LESSONS IN PHYSICS. turpentine without smoke, and obtained a flame of which the whiteness far surpasses that of a Carcel lamp. With pure oxygen, the flame became of a dazzling white, and gave a light 150 times greater than oil-gas. Drummond-light.-The application of the oxyhydrogen blowpipe for purposes of illumination, by throwing an ignited jet of the mixture of oxygen and hydrogen upon a cylinder of lime, is well known under the name of the Drummond light. In this case, the nozzle or orifice of the blowpipe must be pointed upwards, in order to allow the flame to play upon the lime. In all practical applications of the oxyhydrogen blowpipe, the plan of employing the gases mixed beforehand in the reservoirs has been abandoned, and the original plan of the inventor, Dr. Hare, has been again adopted. The gases are generally kept in metallic reservoirs, and their regular and steady efflux is effected by hydrostatic pressure and stopcocks immersing the gasometers or reservoirs in water. For larger purposes, closed reservoirs may, in large cities, where such conveniences present themselves, be connected by a pipe and stop-cock with the pressure of the city water-works. The hydrogen may in many cases be employed as obtained directly from a large self-regulating reservoir, containing The facility with which zinc and dilute sulphuric acid. large india-rubber bags are now manufactured, and the convenience and nicety with which they are filled with the gases, and these, in like manner, retained and subsequently discharged by superposed weights, has lately introduced them into extensive use for the purposes above-mentioned. From the reservoirs, the gases are delivered by pipes furnished with stop-cocks, at the orifices where the combustion takes place. Near these, the pipes are either made to combine by being united into one, as the two branches of the letter y; or the ton. pipe with the oxygen terminates concentrically within the Gas-light. While oil-lights were gradually reaching a The illuminating gas is chiefly composed of carburetted hydrogen, of which the density is 0.6 of that of air, and is obtained by the destructive or dry distillation of coal. The following table will give our readers an idea of the products arising from this process. PRODUCTS OF THE DRY DISTILLATION OF COAL. Naphthalin, paranaphthalin, benzin, leukolin, etc. Residue: Pitch. (Water, ammonia, carbonic, acetic, sulphurous, muriatic, Ammonia and some acids. Ammonia. Sulfhydric, cyanhydric, etc., acids. Carbonic, sulphurous, sulfhydric, and other acids. Residue: Coke, consisting of carbon and earthy matter. For The best coal for making illuminating gas is considered to by the distillation of bituminous coal, is composed chiefly of be that known by the name of bituminous or fatty coal, burn-protocarburetted hydrogen, carbonic oxide, carbonic acid, nitroing with a long flame; some kinds yielding upwards of 8,000 gen, oleaginous matters more or less easily condensed, ammocubic feet of gas per ton of coals: but that kind of coal called niacal and sulphuretted compounds, and tarry substances. cannel coal yields from 10,000 to 12,000 cubic feet of gas per As in this state the gas exhales a very fetid smell, and the The distillation is effected in large cylindrical cast-iron products of the combustion are themselves odoriferous, it is retorts, ranged parallel to each other, to the number of three necessary to purify the gas, especially for domestic use. or five, over the same furnace; each retort being provided this purpose it is conveyed from the retort into a small barrel, with a vertical tube, through which the coal is introduced, partly filled with water, through a pipe entering into the and to which the pipe is fastened for the discharge of the gas. liquid about one-eighth or a quarter of an inch, so as to interwhich the gas is collected. The greater part of the water and The temperature of the furnace must be kept at a bright cept the communication of the retort with the apparatus in cherry-red heat, because if it be greater, the gas does not give so much light; for the bicarburetted hydrogen gas and tar condenses in the barrel, which is furnished with a disthe very volatile oils, to which the brilliancy of the flame is charging pipe to maintain a constant level in the barrel, and chiefly owing, deposit carbon, and are converted into proto- to allow the excess of the condensed products to escape. The carburetted hydrogen, the combustion of which gives but gas, on leaving the barrel, traverses a series of pipes more or little light; and if, on the contrary, the temperature be too less cooled, in which the condensation of the water and tar low, a large quantity of essential oil is formed, which cannot is completed, and is then conducted through boxes containing remain in suspension in the gas, but is deposited in the refri- metallic salts, chiefly chloride of manganese and sulphate of But these purifi gerators. The duration of the distillation varies according to iron, which decompose the ammoniacal salts and isolate the the quality of the coal, its hygrometric state, and the arrange- sulfhydric acid; finally, it passes through other boxes coninent of the apparatus; and the residue consists of a light taining hydrated lime, which absorbs the sulfhydric gas, the coke, much used for domestic purposes. The gas produced carbonic acid and the other acid vapours. cations must not be carried too far, otherwise the gas will be deprived of too much of its oily vapours, and its illuminating pover would be sensibly diminished. The gas is collected in gas-holders called gasometers (which