LESSONS IN FRENCH. neighbourhood a fame and splendour which had never been equalled. The Spartans had united to repel the common invader, and were content for some time afterwards to share in the commonwealth under the government at Athens. But the prosperity and power which gradually arose rankled in the Spartan breasts, and ended in a rebellion. The Spartans, jealous of their rivals' power, secretly prepared to undermine it. Pericles was the chief minister at Athens; and under his brilliant administration it rose to the summit of its greatness. He adorned the city with the most choice paintings and sculpture, and encouraged art of every description. But in his time the jealousy of Sparta assumed a substantial form; and the Peloponnesian war (B.C. 431-404) commenced. Athens attacked the Peloponnesus by sea, while the Spartans invaded Attica by land. This war led to the supremacy of Sparta; and from this time we may date the commencement of the downfall of Greece. The disturbances occasioned by the Peloponnesian war did not for some time interfere with the progress of Greece in culture and art; but the period had now arrived when it was shortly to lose altogether its freedom, and, with the loss of its freedom, to cease to advance in civilisation. The kingdom of Macedon, of which Philip was ruler, was situated in the north of Greece. The dissensions which existed amongst the Greeks induced him to turn his thoughts to the conquest of Greece. One battle at Chæronea gave him its command. In vain did the country try afterwards to free itself from the yoke. It had irrevocably lost the power. True, the Romans relieved Greece of the tyranny of Macedonia at a later period, but only to make both subject to the power of the Roman empire; and the capture of Corinth, about 146 years before Christ, finally placed Greece in the hands of Rome. It would be useless to pursue the history of ancient Greece any further. Its rise and its power have been shown; it owed both to independence. With the loss of this it lost all that is absorbing or great in its history. We see in the ancient history of Greece the forecast of many events of modern history. That events do reproduce themselves in the most remarkable way is undoubted, and that history repeats itself constantly is certain. In the history of ancient Greece we see the same strife, the same endeavours, the same power, and the same prosperity, coming from free government and energetic life, as we LOW may see in the present day in our own country or on the other side of the Atlantic. And if its history gives us lessons to follow, it also affords many warnings of dangers which no free state can afford to disregard. 285 (3.) The pronouns qui, que, lequel, dont, and the word où, meaning in which, should be followed by the subjunctive when that part of the sentence which precedes them expresses an interrogation, or implies a wish, a doubt, or a condition. They must also be followed by the verb in the subjunctive when they are preceded by a superlative relative [§ 14 (9)]: La meilleure chose que vous puis- The best thing that you can do. siez faire, (4.) A verb preceded by que and one of the unipersonal verbs falloir, importer, convenir, suffire, valoir mieux, or by the verb être, used unipersonally in connection with the adverbs fâcheux, juste, injuste, surprenant, possible, or with à propos, temps, à désirer, à souhaiter, etc., must be put in the subjunctive [see Sect. LXXII., R. 1]: (4.) We might give as a general rule, that a verb immediately preceded and governed by another verb (avoir and être excepted), or by a preposition (en excepted), is put in the present of the infinitive: Tout ce qu'elle s'imaginait tenir, lui échappait tout-à-coup, All that she fancied that she held escaped her suddenly. (5.) The French language, preferring the active to the passive voice, requires the use of the active verb in the following and similar cases wherein the English use the passive voice : Cette dame est bien à plaindre, Cette maison est à vendre, That lady is much to be pitied. This house is to be sold. §129.-GOVERNMENT OF VERBS. Some verbs are in English governed by prepositions different from those which connect or govern the same verbs in French. Some, again, which are in English joined by prepositions, require none between them in French. We give below lists of verbs with the appropriate prepositions, according to the best French authorities. § 130.-VERBS REQUIRING NO PREPOSITION BEFORE ANOTHER VERB IN THE INFINITIVE. Accourir. Aimer mieux. Retourner. Revenir. Aller. Apercevoir. I fear, I tremble, I apprehend, I am afraid he may come. Assurer. * When two verbs are united by the conjunction que, the second is put in the indicative if the first expresses something certain, positive:On m'assure que vous avez reçu They assure me that you have rethe lettre de votre père, ceived a letter from your father. Courir. Croire. Daigner. Déclarer. Regarder. (2.) The participle past accompanied by the auxiliary être agrees in gender and number with the subject of the verb, whether the subject be placed before or after it [see § 135 (1)) :Quant il vit l'urne où étaient When he perceived the urn in renfermées les cendres d'Hippias, which were enclosed the ashes of il versa un torrent de larmes, Hippias, he shed a