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318 case when making applictaion for first inspection to carry passengers, shall be subjected to an _ inclining test conducted under the supervision of the supervising inspector general, and the results of the test shall be approved before the vessel shall be certificated. The owner or builder of every ves- sel described in the second paragraph of this section shall, as soon as possible, furnish the local inspectors of the district where the vessel is to be inspected drawings or blue prints, as_ follows: Sheer, half breadth and body plans, midship sec- tion, inboard profile, floors, framing, bulkheads, arrangement of decks and quarters; general arrangement and location of boilers and machinery, plan and elevation; plan and eleva- tion sections through holds, tanks, bunkers, double bottoms, and compart- ments; capacity plan of the bunkers, tanks, holds, double bottoms, and com- partments; and the following curves: Displacement, vertical center of bouy- ancy, transverse metacenter. longi- tudinal center of buoyancy, transverse metacenter, conter of gravity of wa- ter planes from either perpendicular, moment to alter trim, and tons per inch; except for double end ferry boats, then the drawing or blue print of curves will only be required to show the displacement, vertical cen- ter of buoyancy, transverse metacen- ter, and tons per inch. The drawings and blue prints required bv this para- graph shall be forwarded, upon re- ceipt of same, by the local inspectors to the supervising inspector general. Where vessels are required to carry fixed ballast, in order to increase the metracentric height, such ballast shall not be moved except for examination and repair of vessel, and then only in the presence of an inspector of this service. (Sec. 4405, R. S.).” It will be observed that the stability tests of this service are conducted under the supervision of the super- vising inspector general, and_ this work is at present being done by Capt. Chester W. Willett, one of the traveling inspectors, who has _ his headquarters in the office of the sup- ervising inspector general, in Wash- ington, D. C. Captain Willett is an officer of extensive experience, and formerly had his headquarters’ in Cleveland. While considerable study is required in perfecting the details of a practicable and efficient method for conducting stability tests, there is nothing mystifying about the cal- culations for stability. They are merely a mathematical application of the laws of gravitation, and a little necessary yawing before proceeding with the measurement. ‘ An Inclining Experiment Is Made Upon conducting an inclining ex- periment, the ship is first put in condi- tion, plumb bobs are suspended from convenient places and arranged in such manner that accurate records of MARINE REVIEW the lines may be made, and their de- flections measured on a batten. The weights of the inclining ballast are carefully made and recorded and the distance of the movement of the weights accurately determined. As- signed positions are taken by all men on board, the draft marks are read, and zero readings made on the batten. The weights are then moved, and various checks made of the in- clination of the vessel, and aside from numerous details the work is com- plete, ready for a continuation of the calculations which have began with the offsets and displacement sheet of the vessel. The position of the center of gravity is now found by subtracting from the height of the metacenter the result obtained by multiplying the cotangent of the an- gle of inclination by the moment of DIAGRAM ILLUSTRATING AN INCLINING EXPERIMENT TO DETERMINE CENTER OF GRAVITY the inclining weights divided by the weight of the ship. Weights and pas- sengers are now moved on and off the vessel, in algebraic sums only, and various conditions are worked out on forms and the measure of the stability is thus actually determined. Stability of a ship in its finality is a somewhat cumplicated subject, and, in all its phases runs the gamut from the simple to the complex. Many factors enter into the final calculations which can only be properly treated in a text book on the subject. Ships vary to a great extent and to de- termine the value of stability each type must be sliced and cored, and, in the mathematical analysis of the complexities, the measure is found. Ships may vary, but figures are constant, and facts agree. The meas- ure of the weight of volume of water displaced by a vessel at any draft is the total weight of the ship. For convenience the word volume is used. Volume here implies bulk. The basic principle of the stability of a vessel is the location of the center of gravity of its volume. From these two laws, discovered by Archimedes and Newton, September, 1925 respectively, are deduced all the prin- ciples and laws governing a ship’s stability. From the laws of gravi- tation, the center of gravity of a fixed body is the center point of its vol- ume, and without calculation it is known that the center of gravity of a homogeneous circular plate is the center point at which the plate will balance, or the center point of the circle. The hull of a ship and weights on board are composed of unevenly dis- tributed materials, and each separate mass of material, regardless of size or location, has a center of gravity point, but as the force of cohesion is greater than gravitation in the unit, the resultant sum of the infinite number of forces of gravity of the connected masses which is called the ship, act in unison. In order for a designer to determine the location of the center of the vessel, he must cal- culate the exact weight and location of everything that enters into the construction and equipment of the ves- sel. It therefore becomes impracti- cable, if not impossible, for an archi- tect to determine accurately the center of gravity of a vessel by any other means than by an inclining experi- ment. The purpose, therefore, of the inclining test is to determine the position of the center of gravity of the vessel, from which the measure of the initial stability is made, as well as other calculations to deter- mine the statical stability, range, and vanishing point of stability, with a view to assuring a stable ship as a measure of public protection. Location of C. G. All Important As the body of a ship is symmetri- cal of both sides of the fore and aft center line, the center of gravity must be at some point in the fore and aft center vertical plane, and is constant only for a fixed condition. A body suspended in the air is acted upon by gravity alone, and the location of the center point of the weight rela- tive to the supporting point deter- mines whether the body will remain upright or upset. The same body when afloat in calm water is acted upon by gravity in the same manner, but now receives that upward sup- port of the surrounding water, which we called pressure, or buoyancy. These opposing forces, each of the same amount upward and downward, are influenced in their action by the position of the center points of their volume. When the body is at rest or in equilibrium these two forces act along one line, that is, the center of volume of the displaced water is on a