129400 MAY 21 1909 TJD •G99 E 6960180 INTRODUCTION. THERE exists no special work on Locomotive Engines. Two writers, Wood and Tredgold,* have indeed, in England, slightly touched upon that matter, but only in a subordinate manner, in treatises on railways; and, besides, they both wrote at a time when the art was scarcely beyond its birth. Consequently their ideas, their calculations, and even the experiments they describe, have hardly any relation to the facts which actually pass before our eyes, and can be of no * · A Practical Treatise on Railroads, and Interior Communication in general, by Nicholas Wood.' 1st edition, London, 1825; 2d edition, London, 1832. 'A Practical Treatise on Railroads and Carriages, by Thomas Tredgold.' London, 1825. use to such as wish to acquire a knowledge of these engines and their employ on rail ways. Many questions had not even been entered into, others had been solved in a faulty manner. New researches on the subject became therefore indispensable. This work will, in consequence, be found completely different from anything that has been published hitherto. No facts will be quoted, but such as result from actual observation; no experiments related, but those made by the author himself, on a new plan, and with new aims; finally, no theory exposed, but such as is derived from those experiments. If at first sight it appear astonishing, that no theory of Locomotive Engines should exist, the surprise ceases on considering that the theory of the steam-engine itself, taken in general, has not yet been explained. It was natural to suppose, that, respecting a machine In at present in such universal use, and on a subject of such importance, everything had been said, and every explanation given long ago. Far from this being the case, however, not even the mode of action of the steam in these engines has been elucidated. the absence of such indispensable knowledge, all theoretical calculations were impossible. Suppositions were put in the place of facts. In consequence, we have seen very able mathematicians propose, on the motion of the piston in steam-engines, analytical formulæ, which would certainly be exact, if all things went on in the engine as they suppose; but which not being founded on a true basis, fall naturally to the ground, in presence of facts. From this also results that, in practice, the proportions of the engines have only been determined by repeated trials, and that the art of constructing them has proceeded hitherto in the dark, and by imitation. Locomotive Engines being first of all steam-engines, we cannot advance in the researches we undertake, without solving at the same time the question relating to steamengines in general. There is even a remarkable point to be observed, which is, that of all sorts of steam-engines, locomotive ones are those which in their application have to overcome the least complicated resistance, and the most susceptible of a rigorous appreciation. This circumstance renders them therefore more proper than any others, for furnishing an explanation of general facts common to all those machines. The theory once satisfactorily established in regard to Locomotive Engines, will, of course, apply equally to all sorts of steam-engines, and more especially to those which, like locomotive ones, work at a high pressure. We flatter ourselves, therefore, that our researches, although apparently confined to Locomotive Engines, may at the same time |