torrent of tears. (3.) The participle past, having avoir as its auxiliary, never agrees with the nominative:Mes amis ont parlé; leurs cœurs sont attendris, Acharner (s'). Admettre. Aguerrir (s'). Condescendre. Aider. Consentir. Aimer. Consister. Appliquer (s'). Conspirer. Habituer (s'). Apprendre. Consumer. Apprêter (s'). Contribuer. Hésiter. Résigner (se). Aspirer. Convier. Instruire. Rester. This sentence is correct, because aimer, instruire, and louer being active verbs, govern one and the same case, the direct regimen. (2.) But when the verbs require different regimens, they cannot govern one and the same noun, and therefore another form must be given to the sentence. We could not say in French-Un grand nombre de vaisseaux entrent et sortent de ce port tous les mois, a great number of vessels enter and go out every month, because the verb entrer reaches its ns of the preposition dans, and sortir by means de. We should say: (5.) But if the direct regimen is placed after the participle, this participle remains invariable: J'ai reçu votre lettre, C'est la vérité elle-même qui lui a dicté ces belles paroles, I have received your letter. It is truth itself which has dictated to him those fine words. KEY TO EXERCISES IN LESSONS IN FRENCH. 1. Have you collected many people at your house? 2. Very few people came. 3. At what hour will they serve the dinner to-day? 4. It will be served as soon as all our company is come. 5. Has the captain all his crew on board? 6. No, Sir; he has sent some people on shore. 7. Do your people rise early? 8. Every day I must awake all my people. 9. The Russians lost three times more men than the Swedes. 10. Where is your mother? 11. She is in the drawingroom; there is company with her. 12. Everybody can travel as I do. 13. So goes the world. 14. She waits to leave the world until the world has left her. 15. Are your people back from the country? 16. We expect our people to-day. 17. Is there here a society of men of letters? 18. No, Sir; there is only a society of lawyers. 19. Do you know those worthy people? 20. I believe they are military men. 21. Such are people in these times. 22. Such people; such patrons. 23. All my people are ill. 24. We must put up with everybody. EXERCISE 184 (Vol. III., page 319). 1. Y a-t-il beaucoup de monde chez votre frère? 2. Il n'y a pas beaucoup de monde. 3. Ce jeune homme médit-il de tout le monde? 4. Il ne médit de personne. 5. Avez-vous amené beaucoup de monde avec vous? 6. Nous n'avons amené que peu de monde. 7. Y a-t-il du monde avec Mme, votre mère? 8. Il n'y a pas de monde avec elle. 9. Qui vous a dit cela? 10. Tout le monde le dit. 11. Le monde est-il venu? 12. Le monde n'est pas encore venu. 13. Mme, votre mère a-t-elle congédié deux domestiques? 14. Elle a congédié tout son monde. 15. Connaissez-vous ces gens? 16. Je les connais trèsbien; ce sont de fort braves gens. 17. Quand il voyage, il loge toujours chez de bonnes gens. 18. Y a-t-il de sottes gens ici? 19. Ilya de sottes gens partout. 20. Éveillez-vous vos gens tous les matins? 21. Oui, Monsieur; il faut que je les éveille tous les jours. 22. Qu'estce-que M. votre frère peut avoir à démêler avec ces gens? 23. Ce sont les meilleures gens du monde. 24. Y avait-il beaucoup de monde à l'église ce matin? 25. Il n'y avait pas beaucoup de monde. 26. Vos gens sont-ils malades? 27. Oui, Monsieur; tous mes gens sont malades. 28. Il y a ici une société de gens de lettres. 29. Il yaà Paris plusieurs sociétés de gens de robe. 30. Quels braves gens! 31. Quelles bonnes gens! 32. Attendez-vous vos gens aujourd'hui ? EXERCISE 185 (Vol. III., page 350). 1. Is it a new coat that your son wears? 2. It is a new cost, the cloth is very fine. 3. Are not the sleeves too short? 4. I believe that the sleeves are too short and the skirts too long. 5. Has not the country its advantages? 6. I like the country, I know its advantages. 7. Paris has its pleasures. 8. I like Paris, I know its pleasures. 9. Does that surgeon understand medicine? 10. He knows nothing at all about it. 11. Are you expert in medicine? 12. I do not understand it. 13. I do not know it. 14. I understand nothing about it. 15. Have you succeeded in making yourself understood ? 16. We have not. 17. My neighbour is a worthy man, and I agree very well with him. 18. Imposing silence on certain people is a greater miracle than making the dumb speak, 19. Do you know from what country that ENGLISH LITERATURE. man is? 20. He conceals his country and birth. 21. Through the power of reason she acquired the art of speaking and of being silent. 22. Will you hold your tongue, impertinent woman? you always come and mix your impertinences in everything. 23. He who is silent EXERCISE 186 (Vol. III., page 350). consents. 1. Avez-vous un très-bon jardin ? 2. Nous en avons un très-grand, mais la terre n'en est pas bonne. 3. L'habit de votre frère est-il neuf ? de se taire. ENGLISH LITERATURE-XXII. 21. 