Читать книгу: «The Mirror of Literature, Amusement, and Instruction. Volume 20, No. 575, November 10, 1832», страница 5
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 return
I'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."
