TREATISE ON THE MECHANICAL MEANS BY WHICH VESSELS ARE PROPELLED BY STEAM POWER. BY WILLIAM HALE, C.E. LONDON: LONGMANS, GREEN, AND CO. 1868. 186. e. 24. PREFACE. IN PAST AGES, the light of science was communicated only to a few, but the present is an epoch remarkable for a great influx of light, and the progress of improvement in science and art is comparatively little impeded by the ignorant prejudice which formerly resisted every innovation. The amazing discoveries that have been made in chemistry, and the various mechanical inventions that have been devised, especially within the last few years, constitute a study worthy of the most intelligent minds; not only from the great interest attaching to them on their own account, but also from the question they suggest, as to their ultimate effect upon the welfare of mankind. Within this century their effect has been so great, that the present condition of the world, as contrasted with former periods of its history, may be compared to the dawn of day breaking forth from the obscurity of night. So widely and so rapidly is knowledge being diffused, that on all sides, we are reminded, that the night of ignorance is passing away, and we may anticipate, that discovery and invention which have already revealed such wonders, will yet make manifest others which would in our forefathers' time have been deemed impossible, without an alteration in the natural laws and constitution of things. The system of locomotion, especially, is now so changed, that a multitude of people can travel by land more rapidly, and with greater ease and comfort, from one country to another, than a few could formerly from county to county. The speed to be attained in travelling, as also the weight to be transported, were limited by, and wholly dependent on, the capabilities and endurance of the horse; but now that noble animal's power is superseded by the mighty agency of steam, which, in the speed to be obtained and the weight to be carried, is hardly to be limited. More than a thousand passengers can now be conveyed in one train, with a velocity equalling that of the flight of the swiftest bird; while the weightiest masses of goods, &c., can be transported with similar speed. Roads are not now, as formerly, constructed of earth and rough stones, but of smooth iron, made straight and level as a plain. Valleys are raised, and mountains and hills made low; and a pathway is being opened everywhere, for the more complete |