23. THE REVOLUTION AND THE AUGUSTAN PERIOD: PROSE THE great Revolution of 1688 not only completed the great The central figure in the world of thought and of letters in the years which followed the Restoration is that of John Locke. This great man was born in 1632. He was educated first at Westminster School, and afterwards at Christchurch, Oxford. At Oxford he spent many years after he had taken his degree, devoting himself mainly to the study of natural science, and especially of medicine, in which he became very proficient. After the Restoration, Locke was frequently employed in the public service abroad and at home; and was involved in the political conflicts of the time, attaching himself to the cause and following the fortunes of Lord Shaftesbury, the able but unscrupulous and ambitious leader of the Protestant party. After the final fall of Shaftesbury, and the triumph and accession to the throne of his enemy the Duke of York, Locke's position in England became unsafe, and he retired to Holland, where he remained as long as James II. occupied the throne. In 1688, immediately upon the change of government, Locke returned to England. He was soon appointed to an important and lucrative post in the public service, as a member of the Council of Trade, an office which he retained as long as his health allowed of his doing so. After leaving the public service, he passed the remaining years of his life in the country in learned retirement. He died in 1704. The works of Locke are numerous, and their subjects somewhat various; but the same tone and spirit pervades them all 287 a spirit of earnest but temperate devotion to the cause of liberty in politics, in philosophy, and in religion. All show the same originality, vigour, and breadth of thought and clearness of reasoning; and in all his style is simple and nervous, though sometimes, perhaps, too idiomatic and too full of metaphor to be consistent with philosophical exactness or quite in keeping with the dignity of his subject. Locke's "Letters on Toleration" constitute the most systematic and philosophical argument in favour of toleration which had as yet appeared. His "Treatise of Civil Government" is an attempt to determine the true basis on which civil government rests, and the limits within which it ought to be restricted. A school of writers in his day had adopted, without much inquiry, a theory of the origin of government-which, however, modern inquiry has shown to be historically quite correct-that the family is the oldest of institutions, and the father of the family the oldest of rulers; that the family became the tribe, the tribe the nation; and that so the family organisation and the power of the father are the root from which have been developed the political state and the authority of kings. But not content with teaching this as an historical theory, in which aspect it is perfectly correct, these writers went on to make a most mischievous practical application of it. They taught that, by some divine right or inherent necessity, the power of a king must always remain as sacred and as unlimited as the power of the parent in its most primitive form. Hence they taught the duty of absolute obedience to kings, and denied the rights or liberties of subjects. To meet such views Locke's very powerful treatise was written. In it he places all government upon its only rational basis, the common benefit of all. But he sometimes fails to distinguish between the two wholly distinct questions, the question, How did governments in fact originate? and the question, Why ought they now to be maintained, and what limits ought to be assigned to them? And upon matters of history Locke is often less sound than his opponents. Very similar in spirit is the Essay on Education," which shows much liberality of spirit and a strong desire to throw off the narrowness which distinguished the system of education prevailing then even more than it does in the present day. "Essay on the Reasonableness of Christianity" is a calm and serious argument on the subject which its title expresses; and it gives a greater insight into Locke's religious views and feelings than any other of his works. 66 The But the work which has secured for Locke his great and lasting reputation, and given him a place among the greatest thinkers, is the "Essay on the Human Understanding." A critical examination of this remarkable book would be out of place in these "Lessons on English Literature;" it belongs rather to the history of philosophy. Locke was not the first who attempted to map out with fulness and precision the field of the human intellect, and to trace our ideas to their sources. Many labourers in the same work had preceded him on the Continent, and some in England; but no writer had ever approached Locke in clearness of thought, soundness of method, or variety and originality of illustration. The truth of Locke's general theory has always been and will probably always be a matter of dispute, and those who agree with his general conclusions will always find something to dissent from among his detailed opinions. But even those most hostile to his philosophical system admit the power of his work and the value of his discussions of the most difficult questions. Few books have exercised so profound an influence upon European thought. In the domain of mathematics and experimental philosophy the genius of Sir Isaac Newton stood supreme at the same epoch; nor did he stand by any means alone in the cultivation of these branches of science. Nothing more plainly illustrates the spirit prevalent in England after the Revolution than the character of the churchmen and theologians, and the tone