balances several pounds by moving it further from the fulcrum, still it is only a pound with the force of one. So a pound of steam can no more do the work of two pounds than a pound of metal-no more than one horse can do the work of two horses. The pressure within a boiler increases with increased accumulation of steam.

4. The terms condense, condensation, &c., are apt to convey, to some minds, the same idea as when applied to solid bodies, as rendering metals more dense by hammering or when passed through rollers; whereas, here they indicate the production of a void by the vapor shrinking into a minute part of the space it filled—as gallons of steam into thimblefuls of water.

The foregoing borne in mind, all that follows may be understood by others than practical men. They will perceive two forces in steam, of which one begins to act as the other ends; and that its power continues from its birth in the boiler to its last gasp in the condenser. Moreover, that heat is the element of force and steam the agent or medium by which it acts, and consequently fuel only is consumed and has to be renewed. A small quantity of water might furnish an indefinite amount of steam. Being revived in the boiler as fast as it expired in the condenser it might circulate through them forever.

The great lever of modern civilization and essential to its progress, steam has immeasurably more work to do than it has done. It has to be cheapened, and to effect that more work has to be got out of it. Rich in that which is the source of all wealth, its economical applications are among the most important desiderata; for the fact is incontrovertible, though almost incredible, that not over one-third of its power has yet been utilized, consequently two-thirds of the fuel expended upon it are lost.

Like the permanent gases, steam is a fluid spring, differing from solid ones in the form of its action. Instead of bending to and fro, it swells and shrinks. In the range of its movements it surpasses those made of metal. They are derived from ores; it comes from water, of which one volume swells into seventeen hundred and shrinks back into one. No clearer idea of its capacity and functions can be had than by considering it as an elastic instrument of motion. Heat winds it up and cold unwinds it. Like other springs it has two movements, equal in power, but in opposite directions, and both must be used. To neglect either is to lose half of the power. For highpressure motors the spring is wound up and allowed to run down to waste, while for an atmospheric one the shrinking movement is used and the swelling one passed by as if of no account.

There can therefore be no doubt, however valuable atmospheric engines may be for particular purposes, that the truest application of steam, as an agent of force, is to associate high pressure engines, the greatest wasters of it, with atmospheric ones which blow off none. All the heat will then be utilized, and when that is done practice will conform to theory and be perfect.

As the two movements or forces bear the same relation to each other as action and reaction, if the amount of one be ascertained it

must be the same as that of the other; hence if the expansive power is not easily traced to the vanishing point, we know exactly what it is by the vacuum condensation produces. They have given rise to two classes of engines, high-pressure or non-condensers and conden

sers.

Non-condensing engines, the most numerous and popular, are operated solely by the swelling or expansive force, and consequently cannot turn to account more than half the power in it. They do not, however, do that nor anything like it. There is a mechanical difficulty in the way, the consequence of which is that they utilize only about half the expansive force, and therefore only one-fourth of the power. A cubic inch of water evaporated under a piston raises a ton a foot high; there the force and resistance are balanced, and there the piston of the engine stops; the force remaining in the fluid being dispersed with it for lack of means to use it. A steel spring half uncoiled can be removed and its unexpended force employed, but engineers do not yet know how to do that with steam that has spent part of its force in the cylinder of an engine.

To lessen the loss, most engines "work steam expansively." That is, the cylinder is only partially charged, by cutting off the communication with the boiler at certain stages of the stroke, the portion admitted being left to dilate and follow up the piston to the end of the stroke. The alleged gain from this arrangement is considerable. It would be complete instead of partial if expansile and contractile pistons, working in conical instead of cylindrical chambers, could be used, as they would present enlarging areas to decreasing pressures, and receive and impart a full and equable effect from a varying force. The device, however, is apparently not within the range of our present mechanical appliances.

The amounts of expansive force escaping in the volumes of waste steam from high pressure engines are obvious. Whether the European estimate of this loss be exaggerated or not, the fluid goes through such as make 50 strokes and upwards per minute, with great rapidity. The piston acts but as a momentary check on its passage from the boiler to the waste-pipe. The temperature and amount can be but little reduced.

