LESSONS IN READING AND ELOCUTION. No. XI. ANALYSIS OF THE VOICE. EXERCISES ON INFLECTIONS. RISING INFLECTION.-RULE I. 'High Rising Inflection.' 1. "Ha! say you só?” 2." What!-confer a crown on the author of the public calamities?" 3. "Indeed!-acknowledge a traitor for our sovereign?" RULE II. Moderate Rising Inflection.'-Exercise 1. "In every station which Washington was called to fill, he acquitted himself with honour." 2. "As the evening was now far advanced, the party broke up." 3. "Where your tréasure is, there will your heart be also." 4. "Though we cannot discern the reasons which regulate the occurrence of events, we may rest assured that nothing can happen without the cognisance of Infinite Wisdom." 5. "Despairing of any way of escape from the perils which surrounded him, he abandoned his struggles, and gave himself up to what seemed his inevitable doom.' 6. "Had I suffered such enormities to pass unpunished, I should have deemed myself recreant to every principle of justice and of duty." Note and Exception. Words and phrases of address.'Exercise. "Listen, Amèricans, to the lesson which seems borne to us on the very air we breathe, while we perform these dutiful rights. Ye winds, that wafted the pilgrims to the land of promise, fan, in their children's hearts, the love of freedom! Blood which our fathers shed, cry from the ground;-echoing arches of this renowned hall, whisper back the voices of other days; glorious Washington! break the long silence of that votive canvass ;-speak, speak, marble lips; teach us THE LOVE OF LIBERTY PROTECTED BY LAW!" 2. "Your steps were hasty ;-did you speed for nothing? Your breath is scanty;-was it spent for nothing? Your looks imply concern ;-concern for nothing?" Exception. Emphasis.'-Exercise 1. "Tell me not of the honour of belonging to a free country.-I ask, does our liberty bear generous fruits?" 2. Was there a village or a hamlet on Massachusetts Bay, which did not gather its hardy seamen to man the gun-decks of your ships of war? Did they not rally to the battle, as men flock to a feast ?" 3. Is there a man among you, so lost to his dignity and his duty, as to withhold his aid at a moment like this ?" RULE V. Penultimate Inflection.'-Exercise 1. "All is doubt, distrúst, and disgrace; and, in this instance, rely on it, that the certain and fatal result will be to make Ireland hate the connexion, contemn the councils of England and de-pise her power.' 2. "I am at a loss to reconcile the conduct of men, who, at this moment, rise up as champions of the East India Company's charter; although the incompetence of that company to an adequate discharge of the trust deposited in them, are themes of ridicule and contempt to all the world; and, although, in consequence of their mismanagement, connivance, and imbecility, combined with the wickedness of their servants, the very name of an Englishman is detested, even to a proverb, through all A'sia; and the national character is become disgraced and dishonoured." 3. "It will be the duty of the historian and the sage, in all ages, to omit no occasion of commemorating that illustrious man; and, till time shall be no more, will a test of the progress which our race made in wisdom and in virtue, be derived from the veneration paid to the immortal name of Washington." Exception. Emphasis.'-Exercise 1. "Let us bless and hallow our dwellings as the homes of freedom. Let us make them, too, the homes of a nobler freedom,-of freedom from vice, from evil pàssion,-from every corrupting bondage of the soul !" 2. "If guilty, let us calmly abide the results, and peaceably submit to our sentence; but if we are traduced, and really RULE III. Note.-'Poetic Series.'-Example 1. "Power, be innocent, tell ministers the truth,-tell them they are will, sensation, mémory, failed in turn." 2 "Oh! the dread mingling, in that awful hour, Of all terrific sounds!-the savage tone tyrants; and strain every effort to avert their oppression.' 3. "Heaven has imprinted in the mother's face something beyond this world, something which claims kindred with the skies, the angelic smile, the tender look, the waking, watchful eye, which keeps its fond vigil over her slumbering babe. -In the heart of man lies this lovely picture; it lives in his sympathies; it reigns in his affèctions; his eye looks round, in vain, for such another object on earth." FALLING INFLECTION. RULE I. 'Intensive Downward Slide.' 2. "MACGREGOR! MACGREGOR!' he bitterly cried." 