dumb and the blind. It has 2 weekly newspapers, 10 or 12 churches, several banks and banking houses, 2 academies, and 2 seminaries. It is surrounded by a populous and rich agricultural region, and has an important local trade. There are mills, founderies, and manufactories of various kinds. The Virginia central railroad passes through it, and it is the proposed terminus of the Manassas Gap railroad, partially completed.

STAUNTON, SIE GEORGE LEONARD, an English diplomatist, born in Galway, Ireland, April 19, 1737, died in London, Jan. 14, 1801. He studied medicine and became a contributor to literary periodicals, and an intimate acquaintance of Dr. Johnson. He afterward held official position and practised medicine in the West Indies for several years. In 1774 he was attorney-general of Grenada, and when that island was taken by the French in 1779, he and Lord Macartney, the governor, were made prisoners, but were soon released and returned to England. In 1781 he went as confidential secretary of Lord Macartney to Madras. He made an advantageous treaty with Tippoo Sultan in 1784, for which he was raised to a baronetcy and received an annuity of £500 from the East India company. He was a member of Lord Macartney's embassy to China in 1792, of which he published an account (2 vols. 4to., 1797).—SIR GEORGE THOMAS, an English author, son of the preceding, born in Salisbury, May 26, 1781, died in London, Aug. 10, 1859. He accompanied his father to China in 1792, entered the university of Cambridge on his return to England, and in 1799 went to Canton as secretary of the East India company's factory there, of which he afterward became president. In 1816 he was attached to Lord Amherst's embassy to China, and from 1818 to 1852, with a few intermissions, was a member of parliament. His principal works are: "The Penal Code of the Chinese Empire" (4to., London, 1810); "Narrative of the Chinese Embassy to the Tartar Khan Tourgouth during the Years 1812'15" (1821); and "Miscellaneous Notices relative to China and the British Commercial Intercourse with that Country" (1822). A treatise on vaccination written by him in Chinese was the means of introducing its practice in some parts of the empire. He edited the "History of the Great and Mighty Kingdom of China," translated from the Spanish of Mendoza by Parke in 1588 (Hakluyt society, London, 1853).

STAUPITZ, JOHANN VON, the friend and patron of Luther, born at Meissen, died in 1524. He entered in early life the Augustinian order, obtained from the pope in 1501 general privileges for the newly established university at Wittenberg, and in 1508 by his influence caused Luther, a member of his order, to be called to one of the professorships. Luther gratefully acknowledges that in his spiritual struggles he found in Staupitz a kind adviser and guide. Staupitz

approved of the theses of Luther against the papal indulgences, though he did not publicly declare himself in favor of them. In 1518 he was with Luther at an assembly of his order at Heidelberg, and in the same year demanded at Augsburg that Luther should not be condemned unheard and untried. Soon after, however, fearing an adverse issue of the controversy, he withdrew to Saltzburg, where he became court preacher, and in 1522 abbot of a Benedictine convent. Whether, as some assert, he was shortly before his death bishop of Chiemsee, is doubtful. He is the author of two works, De Amore Dei and De Fide Christiana, in which a mystic tendency prevails.

STEALING. See LARCENY.

STEAM, the name applied generically to the vapor or non-permanent gas given off by any liquid, in consequence of the volatility of such liquid and the influence of heat upon it; and more especially when the vaporization takes place at temperatures at or above the boiling point of the substance so affected. In the recent progress of mechanical art and science, however, this term has come to designate in a specific sense the vapor of water, as applied or applicable to the performance of work, or to other mechanical or economic purposes. In connection with this subject see BOILING POINT, EVAPORATION, HEAT, and PNEUMATICS. In popular language, the visible mist forming when a vapor is discharged into the air, as a little way from the spout of a boiling kettle, or in a dense cloud above an engine "blowing off" steam, is also called steam. This visible mist is, however, really of the nature of cloud; being probably a collection in immense numbers of minute vesicles formed of water condensed from the vapor, and also enclosing vapor or air, and which, disseminated in the atmosphere, constitute an opaque and visible mass, in the same way as do the fine globules of a transparent oil when the latter is beaten up and mingled through water. Steam, properly so called, is perfectly transparent and colorless, as are the greater number of gases of all sorts; and hence it is always wholly invisible. Whenever a confined body or other volume of steam seems to become visible, the truth is that a portion of the vapor is condensed into water in fine drops, or in a haze or cloud; and though there may also be steam occupying the space through which this is diffused, it is the water or cloud only that is seen. The engineer and the general reader have thus alike to bear in mind that, in dealing with steam (proper), they have to do with a gaseous body which eludes the sight as completely as the purest atmospheric air. Perfect steam is, moreover, in no way moist, but is dry, as are the permanent gases; the moisture sometimes showing upon a solid surface it touches, or that has been plunged into it, being due to condensation. With such slight exceptions as are hereafter to be noted, steam has in a complete degree those properties of fluidity, mobility, elasticity, and equality of pressure in every