Of the vast and increasing numbers of high-pressure engines there is perhaps not one proprietor in a hundred prepared to believe that in his waste pipe he throws away as much power as he realizes; and if next told that the amount is nearer twice as much, derision would probably succeed to incredulity. The clouds of steam ascending daily from engines located on the East and North Rivers, afford such proofs of economy, as dumping off the docks half the quantity of coal consumed in heating their boilers would be.

Condensing Engines.-These call into action both forces, and, strange to say, they yield little more than half of one of them; and this, too, in the face of the fact that, while there is a difficulty in the way of obtaining the entire expansive force, there is none whatever in realizing by condensation the whole of the contracting force. Lard

ner, in his work on the Steam Engine, thus speaks of both classes :— "In engines which do not condense the steam, and which, therefore, work with steam of igh pressure, some of the sources of waste are absent, but others at of increased amount. If we suppose the total effective force of the water evaporated per hour in the boiler to be expressed by 1000, it is calculated that the waste in a high-pressure engine will be expressed by the number 392; or, in other words, taking the whole undiminished force obtained by evaporation as expressed by 10, very nearly four of these parts will be consumed in moving the engine, and the other six only will be available.

"In a single acting condensing engine, taking, as before, 1000 to express the total mechanical power of the water evaporated in the boiler, 402 will express the part of this consumed in moving the engine, and 598 therefore will express the portion of the power available; or taking round numbers, we shall have the same result as in the non-condensing engine, viz: the whole force of the water evaporated being expressed by 10, 4 will express the waste and 6 the available part.

"In a double acting condensing engine, the available part of the power bears a somewhat greater proportion to the whole. Taking, as before, 1000 to express the whole force of the water evaporated, 368 will express the proportion of the force expended on the engine, and 632 the proportion which is available for the work.

"In general, then, taking round numbers, we may consider that the mechanical force of four-tenths of the water evaporated in the boiler is intercepted by the engine. In this calculation, however, the resistance produced in the condensing engine by the uncondensed steam is not taken in the account: the amount of this force will depend on the temperature at which the water is maintained in the condenser. If this water be kept at the temperature of 120°, the vapor arising from it will have a pressure expressed by three inches seventenths of mercury; if we suppose the pressure of steam in the boiler to be measured by 37 inches of mercury then the resistance from the uncondensed steam will amount to one-tenth of the whole power of the boiler; this added to the four-tenths already accounted for, would show a waste amounting to half the whole power of the boiler, and consequently only half the water evaporated would be available as a moving power.

"If the temperature of the condenser be kept down to 100° then the pressure of the uncondensed steam will be expressed by two inches of mercury, and the loss of power consequent upon it would amount to a proportionately less fraction of the whole.' Again, "If the direct force of high pressure steam be combined with the indirect force produced by its condensation, the total mechanical effect will be precisely equal to the mechanical effect of the condensation of atmospheric

steam.'

That is, six-tenths is the sole practical value of each of the forces, and of both combined! Less than one-third of both. Whereas, if the contracting force did not disappear, somehow or other, in the engine,

the result should and would be over two-thirds instead of less than

one.

Hence the question naturally arises-If condensing engines produce no more power than non-condensing ones, why employ them at an increased expense of machinery and of power intercepted by it; and if the expanding and contracting forces produce, when combined, only the effect of one, why use them in combination? Is there not something here that wants explaining? Force within an engine that does not come out must be absorbed by the mechanism or neutralized by its arrangement. We know that separately the two forces act perfectly, and hence when their united effect is not double that of one of them, it can only be ascribed to their combination.

There is no difficulty in collecting separate forces into one motive power, like affluents of a river into a single channel, when they coincide in their bearing or course, but it is otherwise when they move in opposite directions. To make such coalesce they must be separately evolved. How can two conflicting ones as heat and cold, shrinking and swelling, be combined without their joint effect being less than their separate action? Can anything be more certain, than that steam discharged from a non-condensing engine will, as readily as direct from a boiler, produce as much more power if passed into an atmospheric cylinder? Compact machinery is a favorite doctrine, but it may be carried too far. The condensing steam engine is an example.

