TABLE OF CONTENTS. Indicators of Saltness of Water in Boilers Process of Blowing-out; Brine Pumps Dimensions of Cylinder and Power of Engine Reports of the "Volcano" Steam Vessel Report of the "British Queen" Steam Vessel Howard's Method of generating Steam Field's Cycloidal, or Split Paddle Wheel Buchanan's Wheel; Morgan's Wheel Loss of Power by deep Immersion of Paddles Mr. S. Hall's Patent Reefing Paddle Wheel Engines of the "Ruby" Steam Packet Dimension and Speed of the Engines References to the Frontispiece Application of the Steam Engines of the "Gorgon" Steam Frigate Effects of Water on Clay Cuttings Treatment of the Surface of Slopes Illustration of the above Principles CHAPTER I. PRELIMINARY OBSERVATIONS ON HEAT AND STEAM. 1. General Effects of Heat upon Bodies.-One of the most general and obvious effects of Heat, is expansion: all bodies when heated expand, or increase in bulk, and on cooling they contract, or return to their original dimensions. Solid bodies expand much less than those which are liquid or gaseous, and are consequently not employed as a moving power for the purpose of transport. Liquid bodies present several phenomena on the application of heat, of sufficient importance to qualify them for locomotive purposes; the expansion of water, for instance, is forty-five times greater than that of iron. Gaseous bodies expand much more by heat than liquids, their particles being in less intimate union, and less under the influence of cohesive attraction; the expansion of air, for instance, is eight times greater than that of water. Bodies which undergo expansion by heat, undergo also an increase of temperature; and as these two effects are always simultaneous, the one has been adopted as a measure of the other. Upon this principle is constructed the common thermometer, which is merely an instrument for measuring degrees of temperature by their effect in the expansion of some liquid body. It consists of a glass tube with a bore of very small and regular calibre, having a bulb blown on its extremity; the bulb and part of the tube are filled with mercury, this metal being the most uniform in its expansion at all temperatures. By boiling the mercury, the air is expelled from the rest of the tube, the extremity of which is then hermetically sealed. A scale marked with degrees is attached to the tube, and the variations of tem B 2 GENERAL EFFECTS OF HEAT. perature are indicated by the expansion or ascent, by the SOURCES OF STEAM POWER. 3 in an arrangement of the scale, in which the freezing point is marked 0, or zero, and the boiling point 100°. In Reaumur's thermometer, which is employed in the north of Germany, the freezing point is marked 0, or zero, and the boiling point 80°. The degrees are continued of the same size below and above these points, those below being reckoned negative. A figure is added in the preceding page, showing the correspondence of the three thermometers with each other. These different modes of graduation are easily convertible: the Centigrade scale is easily reduced to that of Fahrenheit by multiplying by 9, and dividing by 5; that of Reaumur to that of Fahrenheit by dividing by 4 instead of 5; or that of Fahrenheit to either of the others, by reversing the process. Thus: Cent. 100° x 9900 ÷ 5 = 180 +32=212o Fahr. Or, by reversing the order: Fahr. 212°-32 = 180 × 59009 Fahr. 212o - 32 = 180 × 47209 = = 100° Cent. * 80° Reaum. 2. Sources of Steam Power.-The natural phenomena by which the Steam Engine becomes a moving power, are few and simple. They consist in the mechanical forces produced:-1, by the expansion of water into steam; 2, by the elastic force of the steam thus formed, and 3, by the reconversion of steam into water. Water is capable of existing in the solid state as ice, in the liquid state as water, and in the vaporous state as steam. These changes of state depend upon varieties of temperature and atmospheric pressure; and they are connected with certain phenomena which must be generally explained, before their application to the Steam Engine can be understood. They may be studied in the following order: This, and several other paragraphs of the present chapter, are taken from the first chapter of the Author's Manual of Chemistry, to which the reader is referred for further information on the nature of Heat. |