direction about any point in a volume of it at rest, that distinguish the gases; and in consequence of which it is brought under the ordinary laws of pressure, equilibrium, and movement of gaseous fluids, as given in the article PNEUMATICS. At the same time, the rapidity with which, at a given condition and temperature, it can be condensed, or again formed, and the great disturbances in its heat and elastic force or pressure that occur at the moments of such changes, strikingly distinguish it from the permanent gases, and in fact impart to it its peculiar fitness as a medium through which to apply the motive power of heat.-It will be remembered that the agency we call heat exists free in all bodies upon and about our globe; and that, whenever in any body or space an excess of this free heat is in any way caused to appear, as by combustion of wood or coal, or the action of the sun's rays, this excess at once tends to be imparted to and equalized throughout surrounding bodies and spaces, at such rates as the nature of the latter, their surfaces, &c., will allow; while, if at any place a reduction of heat occurs, the surrounding bodies and spaces impart heat to this, and again with a rapidity depending on their nature and the character of the surfaces separating or bounding them. Now, between the particles of all fluids there is acting at all times a repulsive force or energy, greater or less, tending to drive the particles asunder; if the body be a liquid, to throw it into the gaseous condition; if a gas, to enlarge still further its volume. It is this repulsive energy that, as we pump off the surrounding atmosphere from about a tight bladder holding a little air and placed in the receiver of an air pump, goes on distending the bladder, till it may even burst it from within outward. The repulsive action in these bodies is moreover known to be either directly that of heat, or such as heat directly conspires with and augments. And as the small body of air confined in the bladder is, in the atmosphere, kept by pressure of the surrounding air within a moderate volume, so it is found also that a vast number of liquids-those termed volatile-at any ordinary temperatures owe their liquid state to the superincumbent pressure of the atmosphere upon their surfaces. Water is, for all temperatures above its freezing point, a perfectly volatile liquid; so that if we should introduce a pint of it, at any temperature from 212° down to 32°, into a perfectly vacuous space large enough to contain the resulting perfect vapor, the whole of the liquid would vaporize instantly and disappear in the gaseous form. The only other condition necessary to this result is, that the bodies in contact with the liquid when introduced shall be able to yield to it a sufficient amount of heat to convert it as stated; this heat becoming latent in the vapor, and the bodies parting with it becoming correspondingly cooled. In so vaporizing the water, also, as the temperature taken for the change was lowered, the vapor itself when

formed would have a feebler elastic tension, and would be less dense; so that a larger vacuous space must be continually provided as we approach 32°, to insure the rapid and complete volatilizing of the liquid. But if into the vacuum some air were introduced, and the experiment repeated, the vaporization of the liquid would be retarded, and more-finally even to nearly preventing it altogether-as the density and pressure of the admitted air were increased. This repressive effect of the incumbent air, however, could always be overcome by artificially applying a sufficient degree of heat to the liquid. And when the atmospheric pressure equalled its average at the sea level, 14.7 lbs. avoirdupois to the square inch of surface, if heat sufficient could be supplied, any quantity whatever of water would still vaporize and become steam instantly, against and in spite of such pressure, at the moment when the temperature of the entire liquid mass became raised to 212°. Thus, while evaporation takes place slowly at all temperatures, down to and below zero of Fahrenheit, giving vapor of feebler tension and less density-the tension at 0° equalling inch of mercury-a vaporization of whole volumes of liquid (larger or smaller, according to the facility with which the requisite heat can be supplied to enter into the latent form, or give to the resulting vapor its tension) must commence in any body of water or other liquid so soon as the tension of its vapor is made equal to the pressure of air or other gaseous bodies upon the surface of the liquid. It is this tumultuous vaporization that we call boiling; its rate being really slow, and the process prolonged, only (and fortunately, in view of the risk otherwise of continual explosions) by reason of the fact that but a limited and gradual supply of heat can, under any circumstances, be made to enter the liquid. The principal fact here, and the one never to be lost sight of, is, that any liquid in ordinary conditions vaporizes in volumes, i. e., boils, at the precise moment when the tension of its vapor due to heat has risen to an equality with the pressure of that atmosphere, whether of common air, or of confined vapor already formed, which rests or presses upon its surface. And no matter how the vapor forming is in the main enclosed, if there be but one small aperture in the boiler, the cylinder, or other passages, through which the atmosphere without can transmit its pressure, and any excess of vapor within above that pressure can escape, it is still the atmospheric pressure precisely that acts upon the liquid surface. Hence it is seen that, the character of the vessel and other conditions being like, and the incumbent pressure the same, the temperature of ebullition of the liquid remains always the same; that under a given pressure the temperature of the liquid remains constant through the whole period of the ebullition, a greater quantity of heat communicated to the liquid having only the effect to evolve during a given time a larger volume of steam; that