4. "To ARMS! gallent Frenchmen, to A'RMS!" 5. "Oh! SHAME on us, countrymen, shame on us ALL! If we cringe to so dastard a race!" 6. "TREMBLE, ye traitors! whose schemes TREMBLE! for, roused from your parricide dreams, 4. "Onward still the remote Pawnee and Mandan will beckon, whither the deer are flying, and the wild horse roams, where the buffalo ranges, and the condor soars, - far towards the waves where the stars plunge at midnight, and amid which bloom those ideal scenes for the persecuted savage, where sentence. Exercise 1. white men will murder no more for gold, the game upon the sunshine hills." # nor startled RULE IV. Questions which may be answered by Yes or No.-Exercise 1. "Has not the patronage of peers incréased? Is not the patronage of India now vested in the crown? Are all these innovations to be made to increase the influence of the exécutive power; and is nothing to be done in favour of the pópular part of the constitution, to act as a counterpoise?" The penultimate inflection of a concluding series, or of a clause that forms perfect sense, is the same in kind with that which precedes a period, except in verse and poetic prose, which, in long passages of great beauty, retain the suspensive slide. RULE II. 'Full' Falling Inflection, in the cadence of a "The changes of the year impart a colour and character to our thoughts and feelings." 2. "To a lover of nature and of wisdom, the vicissitude of seasons conveys a proof and exhibition of the wise and benevolent contrivance of the Author of all things."" 3. "He who can approach the cradle of sleeping innocence without thinking that of such is the kingdom of heaven,' or see the fond parent hang over its beauties, and half retain her breath, lest she should break its slumbers, without a veneration beyond all common feeling,-is to be avoided in every intercourse of life, and is fit only for the shadow of darkness, and the solitude of the desert." See foot-note preceding column. Exception. Modified Cadence.'-Exercise 1. "This monument is a plain shaft. It bears no inscription, fronting the rising sun, from which the future antiquarian shall wipe the dúst. Nor does the rising sun cause tones of music to issue from its súmmit. But at the rising of the sun, and at the setting of the sun, in the blaze of noon-day, and beneath the milder effulgence of lunar light, it speaks, it acts, to the full comprehension of every British mind, and the awakening of glowing enthusiasm in every British heart." 2. "I speak not to you, sir, of your own outcast condition. -You perhaps delight in the perils of martyrdom. I speak not to those around me, who, in their persons, their substance, and their families, have endured the torture, poverty, and irremediable dishonour. They may be meek and hallowed men,-willing to endure." 3. "The foundation on which you have built your hopes, may seem to you deep and firm. But the swelling flood, and the howling blast, and the beating rain, will prove it to be but treacherous sand." RULE III. 'Moderate' Falling Inflection, of complete sense.Exercise 1. "Animal existence is made up of action and slumber: nature has provided a season for each." 2. "Two points are manifest: first, that the animal frame requires sleep; secondly, that night brings with it a silence, and a cessation of activity, which allow of sleep being taken without interruption, and without loss." 3. "Joy is too brilliant a thing to be confined within our own bosoms: it burnishes all nature, and, with its vivid colouring, gives a kind of factitious life to objects without sense or motion." 4. "When men are wanting, we address the ànimal creation; and, rather than have none to partake our feelings, we find sentiment in the music of birds, the hum of insects, and the lowing of kine; nay, we call on rocks and streams and forests to witness and share our emotions." 5. "I have done my duty:-I stand acquitted to my conscience and my country: -I have opposed this measure throughout; and I now protest against it, as harsh, upprèssive, un àlled for, unjust, -as establishing an infamous precedent, by retaliating crime against crime,-as tyrannous,cruelly and vindictively tyrannous." Exception. Plaintive Expression.' Exercise 1. "I see the cloud and the tempest near, The voice of the troubled tide I hear; The torrent of sorrow, the sea of grief, 2. "No deep-mouthed hound the hunter's haunt betrayed, No lights upon the shore or waters played, No loud laugh broke upon the silent air, To tell the wanderers man was nestling there." 