resemble immense bells), made of sheet-iron, and inverted in cisterns of corresponding size, built of hydraulic mason-work, and filled with water. The weight of the gasometer is partially balanced by counterpoises, which leave it only the weight necessary to produce the pressure required for the distribution of the gas to the various jets it has to feed. The pressure is composed of the resistance which the gas meets in circulating through pipes, generally of great extent; the excess of elastic force which it must retain in order to feed the jets; and the pressure necessary to drive it to the highest points, of which the level is frequently higher than that of the gasometer. The last pressure may be easily calculated after ascertaining the difference, h, of the level of the gasometer and of the highest jet, and the density of the gas as compared with that of the air, when it is equal to the weight of a column of water hd whose height is represented by The height of a gaso770. meter is generally equal to the radius of the base. The largest gasometers are about 100 feet in diameter. exterior appearance of the gas-meter. The gas enters at B and goes out at A. The pipes which conduct the gas may be made of cast-iron, stone-ware, iron-plate, covered with bituminous mastic, galThe burners have genevanized iron-plate lead, or zinc. rally the form of those of Argand's lamp, in order that they may have the double current of air. This burner is pierced with fifteen or twenty holes of about one-twentieth of an inch or less in diameter, the diameter of its central space being rather less than an inch. LESSONS IN READING AND ELOCUTION. EXERCISES ON EXPRESSIVE TONE (continued). INTERESTING ADVENTURE, I wandered far into the bare prairie, which was spread around me like an ocean of snow, the gentle undulations here and there having no small resemblance to the ground swell. When the sun took off his night-cap of mist (for the morning was cloudy), the glare of the landscape, or rather snowscape, was absolutely painful to my eyes; but a small veil of green crape obviated that difficulty. Toward noon I was aware of a buffalo, at a long distance, turning up the snow with his nose and feet, and cropping the withered grass beneath. I always thought it a deed of mercy to slay such an old fellow, he looks so miserable and discontented with himself. As to the individual in question, I determined to put an end to his long, turbulent, and evil life. The following economical mode of manufacturing gas has recently been adopted in Manchester. Three or five retorts are used, the central one of which is charged with metallic iron and coke, or with coke alone, and traversed by a current of steam, which is thus decomposed into hydrogen and oxygen. These gases are led through the other retorts, in which coal is undergoing the process of distillation, when the free hydrogen combines with the nascent carbon resulting from the decomposition of different hydro-carbons, and forms olefiant To this effect, I approached him as a Chinese malefactor gas, which imparts a great brilliancy to the flame. The gas approaches a mandarin-that is to say, prone, like a serpent, thus manufactured is called hydro-carbon gas, and its illumi-But the parity only exists with respect to the posture; for the nating power is double that of ordinary gas under the same aforesaid malefactor expects to receive pain, whereas I incircumstances, while the cost of production is at least not tended to inflict it. He was a grim-looking barbarian-and, greater than in the former case. if a beard be a mark of wisdom, Peter the Hermit was a fool to him. So, when I had attained a suitable proximity, I appealed to his feelings with a bullet. He ran-and I ran; and I had the best reason to run-for he ran after me, and I thought that a pair of horns might destroy my usual equanimity and equilibrium. In truth, I did not fly any too fast, for the old bashaw was close behind me, and I could hear him breathe. I threw away my gun; and, as there was ro tree at hand, I gained the centre of a pond of a few yards area, such as are found all over the prairies in February. In the use of gas illumination on a large scale, it became necessary to employ an apparatus simple and not liable to get out of order, for measuring the quantity furnished to any establishment, public or private. For this purpose the gasmeter was invented. It consists of a kind of bucket-wheel with its axis placed horizontally, and immersed in a cylinder filled with water up to the axis. A. tube conducts the gas to this axis; the gas then passes through the water and fills the bucket placed in the upper part of the cylinder, whence it escapes through another tube properly arranged for the purpose. As soon as the first bucket is emptied, a second is filled in the same manner; and this admission and discharge of the gas is regularly continued. The gas communicates a motion of rotation to the wheel, and the quantity of gas delivered is ascertained by the number of revolutions made by the apparatus, a number which is registered by the wheel-work put in motion by the axis of the bucket-wheel. Fig. 237 shows the Here I stood secure, as though in a magic circle, well knowing that neither pigs nor buffaloes can walk upon ice. My pursuer was advised of this fact also, and did not venture to trust himself on so slippery a footing. Yet it seemed that he was no gentleman; at least he did not practise forgiveness of injuries. He perambulated the periphery of the pond, till I was nearly as cold as the ice under me. It was worse than the stone-jug, or the Black-hole at