the elastic force or tension of steam forming at 212° F. is precisely equal to the weight of the superincumbent atmosphere, or very nearly 14.7 lbs. per square inch; and that when, by confining the vapor obtained, its density and pressure are increased, a higher temperature becomes necessary to secure ebullition, and we say that the boiling point is raised. Steam forming by boiling at 212° is thus said to have a tension or pressure of 1 atmosphere; at 234°, of 13 atmospheres; at 250°, 2; at 264°, 21; at 274°, 8; at 292°, 4; at 306°, 5; at 340°, 8; at 357°, 10; at 389, 15; and at 415°, 20 atmospheres, or about 294 lbs. per square inch. Generally, as produced over or in communication with water of its own temperature at the moment of its formation, steam is at its maximum of density for the temperature, whatever that may be. Under such circumstances, however, the steam mass owes a part of its actual density to the holding of more or less of finely divided water or mist in suspension through it. In whatever its density may consist, the greatest pressure under which steam can exist at a given temperature, as steam, is also the least pressure under which water similarly heated can retain the liquid form. This is called, for the given temperature, the pressure of saturation; and the steam is said to be saturated. On the other hand, steam refuses to generate freely or in volumes with less than this maximum quantity of vapor. That is, steam and water thus conditioned are, so to speak, at an equipoise; increase of heat will increase the quantity of water vaporized, and so, in a confined space, the density of the vapor; or increase of pressure will compel a portion of the vapor already formed to resume the liquid state. The steam stands, at the same moment, at the condensing point and at the generating point; and in fact, throughout the entire range of heat, there will occur at every point, in unalterable conjunction, one density, one pressure, and one temperature; and always, the density being given, the other elements will correspond. Of course, when change in one of these particulars occurs, slight lapses of time must be allowed the others to adjust themselves to this; but the agreement of all the conditions just expressed is that to which the steam mass communicating with the water in the boiler is always tending. If from steam under more than one atmosphere of pressure, and the temperature and density of which are proportionally increased, some heat be withdrawn, the tension and hence the density fall, and part of the steam resumes the state of water. If, while the temperature remains constant, the space or volume over the water be increased, then, so long as there remains an excess of liquid to supply fresh vapor for the augmented space, the density and tension will not diminish, but remain constant at the maximum due to the given temperature. If, after all the liquid is evaporated, heat be not added to the steam mass, but the space or volume be enlarged, the steam expands, and its

density and pressure diminish, as in the permanent gases. If, then, the volume be again reduced, the density and pressure increase, until they return to the maximum due to the temperature, reaching the condensing point; and the effect of further diminution of volume must be precipitation or liquefaction of corresponding quantities of the vapor, the density remaining constant, and even until the whole mass of vapor had thus been forced back to the liquid condition. If, after all the liquid is evaporated, or a portion of it has been separated in any way from the water surface, the application of heat be continued, the state of saturation is left behind; and even if the same density be preserved, the tension or pressure is increased, though not so rapidly as if with the same increase of temperature the steam could remain in contact with the water, and so continue to maintain through this rise the condition of saturation. The steam so separated and heated loses the moisture which may accompany it in the saturated state, and at a few degrees of added temperature acquires in full the character of a perfect gas; it is then said to be surcharged with heat, and it is known as gaseous or subsaturated steam, more commonly as "superheated steam," and is by some writers termed "stame." Let steam in this condition be replaced in contact with the water in the boiler, or in any way brought into free communication with it-the water having yet the original temperature-and such steam would immediately evaporate and absorb a further portion of the water, transferring to this its excess of heat, and would become saturated, its temperature falling to that of the water.The relation, generally, of heat to the production of mechanical effect, or work, is considered under HEAT. The unit is the mechanical equivalent of the heat required to raise through 1° F. 1 lb. of water; and this, experiment seems to show, is 772 lbs. weight raised against gravity through 1 foot of height, i. e., 772 footpounds. If 1 lb. of water at 212° be injected into a vacuous space of 26.36 cubic feet-this being the volume of 1 lb. of saturated steam at that temperature-and if it be evaporated into such steam, there will be expended in the process 892.9 units of heat. Now let a second pound of water at 212° be injected into and evaporated in the same space; and this, having to assume its volume or advance against a pressure of 14.7 lbs. per square inch, will perform work to the amount of 26.36 × 144 × 14.7 lbs. = about 55,800 foot-pounds; and since 55900-72.3, this quotient will be the number of additional units of heat that must in such case be consumed or expended in displacing the first steam atmosphere, against which the second must advance; so that to convert the second pound of water into steam against this pressure will require 965.2 units of heat. When steam flows from the boiler into vacuous space, without performing work, its temperature, chiefly by reason of its friction against the