The Mirror of Literature, Amusement, and Instruction. Volume 20, No. 575, November 10, 1832

THE STEAM ENGINE SIMPLIFIED

It is a universal property of matter, that by the application of heat, so as to raise its temperature, it suffers an increase in its magnitude. Also in different substances, when certain temperatures are attained by the application of fire, or other methods of heating, they undergo a change of form. Solids, at certain temperatures, are converted into liquids; and liquids, in like manner, when heated to certain degrees, become aeriform fluids or gases. These changes are familiar to every one in the ordinary phenomena attending water. Below the temperature of 32° of the common thermometer, that substance exists in the solid form, and is called ice. Above that temperature it passes into the liquid state, and is called water; and when raised to the temperature of 212°, under ordinary circumstances, it passes into the aeriform state, and is called steam. It is to this last change that we wish at present principally to call the attention of the reader. In the transition of water from the liquid state to the state of vapour or steam, an immense change of bulk takes place. In this change, a solid inch of water enlarges its size about 1,700 times, and forms 1,700 solid inches of steam. This expansion takes place accompanied with a certain force or pressure, by which the vapour has a tendency to burst the bounds of any vessel which contains it. The steam which fills 1,700 solid inches at the temperature of 212°, will, if cooled below that temperature, return to the liquid form, and occupy only one solid inch, leaving 1,699 solid inches vacant; and, if it be included in a close vessel, leaving the surfaces of that vessel free from the internal pressure to which they were subject before the return of the water to the liquid form. If it be possible, therefore, alternately to convert water into vapour by heat, and to reconvert the vapour into water by cold, we shall be enabled alternately to submit any surface to a pressure equal to the elastic force of the steam, and to relieve it from that pressure, so as to permit it to move in obedience to any other force which may act upon it. Or again, suppose that we are enabled to expose one side of a movable body to the action of water converted into steam, at the moment that we relieve the other side from the like pressure by reconverting the steam which acts upon it into water, the movable body will be impelled by the unresisted pressure of the steam on one side. When it has moved a certain distance in obedience to this force, let us suppose that the effects are reversed. Let the steam which pressed it forwards be now reconverted into water, so as to have its action suspended; and at the same moment, let steam raised from water by heat be caused to act on the other side of the movable body; the consequence will obviously be, that it will now change the direction of its motion, and return in obedience to the pressure excited on the opposite side. Such is, in fact, the operation of an ordinary low-pressure steam-engine. The piston or plug which plays in the cylinder is the movable to which we have referred. The vapour of water is introduced upon one side of that piston at the moment that a similar vapour is converted into water on the other side, and the piston moves by the unresisted action of the steam. When it has arrived at the extremity of the cylinder, the steam which just urged it forwards is reconverted into water, and the piston is relieved from its action. At the same moment, a fresh supply of steam is introduced upon the other side of the piston, and its pressure causes the piston to be moved in a direction contrary to its former motion. Thus the piston is moved in the cylinder alternately in the one direction and in the other, with a force equivalent to the pressure of the steam which acts upon it. A strong metal rod proceeds from this piston, and communicates with proper machinery, by which the alternate motion of the piston backwards and forwards, or upwards and downwards, in the cylinder, may be communicated to whatever body is intended to be moved.

The power of such a machine will obviously depend partly on the magnitude of the piston or the movable surface which is exposed to the action of the steam, and partly on the pressure of the steam itself. The object of converting the steam into water by cold, upon that side of the piston towards which the motion takes place, is to relieve the piston from all resistance to the moving power. This renders it unnecessary to use steam of a very high pressure, inasmuch as it will have no resistance to overcome, except the friction of the piston with the cylinder, and the ordinary resistance of the load which it may have to move. Engines constructed upon this principle, not requiring, therefore, steam of a great pressure, have been generally called "low-pressure engines." The re-conversion of the steam into water requires a constant and abundant supply of cold water, and a fit apparatus for carrying away the water which becomes heated, by cooling the steam, and for supplying its place by a fresh quantity of cold water. It is obvious that such an apparatus is incompatible with great simplicity and lightness, nor can it be applied to cases where the engine is worked under circumstances in which a fresh supply of water cannot be had.

The re-conversion 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 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.

