"The reconversion of steam into water, or, as it is technically called, the condensation of steam, is, however, by no means necessary to the effective operation of a steam-engine. From what has been above said, it will be understood, that this effect relieves the piston of a part of the resistance which is opposed to its motion. If that part of the resistance were not removed, the pressure of steam, acting upon the other side, would be affected in no other way than by having a greater load or resistance to overcome; and if that pressure were proportionately increased, the effective power of the machine would remain the same. It follows, therefore, that, if the steam upon that side of the piston towards which the motion is made were not condensed, the steam, urging the piston forwards on the other side, would require to have a degree of intensity, greater than the steam in a low-pressure engine, by the amount of the pressure of the uncondensed steam on the other side of the piston."

"An engine, working on this principle, has therefore been called a high-pressure engine. Such an engine is relieved from the incumbrance of all the condensing apparatus, and of the large supply of cold water necessary for the reduction of steam to the liquid form; for, instead of being so reduced, the steam is in this case simply allowed to escape into the atmosphere. The operation, therefore, of high-pressure engines will be readily understood. The boiler, producing steam of a very powerful pressure, is placed in communication with a cylinder, furnished, in the usual manner, with a piston; the steam is allowed to act upon one side of the piston, so as to impel it from the one end of the cylinder to the other. When it has arrived there, the communication with the boiler is reversed, and the steam the cylinder to the condenser, E; F, air-pump, which removes the water and air from the condenser; G G, cistern of cold water, surrounding the condenser; H H, pump which supplies the cistern, G, with cold water; I, cistern containing hot water, from the condenser; K, pump to convey the hot water from the cistern, I, to the boiler, A.

is introduced on the other side of the piston, while the steam, which has just urged the piston forwards, is permitted to escape into the atmosphere. It is evident, that the only resistance to the motion of the piston, here, is the pressure of that portion of steam, which does not escape into the air; which pressure will be equal to that of the air itself, inasmuch as the steam will continue to escape from the cylinder, as long as its elastic force exceeds that of the atmosphere. In this manner, the alternate motion of the piston in the cylinder will be continued; the efficient force which urges it being estimated by the excess of the actual pressure of the steam from the boiler above the atmospheric pressure. The superior simplicity and lightness of the high-pressure engine must now be apparent; and these qualities recommend it strongly for all purposes in which the engine itself must be moved from place to place."*

Mr. Gordon an engineer thus enumerates some of the applications of this plastic power, when treating of the substitution, in England, of inanimate for animate power, in locomotion. "Considered in its application to husbandry, the cottager looks forth upon the neat paling which fences his dwelling; it was sawed by steam. The spade with which he digs his garden, the rake, the hoe, the pick-axe, the scythe, the sickle,—every implement of rural toil which ministers to his necessities, are produced by steam. Steam bruises the oil-cake which feeds the farmer's cattle; moulds the ploughshare which overturns his fields; forms the shears which clip his flock; and cards, spins, and weaves, the produce.

"Applied to architecture, we find the Briarean arms of the steam-engine every where at work. Stone is cut by it, marble polished, cement ground, mortar mixed, floors sawed, doors planed, chimney-pieces carved, lead rolled for roofs and drawn for gutters, rails formed, gratings and bolts forged, paints ground and mixed,

* See Edinburgh Review, No. 111, art. Inland Transportation. In Fig. 17, on the next page, a view of the internal construction of a locomotive high-pressure steam-engine will enable the reader the bet

paper made and stained, worsted dyed and carpet wove, mahogany veneered, door-locks ornamented, curtains and furniture made, printed, and measured; fringes, tas

sels, and bell-ropes, chair-covers and chair-nails, bellwires, linens, and blankets, manufactured; china and earthen-ware turned; glass cut, and pier-glass formed; the drawing-room, dining-room, kitchen, pantry, closets, &c., all owe to steam their most essential requisites.

ter to understand this description. BB, boiler; C, chimney; D, door by which fuel is introduced to the fire, F; P, Piston; S, steam-pipe.

"Should the question be asked, what has enabled the inferior proprietors to wear two hats a year instead of going bare-headed or sporting the bonnet which their fathers wore; what has clothed them in suits of excellent broadcloth, and given them ability to ruffle it with the first-born of the land; what has donned for their wives, ladies' apparel, made their boys rejoice in a plurality of suits; and, in the bridal hour, busked their daughters in robes, delicate in texture as the spider's web, beautiful in color as the rainbow's hues, and for elegance such as never in their grandame's younger days, even Duchesses wore; what plaited her bonnet, tamboured her net, wove her laces, knitted her stockings, veneered her comb, flowered her ribands, gilded her buttons, sewed her shoes, and even fashioned the rosette that ornamented their ties? The answer is,-steam."

We have thus shown, how heat may be employed in producing motion. It may be proper to remark, in concluding the subject, that this is not the only nor perhaps the most important use, to which that powerful agent may be applied in the arts. Heat forms an almost universal fuser, which enables us to reduce the most refractory substances, and to overcome degrees of cohesion which seem to defy every other agency. It serves not only to prepare our food and warm our habitations, but also to smelt ores, and render metals malleable; to harden clay for the various uses of the builder and the housekeeper; and to extract, from mixtures of alkali and sand, that beautiful substance, which decorates our tables, reflects our persons, and guides the feeble vision of age and infirmity over the page of wisdom, and in the pursuits of industry.

To procure this principle, therefore, by artificial means, and to apply it to the various purposes of life, must be one of the most important and comprehensive of all the arts. It is an art, however, which has received comparatively but little attention. The chemical laws of heat have been investigated, with equal ingenuity and success. But the application of these laws to the pro

cess of producing and using heat has been less studied, and has by no means made the progress, which might have been anticipated, from its importance. One reason of it may be, that mankind have been so long employed in building fires, and applying heat to its various uses, that they cannot be persuaded that they need instruction in regard to a subject so familiar; and they are slow, therefore, to study it on strict and philosophical principles. Another reason undoubtedly is, that we are usually so engrossed with the object to be attained by the use of heat, and have reason to be so well satisfied with our success, that we have felt little temptation to scrutinize the means employed. Still, it is an unquestionable truth, that the economy of heat has not yet passed its infancy, and is probably destined to undergo a great, and, if we mistake not, a speedy, revolution. It will be our object, in the remaining paragraph of this Chapter, to state some of the defects which appear to characterize this art, in its present state, and some of the most important objects which appear to be still unattained, at least in ordinary instruments.

The greatest want, connected with the practical economy of heat, is that of fixed principles, to regulate the construction of furnaces and other instruments. They are now too generally made at random, or according to rules which have been established only by custom, and for which no sufficient reason can be assigned. The true basis, on which all such constructions should rest, must be found, it is presumed, in the discoveries which have been made by chemical philosophers, respecting the different radiating and conducting powers of various substances and surfaces, as well as respecting the nature of combustion and the capacity of certain principles for supporting it. These, if properly considered, would suggest the requisite conditions for generating heat, which must always be the same; and also the proper means of applying or using it, which should evidently vary, with the object to be attained. Not the least among the errors which are generally commit