In the compilation of the foregoing narrative of the origin and progress of the steam-engine the most standard authorities have been consulted. In describing the various engines selected for illustration, the words of the several inventors have been adhered to u closely u possible ; and where the commentaries of early historians have become, u it were, identified with the explanations given, it was considered preferable to adopt their own expressions, than by clothing them in other language, to affect an air of false originality. The writings of Mr. Farey, Mr. Stuart, and other able investigators, have, in occasional instances, been made tributary to the more clear and lucid explication of the particulate upon which they were resorted to for information.
Those readers who may desire toacquaint thliniselves with the various modifi cations of the engine by other and later inventors, will find in the Appendix to Galloway and Hebert's History a more extensive account then is contained in any other published work.
In other parts of this Encyclopteclia, under their several tides, are described various modifications of the constituent parts of the mechanism of steam-engines; inch se Boilers,. Valves, Pistons, Parallel Motion, fire. the absence of which in
this place impairs, perhaps, the completeness of the descriptions given; but, for the reason just aseigned, their introduction was unnecessary. The numerous inventions of steam wheele and rotary es have been very slightly alluded to, because, although much ingenuity islssyed in their contrivance, yet, as regards the greater number, practical trials LLaave not corroborated the opinions at first entertained of their utility; it was therefore thought better to allot the space which a description of them would have occupied, to more practically im portant matter. The other motive powers which usually receive incidental notice in works on the Steam-Engine—such as the gas vacuum, alcohol, air-engines, firc., are described under their respective heads in this work; for which see their initial letters.