of the theological teaching of the period. The school of divines prominent after the Revolution was that which has been characterised as Latitudinarian—a school distinguished by learning, good sense, judgment, and tolerance; very free from bigotry, narrowness, and superstition; but falling short, perhaps, of that high standard of zeal and enthusiastic devotion which has sometimes prevailed among men intellectually inferior. Among theologians of this class a high place must be assigned to Gilbert Burnet, Bishop of Salisbury. Burnet was the religious adviser of the Princess Mary in Holland, and came with her to England on the accession of herself and her husband to the throne; and was soon after raised to the episcopal bench. As a theologian he is best known by his "Exposition of the Thirtynine Articles." But his most important contributions to literature are his two historical works-the "History of the Reformation and "History of his own Times," both of them works of great value, though their historical importance is greater than their literary merit. One of the most eminent and probably the ablest theologian of the school which became predominant at the Revolution was Isaac Barrow, though he himself died too soon to witness that great event. Barrow was born in London in 1630, his father being a linendraper in that city. He received his earlier education at the Charterhouse, and afterwards was entered first at Peterhouse and subsequently at Trinity College, Cambridge. Cambridge was thenceforth his home for many years; during which time his fame as a profound scholar and linguist, as well as a man of great scientific genius, especially in the department of mathematics, became widely known. He filled the post of professor of mathematics, and as such was the teacher of the great Newton, who succeeded him in his professorship. He was subsequently chosen as Master of Trinity College. During the latter years of his life he to a great extent forsook his purely scientific pursuits, and devoted his great powers to the duties of a preacher and religious teacher; and among English divines few have been his equals in genius. His learning was great, but is never obtruded upon the reader. His reasoning powers were of the highest order, and in his sermons sound reasoning and judgment always hold their legitimate supremacy; they are never subordinated either to feeling or to fancy. His style is characterised by a force and clearness, a manly dignity, and a severe purity of taste which, combined with his powers of thought, place him in the highest rank of orators. His sermons will always rank with the writings of Hooker and Jeremy Taylor, the great classics of the English Church. Barrow died, at a comparatively early age, in 1677. Archbishop Tillotson enjoyed, during his life, a fame and estimation as a preacher surpassed by few, and was among the most influential churchmen of his day; nor has the popularity of his writings altogether passed away. He was a man of great liberality and tolerance, and was raised to the archbishopric of Canterbury by William III. Of a very different school was Robert South. He was the son of a London merchant, and was born near London in 1633. Having received the rudiments of learning at Westminster School, he went to Oxford, and maintained his connection with that university for many years. He adopted the views of the courtly and anti-popular party, and took an active part in the conflicts of the time. After the Restoration he became chaplain to Lord Chancellor Clarendon, and partly through his influence received several successive preferments in the church from the Government of Charles II. The latter years of South's life were spent in retirement, and he died in 1716. His fame as a preacher was very great, and his sermons are still read with great pleasure for the force and beauty of his style. But as sermons his productions are to a modern taste deformed by what in his own day seems to have been regarded as a beauty, a vein of sarcastic wit, sometimes almost overstepping the limits of buffoonery. The most eminent in literature of the churchmen of the next generation was Bishop Berkeley, a man equally distinguished for his genius in science and philosophy, and for the purity and nobility of his life and character. It was not without reason that Pope attributed "To Berkeley every virtue under heaven." George Berkeley was born in Ireland, in the county of Kilkenny, in 1684. He was educated at Trinity College, Dublin, of which college he in due time became a Fellow. He then commenced those philosophical writings which have secured his lasting fame; and upon his removing to London a few years later, he was eagerly welcomed by all those most eminent in the world of thought and literature. The lofty earnestness of his character impressed the most frivolous, while its beauty and gentleness conciliated the most hostile. But Berkeley was not one of these who sought to use their popularity to secure any personal advantage. Having been promoted to the deanery of Derry, a lucrative as well as dignified post, he resigned this office with all its advantages, and abandoned that position in society which he was so well qualified to adorn, in obedience to the guidance of conscience, and went out to the West Indies, to place