The steam-engine therefore consists of two distinct parts,—the boiler, which is at once the generator and magazine of steam, and the cylinder with its piston, which is the instrument by which this power is brought into operation and rendered effective. The amount of the load or resistance which such a machine is capable of moving, depends upon the intensity or pressure of the steam produced by the boiler, and on the magnitude of the surface of the piston in the cylinder, upon which that steam acts. The rate or velocity of the motion depends, not on the power or pressure of the steam, but on the rate at which the boiler is capable of generating it. Every stroke of the piston consumes a cylinder full of steam; and of course the rate of the motion depends upon the number of cylinders of steam which the boiler is capable of generating in a given time. These are two points which it is essential should be distinctly understood, in order to comprehend the relative merits of the boilers used in travelling steam-engines.

The motion which is primarily produced in a steam engine is a reciprocating or alternate motion of the piston from end to end of the cylinder; but the motion which is necessary to be produced for the purposes to which the engine is applied, is rarely or never of this nature. This primary motion, therefore, is almost always modified by some machinery interposed between the piston and the object to be moved. The motion most generally required is one of rotation, and this is accomplished by connecting the extremity of the piston-rod with a contrivance constructed on the revolving axle, called a crank. This contrivance does not differ in principle from the common winch, or from the key which winds a clock. The motion of the piston-rod backwards and forwards turns such a winch. At each termination of the stroke, the piston, from the peculiar position of the crank, loses all power over it. To remedy this two cylinders and pistons are generally used, which act upon two cranks placed on the axle at right angles to each other; so that at the moment when one of the pistons is at the extremity of its stroke, and loses its power upon one crank, the other piston is at the middle of its stroke, and in full operation on the other crank. By these means an unremitting force is kept in action.

Edinburgh Review.

SONG

BY ROBERT GILFILLAN, AUTHOR OF "ORIGINAL SONGS."

Tune.—"Gin a body meet a body."

Bonnie lassie, fairest lassie,Dear art thou to me;Let me think, my bonnie lassie,I am lov'd by thee!I speak na of thy ringlets bright,Nor of thy witching 'ee;But this I'll tell thy bonnie sel',That dear art thou to me!O! beauty it is rare, lassie,And beauty it is thine,Yet my love is no for beauty's sake,'Tis just I wish thee mine!Thy smile might match an angel's smile,Gif such, save thee, there be;Yet though thy charms my bosom warms,I'll tell na them to thee!Thy sunny face has nature's grace,Thy form is winsome fair;But when for long thou'st heard that sang,O! wherefore hear it mair?Thy voice, soft as the hymn of morn,Or evening's melodie,May still excel, as a' can tell,Then wherefore hear't frae me?Bonnie lassie, fairest lassie,Think na't strange o' me,That when thy beauty's praised by a',Thou get'st nae praise frae me?For wha wad praise what none can praise?Yet, lassie, list to me;Gie me thy love, and in returnI'll sing thy charms to thee!Metropolitan.

ANECDOTE GALLERY

RECORDS. BY THE AUTHOR OF "MONSIEUR TONSON."

An Odd Angler.

Dr. Birch was very fond of angling, and devoted much time to that amusement. In order to deceive the fish, he had a dress constructed, which, when he put it on, made him appear like an old tree. His arms he conceived would appear like branches, and the line like a long spray. In this sylvan attire he used to take root by the side of a favourite stream, and imagined that his motions might seem to the fish to be the effect of the wind.—He pursued this amusement for some years in the same habit, till he was ridiculed out of it by his friends.

Jack Spencer.

It is said that he once contrived to collect a party of hunch-backed men to dine with him, some of whom indignantly quitted the table. Another whimsical party which he assembled at his house consisted merely of a number of persons all of whom stuttered; but this meeting at first threatened serious consequences, for each supposed he was mocked by the other, and it was with great difficulty that their host restored peace, by acknowledging the ludicrous purpose of his invitation.

Dr. Johnson.

Dr. Johnson was long a bigoted Jacobite. When he was walking with some friends in Kensington Gardens, one of them observed that it was a fine place. "Phoo," said Johnson, "nothing can be fine that belongs to a usurper." Dr. Monsey assured me, that once in company, when the conversation was on the age of King George the Third, he heard him say, "What does it signify when such an animal was born, or whether he ever existed?" Yet he afterwards said, in his account of his interview with His Majesty, that it was not for him "to bandy compliments with his sovereign."

Cards.

Mr. Murphy told me also, that he was once present at Tom's Coffee-house, in Russell Street Covent Garden, which was only open to subscribers, when Colley Cibber was engaged at whist, and an old General was his partner. As the cards were dealt to him, he took up every one in turn, and expressed his disappointment at every indifferent one. In the progress of the game he did not follow suit, and his partner said, "What! have you not a spade, Mr. Cibber?" The latter, looking at his cards, answered, "Oh, yes, a thousand;" which drew a very peevish comment from the General. On which Cibber, who was shockingly addicted to swearing, replied, "Don't be angry, for – I can play ten times worse if I like."

