Although the plan of this new edition of Beckmann's 'History of Inventions and Discoveries' was to confine it to the subjects treated of in the original work, yet we feel it imperative to make an exception in favour of the Steam-Engine, the most important of all modern inventions. The power of steam was not entirely unknown to the ancients, but before the æra rendered memorable by the discoveries of James Watt, the steam-engine, which has since become the object of such universal interest, was a machine of extremely limited power, inferior in importance and usefulness to most other mechanical agents used as prime movers. Hero of Alexandria, who lived about 120 years before the birth of Christ, has left us the description of a machine, in which a continued rotatory motion was imparted to an axis by a blast of steam issuing from lateral orifices in arms placed at right angles to it.