3. "The dead leaves strew the forest walk, And Autumn, with her yellow hours, · RULE IV. and Note 1. Simple Commencing Series.' Exercise 1. "The old and the young are alike exposed to the shafts of Death." 2. "The healthy, the temperate, and the virtuous, enjoy the true relish of pleasure." 3. "Birth, rank, wealth, learning, are advantages of slight value, if unaccompanied by personal worth." 4. "Gentleness, patience, kindness, candour, and courtesy, form the elements of every truly amiable character." 5. "Sympathy, disinterestedness, magnanimity, generosity, liberality, and self-forgétfulness, are qualities which universally secure the esteem and admiration of mankind." Compound Commencing Series. Exercise 1. "In a rich soil, and under a soft climate, the weeds of luxury will spring up amid the flowers of art." 2. "All the wise institutions of the lawgiver, all the doctrines of the sage, all the ennobling strains of the poet, had perished in the ear, like a dream related, if letters had not preserved them." 8. "The dimensions and distances of the planets, the causes of their revolutions, the path of comets, and the ebbing and flowing of tides, are now understood and explained." 4. "The mighty pyramid, half buried in the sands of Africa, has nothing to bring down and report to us, but the power of kings, and the servitude of the people. If asked for its moral object, its admonition, its sentiment, its instruction to mankind, or any high end in its erection, it is silent ;-silent as the millions which lie in the dust at its base, and in the caracombs which surround it." 5. "Yes, let me he frèe; let me go and come at my own will; let me do business, and make journeys, without a vexatious police or insolent soldiery to watch ny stèps; let me think, and do, and speak, what I please, subject to no limit but that which is set by the common wèal; subject to no law but that which conscience binds upon me; and I will bless my country, and love its most rugged rocks, and its most barren soil." Exception 3. Poetic and Pathetic Series.' God is ever near at hand, Golden shield from danger." 2. "Rocks of granite, gates of brass, Bow, to let the wishes pass 3. "From the phantoms of the night, Thoughts which rack the slumbering breast, Hide us 'neath Thy mercy's shade." 4. "From the stars of heaven, and the flowers of earth, From all save that o'er which soul bears sway, 4. "What is human life, but a waking dream,-a long reverie,-in which we walk as in a vain show, and disquiet ourselves for naught?' In childhood we are surrounded by a dim, unconscious present, in which all palpable realities seem for ever to elude our grasp; in youth, we are but gazing into the far future of that life for which we are consciously pre-being, like enumeration, cumulative in effect, and corresponding, ward paring; in manhood, we are lost in ceaseless activity and enterprise, and already looking forward to a season of quiet and repose, in which we are to find ourselves, and listen to a voice within; and in old age, we are dwelling on the shadows of the past, and gilding them with the evanescent glow which emanates from the setting sun of life." Falling slide of contrast to the preceding clause. All emphatic series, even in suppositive and conditional expression, fore, to climax in style, are properly read with a prevailing downward slide in the suspensive' or slight form, which bel nas to incomplete but energetic expression, and avoids, accordingly, the low inflection of cadence at a period. slide for the slight suspensive one. But the tone, in such cases, will stil Emphasis, and length of clause, may substitute the moderate' falling be perfect y tree from the descent of a cadence, which belongs only to the The inflection of any clause always lies on the emphatic word; and, if that word is a polysyllable, on the accented syllable chiefly, although not always exclusively period. 