All on one Side.

Major Grose told me that when he was quartered in Dublin, he ordered an Irish sergeant to exercise the men in shooting at a mark. The sergeant had placed a pole for them to take aim, stationing a certain number on one side, and an equal number on the other, in direct opposition. The Major happened to reach the spot just as they were going to fire, stopped them, and expressed his surprise that the sergeant should have placed them in so dangerous a position, as they must necessarily wound, if not kill each other. "Kill each other!" said the sergeant, "why, they are all our own men." As the men so contentedly remained in the dangerous position, it may be inferred that they were as wise as the sergeant. This story illustrates that of Lord Thomond's cooks, which when the keeper let loose, were fighting each other,—much to his surprise he said, as they belonged to one person, and were "all on the same side."

Vails to Servants.

It is said that this practice prevailed to such a degree, even at the house of the great Lord Chesterfield, that when he invited Voltaire a second time to his table, the French wit in his answer declined the invitation, alleging that "his lordship's ordinary was too dear."

Another evil practice of servants to the higher orders, at that time, was carried to such a height that it wrought its own cure. It was usual at the old Italian Opera-house to allot a gallery to the footmen, that when their masters or mistresses had appointed the time to leave the theatre, their servants might be ready to attend. But these livery-men took it into their heads to become critics upon the performances, and delivered their comments in so tumultuous a manner, that the managers found it absolutely necessary to close the gallery against them, and to assign it to those only who paid for admission.

Just before the abolition of this party-coloured tribunal, a wag who was fond of music, but who had more wit than money, appeared at the gallery door, when the porter demanded the name of his master. The wag boldly answered, "I am the Lord Jehovah's servant," and was admitted, one of the door-keepers saying to the other, "I never heard of that man's master before, but suppose it is some scurvy Scotch lord or other."

New Reading.

Mr. John Kemble used to relate many whimsical anecdotes of provincial actors whom he knew in the early part of his life. He said that an actor who was to perform the character of Kent in the play of "King Lear," had dressed himself like a doctor, with a large grizzle wig, having a walking-stick, which he held up to his nose, and a box under his arm. Being asked why he dressed the Earl of Kent in that manner, he said, "People mistake the character; he was not an earl, but a doctor. Does not Kent say, when the king draws his sword on him for speaking in favour of Cordelia, 'Do kill thy physician, Lear;' and when the king tells him to take his 'hated trunk from his dominions,' and Kent says, 'Now to new climes my old trunk I'll bear,' what could he mean but his medicine chest, to practise in another country?"

Absence.

The first Lord Lyttleton was very absent in company, and when he fell into a river, by the oversetting of a boat, at Hagley, it was said of him that he had "sunk twice before he recollected he could swim." Mr. Jerningham told me, that dining one day with his lordship, the earl pointed to a particular dish, and asked to be helped of it, calling it, however, by a name very different from what the dish contained. A gentleman was going to tell him of his mistake. "Never mind," whispered another of the party; "help him to what he asked for, and he will suppose it is what he wanted."

Arthur Murphy, whose mind was chiefly occupied by dramatic subjects, after he became a barrister, dining one Sunday at the chaplain's table, St. James's Palace, being too early, strolled into the Chapel Royal during the service, and desiring a seat, he thus addressed one of the attendants on the pews, "Here, boxkeeper, open this box."

MANNERS AND CUSTOMS

CURIOUS LAWS RELATING TO CAPS

In England, in the year 1571, it was enacted, "that every person above seven years of age should wear on Sundays and holidays a cap of wool, knit-made, thickened and dressed in England, by some of the trade of cappers, under the forfeiture of three farthings for every day's neglect, excepting maids, ladies, and gentlewomen, and every lord knight, and gentleman, of twenty marks of land, and their heirs, and such as have borne office of worship in any city, town, or place, and the wardens of the London Companies."

In France, those who had been bankrupts were obliged ever after to wear a green cap, to prevent people from being imposed on in any future commerce. By several arrets, in 1584, 1622, 1628, and 1688, it was decreed, that if they were at any time found without their green cap, their protection should be null, and their creditors empowered to cast them into prison; but this practice is not now continued.

Among the formation of the different domestic trades of the metropolis into fraternities, or companies, were the Capellarii, or Cappers. Respecting these, Hugh Fitz-Otonis, the city custos, in the 54th of Henry III., made certain ordinances, in the presence of the aldermen, as that none "should make a cap but of good white or grey wool, or black; that none dye a cap made of white or grey wool into black, they being apt, so dyed, to lose their colour through the rain," &c.

P.T.W.

WRESTLING

At Hornchurch, in Essex, there is a singular custom on Christmas Day of wrestling for a boar's head, which is provided by the occupier of Hornchurch Hall. This custom is said to have originated in some charter, with which a correspondent, (H.B.A.,) is totally unacquainted.

PERSECUTION OF THE JEWS

Mr. Turner has collected (Hist. Eng.) many curious facts relative to the condition of the Jews, especially in England. Others may be found dispersed in Velly's History of France; and many in the Spanish writers, Mariana and Zurita. The following are from Vaissette's History of Languedoc:—It was the custom at Toulouse to give a blow on the face to a Jew every Easter;—this was commuted, in the twelfth century, for a tribute. At Beziers another usage prevailed—that of attacking the Jews' houses with stones, from Palm Sunday to Easter. No other weapon was to be used; but it generally produced bloodshed. The populace were regularly instigated to the assault by a sermon from the bishop. At length, a prelate, wiser than the rest, abolished this ancient practice, but not without receiving a good sum from the Jews.

THE GATHERER

Crusades.—Mr. Hallam, in his excellent History of the Middle Ages, (vol. iii. p. 359), gives the following view of these misconceived glories of history:—"The crusades may be considered as martial pilgrimages on an enormous scale; and their influence upon general morality seems to have been altogether pernicious. Those who served under the cross would not indeed have lived very virtuously at home; but the confidence in their own merits, which the principle of such expeditions inspired, must have aggravated the ferocity and dissoluteness of their ancient habits. Several historians attest the depravation of morals which existed both among the crusaders, and in the states formed out of their conquests."

Slave Trade in England.—In England it was very common, even after the conquest, to export slaves to Ireland; till, in the reign of Henry II., the Irish came to a non-importation agreement, which put a stop to the practice. William of Malmesbury accuses the Anglo-Saxon nobility of selling their female servants as slaves to foreigners. In the canons of a council at London, in 1102, we read—"Let no one from henceforth presume to carry on that wicked traffic, by which men of England have hitherto been sold like brute animals." And Giraldus Cambrensis says that the English, before the conquest, were generally in the habit of selling their children and other relations, to be slaves in Ireland, without having even the pretext of distress or famine, till the Irish, in a national synod, agreed to emancipate all the English slaves in the kingdom.

Opulent English Merchants.—Some idea of the ancient commercial wealth of Great Britain may be gathered from a glance at the rapid increase of English trade from about the middle of the fourteenth century. Thus, in 1363, Ricard, who had been lord mayor, some years before, entertained Edward III. and the Black Prince, the Kings of France, Scotland, and Cyprus, with many of the nobility, at his own house in the Vintry, and presented them with handsome gifts. This eclipses the costliest entertainments of our times, at the public expense. Philpot, another eminent citizen in Richard II.'s time, when the trade of England was considerably annoyed by privateers, hired one thousand armed men, and dispatched them to sea, where they took fifteen Spanish vessels with their prizes. We find Richard obtaining a great deal from private merchants and trading towns. In 1379, he got 5,000l. from London, 1,000 marks from Bristol, and in proportion from smaller places. In 1386 London gave 4,000l. more, and 10,000 marks in 1397. The latter sum was obtained also for the coronation of Henry VI. Nor were the contributions of individuals contemptible, considering the high value of money. Hinde, a citizen of London, lent to Henry IV. 2,000l. in 1407, and Whittington one half of that sum. The merchants of the staple advanced 4,000l. at the same time. Our commerce continued to be regularly and rapidly progressive during the fifteenth century. The famous Canynges, of Bristol, under Henry VI. and Edward IV. had ships of 900 tons burden.

Gold-beating.—Reaumur asserts, that in an experiment he made, one grain of gold was extended to rather more than forty-two square inches of leaf-gold; and that an ounce of gold, which in the form of a cube, is not half an inch either high, broad, or long, is beat under the hammer into a surface of 150 square feet. The process is as follows:—The gold is melted in a crucible, and taken to the flattening mills, where it is rolled out till it becomes of the consistence of tin; it is then cut into small square pieces, and each piece is laid between a leaf of skin (known by the name of goldbeaters-skin); two parchment bands are then passed over the whole, and each band is reversed; it is then hammered out to the size of the skin, taken out, cut and hammered over again, and so on till it is sufficiently thin; when it is placed in books, the leaves of which are rubbed with red ochre, to prevent the gold adhering to them. There are gold leaves not thicker, in some parts, than the three hundred and sixty thousandth part of an inch. BURTON.