In the descriptive parts of the work we have been governed by the same considerations. The application of the force of steam to mechanical purposes has been proposed on various occasions, in various countries, and under a great variety of forms. The list of British patents alone would furnish an author of common industry and application with matter to swell his book to many times the bulk of this volume. By far the greater number of these projects have, however, proved abortive. Descriptions of such unsuccessful, though frequently ingenious machines, we have thought it adviseable to exclude from our pages, as not possessing sufficient interest for the readers to whose use this volume is dedicated. We have therefore strictly confined our descriptions either to those Steam Engines which have come into general use, or to those which form an important link in the chain of invention. _December 26, 1827._ CONTENTS. CHAPTER I. PRELIMINARY MATTER. Motion the Agent in Manufactures. -- Animal Power. -- Power depending on physical Phenomena. -- Purpose of a Machine. -- Prime Mover. -- Mechanical qualities of the Atmosphere. -- Its Weight. -- The Barometer. -- Fluid Pressure. -- Pressure of rarefied Air. -- Elasticity of Air. -- Bellows. -- Effects of Heat. -- Thermometer. -- Method of making one. -- Freezing and Boiling Points. -- Degrees. -- Dilatation of bodies. -- Liquefaction and Solidification. -- Vaporisation and Condensation. -- Latent Heat of Steam. -- Expansion of Water in Evaporating. -- Effects of Repulsion and Cohesion. -- Effect of Pressure upon Boiling Point. -- Formation of a Vacuum by Condensation. Page 17 CHAPTER II. FIRST STEPS IN THE INVENTION. Futility of early Claims. -- Watt the real Inventor. -- Hero of Alexandria. -- Blasco Garay. -- Solomon De Caus. -- Giovanni Branca. -- Marquis of Worcester. -- Sir Samuel Morland. -- Denis Papin. -- Thomas Savery. 38 CHAPTER III. ENGINES OF SAVERY AND NEWCOMEN. Savery's Engine. -- Boilers and their Appendages. -- Working Apparatus. -- Mode of Operation. -- Defects of the Engine. -- Newcomen and Cawley. -- Atmospheric Engine. -- Accidental discovery of Condensation by Jet. -- Potter's discovery of the Method of working the Valves. 51 CHAPTER IV. ENGINE OF JAMES WATT. Advantages of the Atmospheric Engine over that of Captain Savery. -- It contained no new Principle. -- Papin's Engine. -- James Watt. -- Particulars of his Life. -- His first conceptions of the Means of economising Heat. -- Principle of his projected Improvements. 69 CHAPTER V. WATT'S SINGLE-ACTING STEAM ENGINE.