Calcutta. Ah! thought I, if I only had my gun, I would soon relieve you from your post. But discontent was all in vain. Thus I remained, and thus he remained, for at least four hours. In the mean while, I thought of the land of steady habits; of baked beans, and pumpkins, and codfish on Saturdays. There, said I to myself, my neighbour's proceeding would be reckoned unlawful, I guess; for no one can be held in custody without a warrant and sufficient reason. If ever I get back, I won't be caught in such a scrape again. Grief does not last for ever; neither does anger; and my janitor, either forgetting his resentment, which, to say the truth, was not altogether groundless, or thinking it was useless, or tired of his self-imposed duty, or for some reason or other, bid me farewell with a loud bellow, and walked away to a little oasis that was just in sight, and left me to my meditations. I picked up my gun, and followed. He entered the wood-and so did I, just in time to see him fall and expire. The sun was setting; and the weather was getting colder and colder. I could hear the ground crack, and the trees split, with its intensity. I was at least twenty miles from home; and it behoved ine, if I did not wish to "wake in the morning and find myself dead," to make a fire as speedily as possible. I now first perceived that, in my very natural hurry to escape from my shaggy foe, I had lost the martin-skin wherein I carried my flint, steel, and tinder. This was of little consequence; I had often made a fire by the aid of my gun before, and I drew my knife and began to pick the flint. Death to my hopes-at the very first blow I struck it ten yards from the lock, and it was lost for ever in the snow. "Well," said I to myself, "I have cooked a pretty kettle of fish, and brought my calf's head to a fine market. Shall I furnish those dissectors, the wolves, with a subject, or shall cold work the same effect on me that grief did upon Niobe? Would that I had a skin like a buffalo! Necessity is the spur, as well as the mother, of invention; and, at these last words, a new idea flashed through my brain like lightning. I verily believe that I took off the skin of my victim in fewer than ten strokes of my knife. Such a hide entire is no trifle; it takes a strong man to lift it;-but I rolled the one in question about me, with the hair inward, and lay down to sleep, tolerably sure that neither Jack Frost nor the wolves could get at me, through an armour thicker and tougher than the sevenfold shield of Ajax. Darkness closed in; and a raven began to sound his note of evil omen from a neighbouring branch. "Croak on, black angel," said I; "I have heard croaking before now, and am not to be frightened by any of your colour." Suddenly a herd of wolves struck up at a distance, probably excited by the scent of the slain buffalo. "Howl on," said I; "and, being among wolves, I will howl too-for I like to be in the fashion but that shall be the extent of our intimacy." Accordingly, I uplifted my voice, like a pelican in the wilderness, and gave them back their noise, with interest. Then I lay down again, and moralised. This, thought I, is life. What would my poor mother say, if she were alive now? I have read books of adventure, but never read anything like this. I fell asleep, without further ado.-Snelling. THOUGHTS ON POLITENESS. The common notion about politeness is, that it is a thing of the body, and not of the mind; and that he is a polite man who makes certain motions in a graceful manner, and at proper times and places. We expect the dancing master to teach our children "manners," as well as the art of cutting awkward capers to music. But the truth is, that we degrade politeness by making it anything less than a cardinal virtue. The happiness of life is made up of an infinite number of little things, and not of startling events and great emotions; and he who daily and hourly diffuses pleasure around him by kind offices, frank salutations, and cheerful looks, deserves as well of his species, as he who, neglecting or despising all these, makes up for it by occasional acts of generosity, justice, or benevolence. Besides, the opportunity of doing great things but rarely occurs, while a.man has some dozens of chances, every day of his life, to show whether he be polite or not. A truly polite man must, in the first place, have the gift of good sense, for, without that foundation, it is idle to think of rearing any, even the smallest superstructure. He must know when to violate that code of conventional forms which common consent has established, and when not; for it is equally a mark of weakness to be a slave to these forms or to despise them. He must have penetration and tact enough to adapt his conversation and manner to circumstances and individuals; for that which is politeness in the drawing-room, may be downright rudeness in the bar-room or the stage-coach, as well as the converse. Above all, he must have that enlarged and catholic spirit of humility, which is the child of self-knowledge, and the parent of benevolence (indeed, politeness itself is merely benevolence seen through the little end of a spy-glass), which, not content with bowing low to this rich man.or.that fine lady, respects the rights, and does justice to the claims, of every member of the great human family. As for the fastidious and exclusive persons, who look down upon a man created and upheld by the same power as themselves, and heir to the same immortal destinies, because he does not dress in a particular style, or visit in certain houses, they are out of the question. If they are too weak to