Slow Match. Port Fires.-Bickford's Fuse.-Signal Rockets. - Congreve Rockets. Carcases. -Tube. -Gun Cotton.- Field-piece Carriages.-Ele- vation and Plan of Brass Field Carriage.-Weights and Dimensions of Small Arms in use. Shot. Getting in Guns. Rigging Yard Purchase p. 245 Material and Value of Boats.- Weight and Tonnage. - Coppering. - Hoist- - - - - 263 Parts of Sails. - Weight and Price of Canvass used. Strengtheners. Eylet Holes, Clues, and foot Ropes. Cutting.-Size and Proportion of Sails for different sized Boats. Different Modes of Pointing Sails. - Table of Yards and Size of Canvass required for certain Sails for Ships of different Rates.-Table showing Purposes for which the Classes are suitable.-Table of Weight of Sails. Table of Time required to complete certain Sails of certain Dimensions. - Table of a Man's daily Work, and of Length, Num- ber, and Weight of Points in Sails of different Class Ships.- Sail Tackle.— Bending Sails, Top Sails. Courses. - Spanker Head Sails.-Top- gallant Sails and Royals.-Boom Mainsails.- - Trysails. Studding-Sails.- Area and Centre of Effort, Axis of Rotation.- Natural and direct Resist- Advantage of flat and Disad- Measures of Time. The Pendulum. Compensation Balance. Table of length of Pendulum vibrating Seconds in different Latitudes. Tables of Weights and Measures.-Table of Miscellaneous Weights and Measures. Relative Value of British and French Weights and Measures. — Table of relative Value of British and Foreign Measures of Length. Table of relative Value of Commercial Weights. Lead Lines. Log Lines. - CHAP. XXI. PREPARING FOR SEA. - The Compass.- Mode of adjusting Compass. — Variations of the Needle.- CHAP. XXII. HANDLING BOATS. p. 335 Capacity of Boat. Taking in Stores. Precautions before shoving off. CHAP. XXIII. ANCHORING. - 343 Anchoring on Signals.Mooring. - Position of the Anchors, and Direction of CHAP. XXIV. HANDLING THE SHIP. - - - 355 Experience, Promptitude, and Invention, necessary for Command.-Casting.- - - - 381 - Expansive Gear. Condenser. Hot Well.- Dead acting oscillating Engine.-Trunk Cylinder Engine. Throttle Valve. - Indicator. Rule for calculating the Distance travelled by Piston in a given Time. Weight and Cost of Engines. The Screw. - Handling the Propeller. Distilling apparatus.- Action of Parts of Engine in Dis- A MANUAL FOR NAVAL CADETS. CHAPTER I WATER AND AIR. THE Theory of naval architecture is founded on those branches of the science of watery fluids which are comprehended in the term Hydrodynamics. Those are -Hydrostatics, which treat of their pressure when at rest; Hydraulics, which treat of them in motion; and Pneumatics, which treat of the pressure and motion of air and other elastic fluids. The Questions then arise, what is water? and what is air? Every substance which comes under the cognisance of our senses is called matter, and is made up of atoms, each of which, however minute, has length, breadth, and thickness, and occupies a space into which another cannot enter until the first has been displaced. If, for example, we immerse a solid in a vessel full of water, a portion will overflow equal in bulk to that of the body which is submerged. This property of matter is called its Impenetrability. In some bodies the atoms are closer together than in others, and, although of similar volume, would have greater gravity. This is the Density of matter.* The quantity of space which *The earth is a mass of matter, about 5 times heavier than an equal volume of water; or, what is the same, the mean density of the earth is 53. The total weight of the earth is more than 6,000,000,000 billions of tons. B a body occupies, is called its Volume or Bulk. All bodies on or near the earth possess gravity (or weight), and tend towards the earth's centre with a force called centripetal, proportionate to their respective densities. Fluids press equally in all directions, upwards, downwards, obliquely, or laterally. Solids press only downwards. The pressure of a fluid on a lighter body, or a rarer fluid, arises from the heavier fluid seeking to maintain its own level, or the level of its own weight. The extraneous body is therefore driven upwards, as in the case of gases, steam, vapour, smoke, &c. Most substances are made up of two or more others, so intimately associated, either by mechanical mixture or by chemical combination, as not to be separable, except by extraordinary means. The component parts are held together by an attractive force called "Cohesion," which is greater in solids than in fluids, and altogether absent in gases. When solids are exposed to a certain degree of heat, they change their state: some are converted into liquids; liquids into vapours; and again, by a like loss of heat, these revert to the liquid state; and liquids, by due degrees of cold, are solidified. In others, the conversion is into smoke. This property of matter is called its "extension." In some cases these substances may be taken to pieces, and each part further investigated a property of matter which is called its Divisibility; but when they resist all separation, they are called simple or elementary. Those substances which it most concerns us to consider in reference to the question we are investigating, are oxygen, nitrogen, and hydrogen. Oxygen is only known as gas. It is a little heavier than atmospheric air, and 740 times lighter than water. It is the principle of combustion or burning, and indispensable to the support of animal or vegetable life. All substances which are capable of combustion in common air, burn with far greater intensity in an atmosphere of pure oxygen; but were it inhaled by animals in this form, they would expire from excess of vital action. Nitrogen, or azote, has neither colour, taste, nor odour. It extinguishes flame, cannot support life, and counteracts the activity of oxygen in that mechanical mixture of these two gases which compose our atmospheric air. |