Heat not used up is wasted, but theory tells us it ought to be wholly utilized. How is that to be done? In the way that nature does it by first using the expansive force and then deriving an equal amount from contraction.

Now, while the indirect force of steam in shrinking into a liquid equals its direct pressure against a piston, how is it that condensing engines are not more productive? Because they condense compressed steam, and limit the effect of the vacuum to the area of the piston. Perhaps it will be said that when an engine is worked with 30 or 60 pound steam it does not follow that such is its tension on leaving the cylinder, since in most cases it is reduced by expansion through the operation of the cut-off. Granted; yet it cannot be reduced below the resistance, so that at whatever tension it is above that of atmospheric vapor, just so much is wasted, so much power thrown away. But suppose it dilated till barely sufficient to balance the atmosphere; what then? would not the effect be the same as long as the vacuum is confined to the piston? If several cubic feet of common steam be compressed into a cubic foot, would not each, on being released, swell into its previous volume and be as valuable for producing a vacuum in a working cylinder of the capacity of a cubic foot as the condensation of the whole of them in it? That is what our engines should be made to do; instead of which they extinguish the life in several volumes for the sake of one, and consequently get no more than the effect of one out of them. This is that which enfeebles them, nor can it be removed except by using steam too weak to move the piston at all. It is ex

pensive as well as inherent; for in condensing more than is necessary there is a loss of power, and a loss that increases with the excess. It would be better to blow off the surplus, if that could be done, than to waste power over it. Such is the result of a misalliance, or vicious combination, of expansion and collapsion in the same cylinder.

Is it asked how the evil is to be avoided? By cutting off the communication between the condenser and working cylinder, and discharging the steam from the latter into an atmospheric one, its capacity being determined by the intended pressure of the steam, or the number of times it will admit the working cylinderful of high or compressed steam to expand into low, or uncompressed. Thus, an engine working with 60 Ibs on the inch, one cylinderful would expand into four at common or atmospheric pressure, at 90 lbs into six, at 120 lbs into eight, at 150 lbs into ten. Whatever the number, it will be found that the force evolved by condensation is equal to that of expansion. For example, a cylinder working with steam of 60 lbs. and the area of the piston 50 square inches, the expansive pressure will be 60 X 503000 lbs. On the other hand the fluid would fill four cylinders of the same dimensions, or one with a piston of four times the area; hence 50 X 4 X 15-3000 lbs. of atmospheric pressure. By the present system the vacuum, instead of yielding 3000 lbs., would probably not yield 300. According to the authority quoted -which has not been questioned-it would yield little or none.

Whatever other advantages may be claimed for the condenser of Watt, as respects economy of power it was a decided failure-the continued use of which can only be accounted for on the ground of passive and unreflecting obedience to his rules. He appears to have been embarrassed by the claims of the two opposite forces, and made a compromise between them instead of giving each its full scope by itself. The air-pump crippled both. It took steam to work it, and produced no better vacuum than Newcomen had without it. It checked the employment of high and even steam of medium pressure. But for it, he would have made more manifest an alleged preference of the expansive over the contracting power. A philosphical friend gave currency to the statement, that his condenser was originally suggested as an economical appendage to Newcomen's engine. This he contradicted, saying: "From the first I intended to operate with steam instead of the atmosphere, and my apparatus was so constructed." (Stuart's Anecdotes of Steam engines.)

Notwithstanding this, "the three great steps in the brilliant career which has immortalized his name," had every one of them reference to atmospheric pressure: 1. Condensing in a separate chamber was to avoid the cooling of the cylinder by the jet playing in it. 2. Maintaining the vacuum by the air-pump and its accompanying hot and cold water pumps. 3. Closing the open end of the cylinder to avoid the cooling effects of the air on pushing down the piston, and requiring, as in the case of the jet, more steam on the ascent of the piston to reheat it.

The leading inquiry in discussing the value of motive forces is not what power is got out of one, but how much can be got out of it. We