5. "When the summer exhibits the whole force of active nature, and shines in full beauty and splendour; when the succeeding season offers its 'purple stores and golden grain,' or displays its blended and softened tints; when the winter puts on its sullen aspect, and brings stillness and repose, affording a respite from the labours which have occupied the preceding months, inviting us to reflection, and compensating for the want of attractions abroad, by fireside delights and home-felt jóys; in all this interchange and variety, we find reason to acknowledge the wise and benevolent care of the God of seasons." HISTORICAL MS. MAGAZINE. SIR, I was very much pleased with the letter of "T. J." published in No. 105 of the P. E., and think his plans excellent. This note suggested to me the idea of starting a manuscript Magazine on the subject of HISTORY, commencing with the history of our own dear isle. Perhaps, sir, you will be so obliging as to publish this letter in the P. E., as I wish it to meet the eyes of several young persons who are desirous of studying the science of history zine is requested to communicate with the editor by letter, directed, in the manner proposed. Any person wishing to join this magaSigma, Post-office, 103, Tottenham-court-road, London." Before I conclude, I must thank you for your generous and disinterested labours for the education of your countrymen; and wishing you everv success I remain your constant reader, Σίγμα. SELF-EDUCATION. SIR,-Fourteen months ago a friend placed in my hands a num 6. "In that solemn hour, when exhausted nature can no longer sustain itself, when the light of the eye is waxing dim, when the pulse of life is becoming low and faint, when the breath labours, and the tongue falters, when the shadow of death is falling on all outward things, and darkness is beginning to gather over the faces of the loved ones who are weep-ber of the P. E. I had a great desire to improve myself, so I ing by his bedside, a ray of immortal Hope is beaming from his features: it is a Christian who is expiring." Note 2.-Exercise 1. Repeated and Heightening Rising Inflection. "I ask, will you in silence permit this invasion of your rights, at once wanton, mischievous, uncalled for, and unnecessary? Will you patiently tolerate the annihilation of all freedom,-the appointment of a supreme dictátor, who may, at his will, suspend all your rights, liberties, and privileges Will you, without a murmur of dissent, submit to a tyranny which nearly equals that of the Russian autocrat, and is second to that of Bonaparte?" 6 2. Repeated and increasing Falling Inflection.' † "Was it the winter's storm, beating upon the houseless heads of women and children; was it hard labour and spare mèals ;was it disease, was it the tomahawk; was it the deep inalady of a blighted hope, a ruined enterprise, and a broken heart;was it some, or all of these united, that hurried this forsaken company to their melancholy fate?" 3. "Yes, after he has destroyed my belief in the superintending providence of God,-after he has taught me that the prospect of an hereafter is but the baseless fabric of a vision, -after he has bred and nourished in me a contempt for that sacred volume which alone throws light over this benighted world, after having argued me out of my faith by his sophistries, or laughed me out of it by his ridicule, after having thus wrung from my soul every drop of consolation, and dried up my very spirit within me ;-yes, after having accomplished this in the season of my health and my prosperity, the sceptic would come to me while I mourn, and treat me like a drivelling idiot, whom he may sport with, because he has ruined me, and to whom, in the plenitude of his compassion,-too late, and too unavailing, he may talk of truths in which he himself does not believe, and which he has long exhorted me, and has at last persuaded me, to cast away as the dreams and delusions of human folly." CORRESPONDENCE. THE "WORKING MAN'S FRIEND" AND P. E. SIR-I have, until this day, been deprived of the advantage of possessing your valuable "EDUCATOR," but having now procured the four volumes already published, and cursorily inspected them, I cannot refrain from expressing my delight and astonishment at the valuable and extensive information therein contained. Doubtless you have experienced the loss of a "friend," and can therefore imagine with what regret I parted from my late companion and "instructor" ("The Working Man's Friend"), than which a more useful work for the operative classes never appeared. I I was promised a valuable substitute in the "P. E.," and doubt not that my disappointment at losing my old "Friend" will be amply compensated by cultivating the acquaintance of the new. With sincere repect, I am, sir, yours respectfully, Tenterden, April 27th, 1854. HENRY DRIVER. bought all the back numbers; and I have since continued to take in the monthly parts regularly. I first began my studies with Dr. Bell's Lessons in Phonetic Short-hand. I feel satisfied with the Beard's Lessons in