himself at the head of a sort of missionary college, intended to facilitate the Christianisation of the natives of North America. But the miserable pittance which had been promised to Berkeley for the maintenance of his college and the support of himself by the Home Government, not being paid him, the enterprise failed, and he was forced to return home. He afterwards became Bishop of Cloyne, in Ireland. He died in 1753. Although it would be a grave omission in these sketches of literature if we were to omit so great a writer as Berkeley, it would not less be a departure from our plan if we were to attempt any analysis of his philosophical system, or any criticism of his writings. Those writings cover a very wide field, from the broadest speculations as to the nature, and origin of our ideas, and their connection with an external universe on the one side, to the most exact and detailed investigation of the phenomena of physical science on the other. By the admission of opponents, no less than of those whose views are most in harmony with his own, few thinkers have surpassed Berkeley in boldness, acuteness, and originality, or have left a deeper impression upon the course of European thought. Few careers have been more extraordinary in their vicissitudes than that of Henry St. John, Lord Bolingbroke. Born in 1678, the son of a baronet of ancient family and competent fortune, though he early gave proof of the possession of brilliant ability, he was in youth little distinguished except for his extravagance and dissipation. But having entered Parliament and devoted his great energies to politics, he was soon without a rival in eloquence and all the brilliant qualities which contribute to parliamentary success. He was a leader in that remarkable literary circle of which Pope and Swift were members. He had early allied himself with Harley, afterwards Earl of Oxford, and they soon became the leaders of the extreme Tory party. In the administration of Oxford, St. John, who had been raised to the peerage as Lord Bolingbroke, held the office of Secretary of State, and as such bore the chief share in bringing about the peace of Utrecht. On the death of Queen Anne and the accession of George I., Bolingbroke was disgraced and impeached, and fled from the storm. That he had been guilty of maintaining a treasonable correspondence with the exiled Stuart family, there can be little doubt, and the unpopularity of the peace which he had been instrumental in bringing about exposed him to the indignation of the country. He was condemned in his absence, and passed many years abroad, for some time being actually in the employment of the Pretender, though he soon quarrelled with him, and was ever after loud in his condemnation of Jacobites. After some years his attainder was reversed, and he was enabled to return to England. He strove hard to regain the political influence which he had once enjoyed, but in vain; and the closing years of his life were spent in retirement. He died in 1751. Bolingbroke's works are numerous. Many of them were addressed to merely passing questions, and are now of little interest. A very large proportion consists of attacks more or less direct upon Sir Robert Walpole, Bolingbroke's great rival and enemy. Others again, and these were published after the death of the author, are attacks upon religion; for in matters of religion Bolingbroke was an avowed unbeliever. The most permanently interesting of his works are those which deal with historical questions and with political principles, such as his "Letters on the Study and Use of History," and his "Idea of a Patriot King." The last-mentioned is now, probably, more read than any other of Bolingbroke's writings; and it well deserves its popularity. This essay shows no profound knowledge of history, nor any very deep thought or subtle analysis; its views are for the most part tolerably obvious, and much of the essay is evidently of the nature of a party attack, rather than an impartial political treatise. But it contains, on the whole, a very noble picture of what a perfect king should be to his country; and it is an excellent example of Bolingbroke's sus tained and impressive eloquence, his wealth of illustration, and beauty and harmony of language. It shows him as one of the greatest masters of English style; and for this reason no man of taste can read the essay without thorough enjoyment. ACOUSTICS. 289 ACOUSTICS.-III. Having now ascertained the velocity at which sound travels, we can easily determine the length of the sonorous waves. It RESONANCE-REFLECTION OF SOUND-ECHOES-REFRACTION is, however, important for us first of all to obtain a clear idea of OF SOUND. WE must now inquire as to the rate at which sound travels through the air, and we shall then be able to calculate the length of the waves produced by any given note. This inquiry is rather a difficult one, as there are many disturbing causes, such as the temperature of the air, the amount of watery vapour present in it, and the pressure as indicated by a barometer. A calm night is usually selected for the experiment, as the air is then much more quiet. Two stations of observation are chosen, several miles apart, but so situated that each can be seen from the other. Cannons or guns are then discharged at