CONDENSING AND NON-CONDENSING ENGINES. 139

locomotive engines, steam-carriages, steam-vessels of alight and rapid construction, and such other purposes asrequire portability or cheapness. The latter is more com-plex, but more effective ; more expensive in original con-struction, but more durable and more economical in con-sumption of fuel. The first is more commonly in use inAmerica , the latter in this country. The high-pressureengine is sometimes also called the non-condensing steam-engine, to distinguish it from the low-pressure engine,which is also called the condensing steam-engine; butthere is sometimes a combination effected of some of theparts and principles of both these species, in what iscalled a high-pressure condensing engine, by which, forcertain purposes, the peculiar merits of both species arecombined in the same machine.

Of these two sorts of steam-engine, it is remarkablethat the more elementary and simple—that which is themore easily conceived and understood—was not inventedand brought into practical use until long after the otherkind had been very extensively used and made known byits inventor , James Watt . It appears to us, that we areto consider Oliver Evans of Philadelphia as the inventorof the modern high-pressure engine. Before 1786 hehad contrived and made experiments upon a high-pressureengine, which seems to have been in all essential respectssimilar to our own. Indeed, it appears that the Ameri-cans have taken the form and arrangements of theirengines from Evans , as implicitly as in this countrywe have adopted those of Watt . The history of Evans consists almost entirely of the romance of real life.Sanguine and energetic, he continually encountered diffi-culties only to overcome them, and to encounter re-