English, the Lessons in Arithmetic, and Mr. progress I have made; but I have no person to guide or instruct me in my endeavours to improve myself. I am a married man, 29 years of age, and a policeman on a railway; part of my time is spent on night duty, and it is when I have been walking to and fro on my dreary post, that I have committed to memory the principal portion of Dr. Beard's Greek and Latin stems. I feel anxious to commence the study of the Latin Lessons; but, before doing so, I wish to have your opinion of my hand-writing and the composition of this letter. I know my hand-writing is capable of improvement; but since I have taken in the P. E. it is improved very much, from practice in writing out the exercises. Lessons; but do you not think it will be sufficient if I go through I can hardly yet venture to discharge myself from the English them again with the Latin Lessons? I can write Mr. Bell's system of short-hand, and can read it afterwards; and I hope soon to be able to report a sermon, when I go to a place of worship, which I don't do very often, as I only get one half Sunday in four, having to be on duty all the rest of the time. If Mr. Bell has published his sys'em, or vocabulary of reporting logograms, I should like to procure them. With grateful thanks for the benefit I have received from the P. E., I remain your obedient servant, G. C. (Leamington.) [In answer to this interesting letter, an example to many, we say that his hand-writing does him great credit, although capable of improvement; that it will be sufficient to go through the English Mr. Bell's Phonetic Short-hand is truly praiseworthy; and that Mr. Lessons again along with the Latin; that his perseverance with Bell has not yet published his Vocabulary of Logograms.] ANSWERS TO CORRESPONDENTS. E. J. BREMNER (Carlisle): Received the solution of 50 of the Centenary of Problems; very well done.-ANGLO-SAXON (Longport): Thanks for his broad hints.-DUTCHMAN: We should be glad to oblige him.-B. ß. (Dublin): Certainly.-Q. PRINGLE (Glasgow): Received.-J. STEELE (Manchester): We don't know any good Italian grammar. We believe that the ancient Greek would be some help to the modern, but how much we can't say. A modern Greek Testament can be had of the British and Foreign Bible Society; and by inquiry there, information may be had about modern Greek grammar.-T. W. (Leeds): The French Dictionary is com pleted; see our Literary Notices. J. G. F. R.: The map of European Russia was published in No. 102. A books, we know it not; and we would scarcely recommend to his trial the to curing bad spelling in any other way than by consulting a dictionary or printer's advice to his devil, viz. to boil a small copy of Johnson's Dictionary in milk, and eat it over night for his supper, in the hope that he would be able to spell next morning. made.-M. J. DE COGAN (Liverpool): Inquire no more about the party. W. S. Three per Cent. Stock means property in the public funds which yields 3 per cent. per annum to its possessor.-W. H. T. (Hackney): The Lessons on Phonetic Short-hand began in No. 40.-J. DOWELL (Birmingham): The spire question might be answered if the data were more complete; the nature of the cavity s not stated, whether it is also pyramidal or otherwise.-H. R. (Jewin-crescent) will be kept in view.-J. AILD (Macclesfield): We really cannot tell.-POOR SCHOLAR (Glasgow): See vol iv. p. 375 col. 2, line 27.-J. F. R. SMITH: 1. No. 2. No. 3. If a degree can be bought at any of the German universities, the more's the shame. 4. See p. 163, vol. li.-TAU (York) asks too much; he may answer all his questions himself by studying our Lessons in Geometry in the P. E., and Cassell's Eucli.-JOHN THOM, Secretary to the "Cassell's Popular Discussion Class" (but where he does not say), is informed, in answer to the question brought before the class, that, in the opinion of the Editor, if any one desirous of becoming a civil engineer or a chemist, we would recommend ་ "You waste your precious hours of time, Whilst you o'erlook your purse, your health, W., is of very litte moment.-S. A. G. (Bishop's Stortford): We may point out a few errors in his poetry-wiled for whiled; gems for flowers; and sunshining for heaven's bliss. We have heard a proverb to the effect indicated by the latter phraseology, but we thought it sounded profane.