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32. I troubled over a great deal. I have been working on this formula a long time, and several years ago I wrote that down the other way, and after thinking over it, I came to the con- 'clusion that wh cos. effect was greater water surface effect. That is shown by examination, and also by Fig. No. _ 6. For instance, in heeling a dock you ' cannot pump all the water out, you must leave some water in, and the amount of water left there, you take some point on the figure, that is some "distance from the center. Now, if there were no water at all in that compartment, certainly. the capsizing moment in the other direction would be eae because there is no weight there, -- _ Deriving the formula - with Sigma i it has been proved in naval architecture that the loss due to Sig- Ma i is independent of the weight of the water. It involves that point. ~The only proof is this--that water changes its shape, but it acts always through its center of gravity. Going back to first principles, the weight goes through its center of gravity, and therefore if this water is in the compartment, it gives the moment due to the resistance from the side, and if it were not there at all, why the -moment 'n the other direction would be greater. It involves that point. As to the side walls being built for strength, Prof. Peabody makes mat Statement in his treatise on naval architecture, and it is correct to assume that, because it makes a Greater factor of safety. If the side walls are longer, made of sufficient 'strength to provide the necessary pro- tection, there would be an additional factor O1 safety. I have treated it as a single beam fixed together, and a connection between the side walls and center pontoons re. all brought into stress and treated ex- actly as if they were one single beam interconnected throughout, because they are interconnected, and because these disconnections here are weaken- 'ing points, as shown in the particular Case Of this breaking. That is to say, it is weaker by these discon- 'nections than it would be without them, so, therefore, by making this continuous, these bolts -outside help to strengthen the dock through this section, and a strong dock is the re- sult.' Now, replying to Mr. Donnelly. he speaks of taking care of strains and Stresses due to. shifting ballast by . means of pumping. Of course, that is done. If a ship has a drag, of course you regulate that, not by stopping certain valves in pumping, but you regulate it in only one way in prac- other The Marine REVIEW tice that I know of--and I have had practice in that connection--and where you are pumping you cannot do it when you are pumping up. You can only do it when you are flooding, and the only way to do it when you are flooding on an even keel, when you ' wish to give a lift to this side, you- do it by stopping the valves here, and that shuts off one of the com- partments, and the water brings the compartments throughout at the same level. We cannot shift bal- last in the government docks: to the same extent they do in commercial practice. As to the features ean out about neglecting transferred stability by ~ making 'provision that this' compart- ment. shall be watertight, it is per- fectly safe, because when he studies over the thing further, he will. see that the factor Sigma.1. that. comes in the formula, due to the subdivisions as shown in this data, are so simple that they can be accepted ent'rely, and they are such as to compensate for transferred stability. In -these lines, these other lines of center side, keel blocks are_in- serted to support these blocks, and take the weight of the ship at the points where it is needed, to assist in the general strengthening of the dock, and not compensate for the transferred stability, because they are more than necessary to do that. The bulkhead should be watertight in commercial practice, yet in gov- ernment practice these bulkheads have holes, and these are watertight. This is immateral, because there is plenty of stability anyhow. In docks of this character there is not much control possible by varying the pumping, ex- Gept in the forg and ait trim, ande that by closing one valve and leaving the other valve open, because all wa- ter which is in the pontoons is inter- connected in the pontoons and assume a practically level form. In the discussion of Civil Engineer Cox, Mr. Cox has'had perhaps more to do with these docks than many oth- ers here--while he has -had a great deal to do with the actual details of the _Dewey, and this dock--referring to his discussion, he touches upon the towing line, and he says that he would depend more upon a long tow. line--that is, he would take more care about that than avoiding square ends to a dock, which is to be towed a lone distance. I differ from him fon .that point very materially, and base my judgment entirely on the tes- timony of the seagoing officer who handled the Dewey dock when she went to Manila, discussion He discusses the question of the fa- cility with which the New Orleans dock was towed to New Orleans, it having square ends. It is true that has had square ends, but the builders, partly for the purpose of that tow- ing, built on a round nose to the dock of wood, and it had the effect of having a round nose temporarily. There is another point in Mr. Cox's in which he says it is very interesting to be able to deter- mine the internal water surfaces over the draught, etc., but it' has no par- ticular saving. Of course, we could not get along without a knowledge of that. What he means is this--when the dock is submerged to its greatest submergence, the internal water head comes to about. that level. If the -dock is entirely submerged, more than that, it never gets higher than that on the inside. Now, the water spaces of the dock include up to that level, so that that space is never used for water ballast, although it is built and liable for that purpose. This space above is used for docking machinery, sbore. rooms of the dock, one on either side, and similar purposes. What he means is this--suppose here, knowing the interior water level, and knowing, therefore, you do not need this for docking purposes, he means fiat space 15 not necessary to use for any other purpose, and I will agree in that dock I cannot see any great use for it, because the -com- partments here are more than ample to take-care of the machinery, and also all the stores which it may be desired to put in the dock, and per- haps not more than 25 per cent of this space is used, and not that much for these, purposes after the dock is at its naval station. If it is on a voyage, that is different. Besides having a value the knowl- edge of this level is important. Of course, in here (indicating) you do not need this for machinery, unless you want to put in a machine shop, etc, and. it might be desirable to put horizontal bars. at this level, so when the dock is filled with water completely it would stop here, and remain stable, have reserved stability, even though an accident should hap- pen to the flow and prevent the dock from sinking, in case there was an accident. As a matter of fact, the pumps on this dock will keep going day and night, and the amount of cost of having a man on hand in case of an acci- dent, or a valve failing, is a great expense, whereas, if the dock was so arranged that in case of a valve giving way, or a small leaking should ae a lS Ns a