The section of this work which treats of the causes and the extent of losses of heat in the steam-engine, and of the methods available, or possibly available, to reduce the amount of this now immense waste of heat, is, in some respects, quite new, and is equally novel in the method of its presentation. The portraits with which the book is well furnished are believed to be authentic, and, it is hoped, will lend interest, if not adding to the real value of the work. Among other works which have been of great assistance to the author, and will be found, perhaps, equally valuable to some of the readers of this little treatise, are several to which reference has not been made in the text. Among them the following are deserving of special mention: Zeuner's "Wärmetheorie," the treatises of Stewart and of Maxwell, and McCulloch's "Mechanical Theory of Heat," a short but thoroughly logical and exact mathematical treatise; Cotterill's "Steam-Engine considered as a Heat-Engine," a more extended work on the same subject, which will be found an excellent companion to, and commentary upon, Rankine's "Steam-Engine and Prime Movers," which is the standard treatise on the theory of the steam-engine. The works of Bourne, of Holley, of Clarke, and of Forney, are standards on the practical every-day matters of steam-engine construction and management. The author is almost daily in receipt of inquiries which indicate that the above remarks will be of service to very many young engineers, as well as to many to whom the steam-engine is of interest from a more purely scientific point of view. CONTENTS. CHAPTER I. THE STEAM-ENGINE AS A SIMPLE MACHINE. PAGE SECTION I.--THE PERIOD OF SPECULATION--FROM HERO TO WORCESTER, B. C. 200 TO A. D. 1650 1 Introduction--the Importance of the Steam-Engine, 1; Hero and his Treatise on Pneumatics, 4; Hero's Engines, B. C. 200, 8; William of Malmesbury on Steam, A. D. 1150, 10; Hieronymus Cardan on Steam and the Vacuum, 10; Malthesius on the Power of Steam, A. D. 1571, 10; Jacob Besson on the Generation of Steam, A. D. 1578, 11; Ramelli's Work on Machines, A. D. 1588, 11; Leonardo da Vinci on the Steam-Gun, 12; Blasco de Garay's Steamer, A. D. 1543, 12; Battista della Porta's Steam-Engine, A. D. 1601, 13; Florence Rivault on the Force of Steam, A. D. 1608, 15; Solomon de Caus's Apparatus, A. D. 1615, 16; Giovanni Branca's Steam-Engine, A. D. 1629, 16; David Ramseye's Inventions, A. D. 1630, 17; Bishop John Wilkins's Schemes, A. D. 1648, 18; Kircher's Apparatus, 19. SECTION II.--THE PERIOD OF APPLICATION--WORCESTER, PAPIN, AND SAVERY 19