-T. C. and J. C. (Bedford): If Cleworth be the same as the Welsh Glewarth, it means a bold bear. If Cripps was originally applied to a curley-headed person, it may have come from Crisp; and if to a cunning hidden character, from Crypt. Johnson says that Gar, in Saxon, means a Weapon; of course Garside is Weaponside, or the man ready to fight with his weapon by his side.J. G. (Manchester) should consult Hutton's Mensuration, where the different forms of casks are explained; and there are practical books on gauging. EAST LOTHIAN PLOUGHMAN: The Latin poem received.-A. DONALD R. (Woolwich): The higher powers of a number are readily obtained without all the intermediate ones, by multiplying some of the earlier powers by each other. Thus, to find the 31st power of 2, or any other number; find first the cube; multiply this cube by itself, and it gives the 6th power; this multiplied by itself gives the 12th power; this again multiplied by itself gives the 24th power; this multiplied by the 6th power gives the 30th power; and this multiplied by the root gives the 31st power.-DICK (Pembroke): To inscribe a square in a semicircle, draw a straight line equal to the diameter perpendicular to one of its extremities; and join the remote extremity of this perpendicular to the centre by a straight line, and from the point where this straight line cuts the circumference, draw a perpendicular to the diameter, and it will be the side of the square required. LABORE VINCO: His solutions are correct.-AGRICOLA (Newark) will see by our solution of the Four-Ball Question, that his own is different and his answer not the same.-J. K. (Belfast): No. 101 P. E. is not out of print, and may be had on proper application to our agents-AUTODIDACTOS (Knottingley proposes the following ancient question to some of our students, after having solved it himself: "When first the marriage knot was tied, Between my wife and me, My age to hers was just allied As three times three to three; But after ten and half ten years We man and wife had been, Her age to mine was, it appears, As eight is to sixteen. Now can you, learned students, say ERRATA. DAVID: Vol ii. p. 327, col. 2, line 10, for D E read D F. J. Wardle (Dean Mill): Vol. Iv. p. 329, line 32 from top, for the whole read one-half of the whole. LITERARY NOTICES. CASSELL'S EDUCATIONAL WORKS. CASSELL'S FRENCH DICTIONARY In Two Parts:-1. French and English; 2. English and French. The English Department by Professor WALLACE and H. BRIDGEMAN, Esq. In French Department carefully edited by Professor DE LOLME, and the one large handsome Octavo Volume, price 9s. 6d. strongly bound. 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This work is intended to supply the people with such information relating to the study of the Bible as the POPULAR EDUCATOR has given in reference to Secular Instruction. It contains a Literary History of the Sacred Books -Accounts of their Original Text-Canonical Authority, and most Ancient Versions-The Principle and Laws of Interpretations, and the Methods of Discovering the Literal or Symbolical Meaning of Inspired WritingsIllustrations of the Geography and Natural History of Palestine-The Manners and Customs, the Laws and Worship of its People-The Antiquities of the Four Great Monarchies-The Fulfilment of Prophecy concerning them and other ancient nations-and the Fruits of modern Travel and Discovery in the East, etc. The work is written in a popular style, and is therefore specially adapted to supply Families, Sunday-school Teachers, and others. with that amount of information respecting the Holy Bible which they need in order to meet the charges of Infidels and the subtleties of Romanists, and to confirm and establish their own minds in the genuineness and authenticity of Holy Writ. Wherever the subject requires Pictorial Illustrations they are introduced. ON PHYSICS, OR NATURAL PHILOSOPHY. No. XXXVI. (Continued from page 129.) Vapours.-Aeriform fluids which arise from liquids by the absorption of caloric are called vapours; such as those produced from ether, alcohol, water, and mercury. Those liquids which possess the power of passing into the aeriform state are called volatile; and those which give out no vapour at any temperature are called fixed, as the fat oils. There are some solids, as ice, arsenic, camphor, and generally odorific substances, which give out vapours at once without passing through the liquid state. Vapours, like gases, are usually transparent and colourless; there are only a few coloured liquids whose vapours are also coloured. Vaporisation. The passage of a body from the liquid to the vaporous state