions, they were not the same as the impulse test in the model tank in Washington; they were modified before the boats were built. Mr. Taylor: The reason I ask the question is because we have made a number of experiments with models of submarines, which appeared to in- dicate that there is a certain critical speed, beyond which the model has a strong tendency to dive. We remem- ber the case of the English subma- rine a few years ago which was par- ticipating in some maneuvers' and took a header and went down and drowned nearly all the crew, and even before that we made a number of models and found apparently there is .a critical speed at which such things happen. We have done it on models, and as the speed increases they take a header and go down. That speed is tolerably high, and personally I should be much averse to going on submarines, unless it had a very large emerging displacement, whicn had suf- ficient power to drive it at a speed greater than one and one-quarter or one and three-tenths times the square of the length. If you will look at the diagrams in plate 1, you will see that that speed goes beyond the hollow in the curve, that fs to say, all of these vessels would be safe for a compara- tively small reserve of buoyancy up to some point at which the power be- gins to rise very rapidly, beyond a hollow in the curve, that is with a 100-ft. boat up to a speed of 13 knots. It was that fact that made me in- terested in knowing the length of the 'boat that made 12 knots, it was prob- ably not a large boat, not over 100 ft. Mr. Chace: In regard to the ques-. tion of mine charges that Capt. Hov- gaard brought up, I can state that I " paper, 'have seen actually under construction mines which were designed to be used as freely floating mines which had that charge of 500 pounds, so there can be no question but what charges of mines actually used reach that amount, or exceed it. As to the possibility of placing the long diameter of the oval ,section horizontally as suggested by Capt. Hovgaard, I remember reading his article on that subject to which he refers. If we reach ovals of very large displacement, possibly there will be a development along these lines, especially in so far as the aft body is concerned, where it may be an advantage to use the oval sections with the long diameter of the oval | horizonal, particularly if triple screws are used as suggested. Now, as regards the question of consumption, that is an error, I should have said five-eighths of the full power consumption at half power. These notes were dictated, and not revised, and in this way the error crept in. The half power consumption is five- eighths of the whole power consump- tion; that _is the fact which holds. The figures and comments which are given as to radius are in no way af- fected by this typographical error. As far as the question of increasing the surface speed and maintaining the same surface speed, that is really the thing I had in mind in writing the to draw attention to the fact that a higher surface speed is abso- lutely necesary if we are to place the submarine where it can fight ef- fectively against large ships, making the speed which these large ships do make; higher submerged speed than these actually obtained do not seem to be necessary, but great importance should be attached to increasing the surface speed; this is particularly im- portant in the case of off-shore works against large ships. In regard to Mr. Taylor's remarks, -- when models. of . submarines are towed at speeds far above those for which they are suited they may be- - come erratic in their movements. Un- der such conditions wave-making would become abnormal, and if longi- tudinal stability is lacking the model may show a tendency to go down by the head or to dive. I believe that many cases where existing subma- rines, when running on the _ surface, have shown a tendency to change trim suddenly can be explained by the presence of loose water in partially filled ballast tanks. The great danger of running under such conditions must be empha-