regular intervals of about ten minutes, and, since the passage of light is practically instantaneous, the moment of firing is thus seen, and the distant observers note very accurately, by means of a chronometer, the interval between seeing the flash and hearing the report. The true distance between the stations is then measured, and, dividing this by the number of seconds, the velocity of the sound is ascertained. In an experiment of this nature tried in France many years ago, the distance between the observers was 20,354 yards, and, as the mean of several observations, the time occupied by the sound in travelling this distance was found to be 54.6 seconds. This gives a velocity of 1,118 feet a second, when the air is at 60°, that being the temperature during the experiment. As the temperature increases, the speed increases likewise at about the rate of a foot a second for every degree. Generally, then, we may state the velocity of sound in the air at 32° to be 1,090 feet a second, and to increase one foot for every degree that the temperature is raised. In other gases the velocity of sound is somewhat different: we can, however, easily determine it, since it is found to vary inversely as the square roots of their densities. Hydrogen, for example, is sixteen times less dense than oxygen, and sound travels through it at four times the speed. An increase of density thus serves to diminish the velocity, and this is why sound travels more slowly in air at a low temperature. are In water, the sound-waves propagated at a rate of about 4,700 feet a second, and many solids convey them much more rapidly; along an iron rod, they travel nearly 17,000 feet in the same time. A A B M. their nature. In water, each wave consists of an elevation and a corresponding depression, and the length is measured from crest to crest. In sound-waves, we have in place of these an area of condensation and one of rarefaction, and the length is measured from one centre of compression to the next. Now sound, as we have seen, travels 1,120 feet a second in air at the temperature of 60°, ard a C tuning-fork-that is, one sounding the note an octave above middle C-produces 512 vibrations in the same time. Dividing 1,120 by this, we find the length of the waves produced by that note to be about 2 feet 2 inches. An octave lower, the waves are about double the length, or about 4 feet 4 inches. This calculation may easily be verified by the student in a rather remarkable way, and in doing so he will obtain a good illustration of the manner in which a sound may be increased by resonance. Take a tall glass jar, A (Fig. 12), and having struck the tuning-fork, B, hold it over the mouth of the jar, as shown. The sound will probably be unaffected. Now gently pour in water from a jug, making as little splash as possible; when it attains a certain height, the sound will be found to burst suddenly forth with greatly increased power. On pouring more water in, the sound sinks again to its former intensity. Ascertain, by repeating the experiment, the exact point at which the maximum intensity is attained, and then measure its depth from the top of the jar. If we are using a C fork, we shall find this depth to be 6 inches, or just one-fourth the length of the wave. The return wave, therefore, is exactly synchronous with the return vibrations of the fork, and thus the sound is greatly increased and swells out with augmented intensity. When the water is at a different level the vibrations interfere with one another, and clash to a certain extent. The manner in which the power of any sound is increased by resonance is well shown by an apparatus devised by Savart, and shown in Fig. 13. A large open-mouthed bell, A, is set in B a vibration by drawing a violin-bow across its edge. Close to it is a hollow cylinder, B, the length of which can be adjusted by means of a sliding tube. This cylinder is mounted on universal joint, so that it can be turned in any direction, and its distance from A can be adjusted The intensity Fig. 12. good illustration of the different rates at which gases and solids conduct sound may be observed by standing near a long iron railing, and getting a friend at a distance to strike it a violent blow. Two distinct sounds will be perceived, the first caused by the vibrations conducted along the railing, while the other has travelled through the air, and hence arrives considerably after the first. In blasting operations, two concussions are often heard, from a similar cause, the one being conveyed by the solid rock, and the other transmitted through the air. In substances which exhibit a fibrous or crystalline structure, the sound travels in different directions at different speeds. Along wood, for instance, it is conveyed in the direction of the fibres nearly four times as rapidly as across them. VOL. VI. Fig. 14. by means of the slide, c, on which it is carried. It is stated that in ancient times large metal vessels were placed in theatres upon the stage, in order to increase, by their resonance, the power of the actors' voices. In the present day care is taken, in the construction of large buildings, to give them such a form as to render the speaker's voice audible with the least effort to himself. In many respects waves of sound are closely analogous to 149 |