is known under the general name of vaporisation; but by this term is particularly understood the slow production of vapour at the surface of a liquid; and by ebullition, a rapid production of vapour in the mass itself. The latter is produced, under the ordinary pressure of the atmosphere, in the same manner as fusion, at a determinate temperature for each liquid. In the case of evaporation, the effects are different; for this process goes on at various temperatures in the same liquid. Yet beyond a certain point of refrigeration, all vaporisation appears to cease. Mercury, for example, gives out no vapour below -10° Centigrade; and sulphuric acid none below 30° Centigrade. Elastic Force of Vapours.-Like gases, vapours have an elastic force, in consequence of which they act with a certain degree of pressure on the sides of the vessels which contain them. To prove the tension of vapours, and at the same time to render them sensible to the eye, a glass tube of siphon shape inverted is half filled with mercury, fig. 186, then a drop of C Fig. 186. Formation of Vapour's in a Vacuum.-In the preceding experiment, the passage of the liquid into the state of vapour takes place slowly. The same thing happens also when a volatile liquid is freely exposed to the air. In both cases the atmospheric pressure is an obstacle to the vaporisation; but it is no longer so when the liquids are placed in a vacuum. The elastic force of vapours then meeting with no resistance, their formation is instantaneous. To show this, several barometric tubes are placed in the same cistern, fig. 187. These tubes being filled with mercury, one of them, the tube A for instance, is employed as a barometer; then drops of water, alcohol, and ether, are introduced into the tubes B, D, and E respectively. It is observed that at the moment when the liquid enters the barometric vacuum in each of the tubes, the level of the mercury sinks, as shown in the figure. Now, it is not the weight of the liquid introduced which depresses the mercury; for this weight is only a very small fraction of that of the mercury displaced. There is therefore, in the case of each liquid, an instantaneous production of vapour, of which the elastic force acts upon the mercurial column. From this experiment it is also evident that the depression of the mercury is not the same in the three tubes; it is greater in the tube where the alcohol is, than in that where the water is; and greater in the tube where the ether is, than in either of the other two. We are thus enabled to state the following laws on the formation of vapours: 1st. In a vacuum, all volatile liquids vaporise instantaneously. 2nd. At the same temperature, the vapours of different liquids do not possess the same elastic force. As an example of the second law, the tension of the vapour of ether is nearly twenty-three times greater than that of the vapour of water. ether is passed into the shorter branch, which is closed, and Maximum of Tension.-When a very small quantity of a the tube is then immersed in a water-bath about 45° Centi- volatile liquid, such as ether, is introduced into a barometric grade. The mercury will now sink in the smaller branch, the tube, it vaporises instantaneously and completely, and the space AB will be filled with a gas having entirely the appear- column of mercury does not experience all the depression of ance of air, and whose elastic force evidently balances the which it is capable; for if another small quantity of ether be weight of the column of mercury c D, as well as the pressure introduced, the depression will increase. By continuing this of the atmosphere which acts on D; this gas is the vapour of operation, a moment will at last arrive when the ether introether. If we cool the water in the vessel, or if we withdraw duced into the tube will cease to vaporise and will remain the tube from it, which will produce the same effect, the in the liquid state. There is therefore, for a given temperavapour which filled the space A B will rapidly disappear, and ture, a limit to the quantity of vapour which can be formed the drop of ether will reappear. If, on the contrary, the water-in a given space. In this case, the given space is said to be bath be heated more and more, the level of the mercury will saturated. Moreover, at the instant when the vaporisation of ink below the point B, and thus the tension will be increased. the ether ceases, the depression of the mercury ceases. There VOL. V. 114 |