perceive the grotesque absurdity of their own conduct, they have not capacity enough to master the alphabet of 'good manners. If angelic natures be susceptible of ludicrous emotions, we know of nothing more likely to call them forth than the sight of an insect inhabitant of this great ant-hill assuming airs of superiority over his brother emmet, because he has a few more grains of barley in his granary, or some other equally cogent reason. Of the gentlemen, young and old, whiskered and unwhiskered, that may be seen in Regent-street any sunshiny day, there is not one who does not think himself a polite man, and who would not very much resent any insinuation to the contrary. Their opinion is grounded on reasons something like the following. When they go to a party, they make a low bow to the mistress of the house, and then look round for somebody that is young and pretty to make themselves agreeable to. At a ball they will do their utmost to entertain their partner, unless the fates have given them to some one who is ugly and awkward; and they will listen to her remarks with their most bland expression. If they are invited to a dinner party, they go in their best coats, praise their entertainer's wine, and tell the lady they hope her children are all well. If they tread on the toes of a well-dressed person, they will beg his pardon. They never spit on a carpet; and, in walking with a lady, they always give her the inside; and, if the practice be allowable, they offer her their arm. So far, very good; but I must always see a man in certain situations before I decide whether he be polite or not. I should like to see how he would act if placed at dinner between an ancient maiden lady and a country clergyman with a small salary and a rusty coat, and with some distinguished person opposite to him. I want to see him on a hot and dusty day, sitting on the back seat of a stage-coach, when the driver takes in some poor lone woman, with, may be, a child in her arms, and tells the gentlemen that one of them must ride outside and make room for her. I want to be near him when his washerwoman makes some very good excuse to him for not bringing home his clothes at the usual time, or not doing up an article in exactly the style he wished. I want to hear the tone and emphasis with which he gives orders to servants in steam-boats and taverns. I mark his conduct when he is walking with an umbrella, on a rainy day, and overtakes an old man, or an invalid, or a decent-looking woman, who are exposed, without If he be in company protection, to the violence of the storm. with those whom he thinks his inferiors, I listen to hear if his conversation be entirely about himself. If some of the number be very distinguished, and some quite unknown, I observe whether he acts as if he were utterly unconscious of the presence of these last. These are a few, and but a few, of the tests by which I try a man; and, I am sorry to say, there are very few who can stand them all. There is many a one who passes in the world for a well-bred man, because he knows when to bow and smile, that is down in my tablets for a selfish, vulgar, unpolite monster, that loves his own little finger better than his neighbour's whole body. Put any man in a situation where he is called upon to make a sacrifice of his own comfort and ease, without any equivalent in return, and you will learn the difference between true politeness, that sterling ore of the heart, and the counterfeit imitation of it, which passes current in drawing-rooms. Any man must be an idiot not to be polite in society, so called; for how else would he get his oysters and champagne?-Hillard. ODE ON ART When, from the sacred garden driven, And crossed the wanderer's sunless path. 'Twas Art! sweet Art! new radiance broke Where her light foot flew o'er the ground; And thus with seraph voice she spoke,"The Curse a Blessing shall be found." She led him through the trackless wild, Where noontide sunbeam never blazed; The thistle shrunk, the harvest smiled, And point their spires of faith to heaven. He rends the oak,-and bids it ride, To guard the shores its beauty graced; See towers of strength and domes of taste. And leaps triumphant o'er the grave, He plucks the pearls that stud the deep, With thoughts that swell his glowing soul, In fields of air he writes his name, And treads the chambers of the sky; He reads the stars, and grasps the flame That quivers round the Throne on high. In war renowned, in peace sublime, He moves in greatness and in grace; His power, subduing space and time, Links realm to realm, and race to race.-Sprague. GOD. [The piece which follows is designed for practice in the 'very slow' rate which characterises deep awe. Reverence, solemnity, and awe,-but especially the last,-incline to extreme slowness, great prolongation of single sounds, and remarkably long pauses. The tone of these emotions is deep, although not so peculiarly low as that which was exemplified in the preceding lesson. Length of vowel sounds, and length of pauses, are the main objects of practice in such exercises.] [] O Thou eternal One! whose presence bright All space doth occupy, all motion guide: Unchanged through time's all-devastating flight; Thou only God! There is no God beside! Being above all beings! Mighty One! Whom none can comprehend, and none explore; Who fill'st existence with Thyself alone: Embracing all,-supporting,-ruling o'er,Being whom we call God,-and know no more! In its sublime research, philosophy May measure out the ocean-deep,-may count Thou from primeval nothingness didst call Sprung forth from Thee:-of light, joy, harmony, