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August, 1917 rocker is ‘very . flat, resulting ina greater distance of the center of gravity below the center of curva- ture, the chair will be stiff and harder to rock or heel from the upright po- sition. The metacenter of a ship cor- responds very closely with the center of curvature of the rocker, as already described. After Bouguer developed the con- ception and mathematical methods for calculating the position of the metacenter, Atwood carried the mat- ter further by calculating the righting arm or lever, which, multiplied by the weight involved, measures the torque when a_ vessel is_ inclined. The metacentric conception applies only to initial stability with the vessel upright, and for many years appears to have been sufficient, particularly as applied to. sailing ships, which were very much of the same general type, with comparatively -small vari- ations of general form, relative free- board, etc. An Experiment That Capsized Something more than 50 years ago, however, the loss of the CAPTAIN brought home very strongly to naval architects, particularly in England, the fact that there was another factor involved in stability. A distinguished English officer, Capt. Cowper Coles, took up with enthusiasm the monitor idea, first developed by Ericsson in this country, and as a result of his campaign there was built in England a low freeboard vessel called the CapTaIn with turrets and also full sail power. Naval architects of the English admiralty were not enthusi- astic over the type. The vessel had much less metacentric height than the pure monitor type, but early re- ports and experience with her indi- cated that she would be a_ great success, until on the night of Sept. 7, 1870, in the Bay of Biscay, with a moderate gale blowing, she capsized, with a loss of 481 lives, including Captain Coles himself. The vessel was perfectly safe until conditions were such that she_ heeled - over enough to bring her deck edge well under water. After that her righting force rapidly decreased, and at a comparatively small heel became neg- ative, resulting in capsizing. Under the weather conditions existing the force of the wind against the, sails of the CapraIN was sufficient to heel her beyond the safety angle, and over she went. The investigation into this disas- trous occurrence brought out the fact that a vessel with a comparative- ly small metacentric height may be perfectly safe if it retains a righting THE MARINE REVIEW tendency at a large angle of inclina- tion—a feature associated primarily with high freeboard. On the other hand, a low freeboard vessel, with a comparatively short range of sta- bility, may also be perfectly safe if. its metacentric height and initial sta- bility; are very great, so far that a large amount of work has to be done to incline the vessel throughout its comparatively short range of stability. ‘Work at Model Basin “Admiral Taylor’s career of con- structive work began as a member of the corps of naval constructors of our navy, in which position he greatly distinguished himself by solving a number of important prob- lems in connection with the resist- ance and power of ships. The re- sults of this work are recorded in numerous papers which he present- ed before the leading engineeriny societies of the world, and in two comprehensive treatises. His books on the ‘Resistance of Ships and Screw Propulsion’ and on ‘The Speed and Power of Ships’ have come to be universally recognised as the standard works upon these subjects. “But his most important contribu- tions to the scientific side of naval architecture are based upon the work he conducted at the United States experimental model basin, which he designed and constructed at Washington, in 1897, and of which he had charge until 1914. During this period of his life a surprisingly mide range of subjects engaged his attention, and many instances might be cited in illustration of his re- sourcefulness in formulating and experimentally attacking problems in subjects of which. very little was known before. A case in point is his brilliant experimental researches on ‘The Interaction Due to Suction Between Passing Vessels, a sub- ject on which there was little or no reliable information, save a few observations on cases of damage to ships by unexplained collisions. By his brilliantly conceived and suc- cessfully conducted experiments he placed the subject on a_ scientific basis.’—From the presentation ad- dress. This whole question is now fairly well understood, and the naval archi- tect is enable to adjust his metacen- tric height as he will by varying pro- portions and dimensions of the ship to suit the position of the center of gravity and type of vessel—all re- quiring very careful and detailed cal- culations. As a matter. of fact, there are passenger vessels crossing the Atlantic in perfect safety with no initial stability, or even slightly nega- tive metacentric height, their free- board and shape giving them a range of stability of as much as 90 degrees. Since the days of Fulton’s first steamboat the design of vessels’ hulls, pag on such lines as to give the minimum resistance in passage through the water at varying speeds, consistent with the other characteristics of the ship, has become increasingly impor- tant. This is well illustrated in the case of the new battle cruisers, to which I have already referred. To arrive at the most advantageous di- mensions and form of hull, for pur- poses of the high speed desired, there were made and tested in the model tank at Washington upward of 20 models, with the result that the re- sistance of the model finally adopted was nearly 15 per cent less than that of the first model tried. _I would particularly invite attention to the fact, however, that this was by no means due to improvement in shape of lines alone, but also to other changes which were adopted with some reluctance, but which it was known in advance would materially reduce the resistance. Experience in recent years has fully. confirmed the © con- clusion drawn from model basin in- vestigations that, for high-speed ves- sels, the length is a primary factor. In’ fact, we know in the majority of cases of high speed vessels that we could reduce resistance by increasing the length. This usually involves, ‘however, increased weight of — hull and other objections. So that for large, fast vessels the naval archi- tect usually adopts dimensions which do not give the minimum resistance for the displacement, but the best all- around result, considering the total weight, including both hull and ma- chinery. Why Battleships Are Short Men-of-war in particular are gen- erally made relatively shorter than merchant vessels, for the reason that ordinarily they travel at a low speed, and the long vessel requires more power at low speed than the short vessel, and hence on a given endur- ance requires a greater weight of fuel. The merchant’ vessel, particularly the fast passenger vessel making its passages at top speed or thereabouts, must be economical at that speed. A hundred years ago the ideas of ship resistance were entirely crude, the usual opinion being that the re- sistance was in proportion to the area of the cross section of the ves- sel which had to be forced through the water. About the middle of the last century Rankine put forward a theory which went to the opposite extreme. His proposition was that in a well formed vessel the resistance was entirely due to the friction of the surface against the water, and he developed a method of estimating this.. Our modern ideas on this sub-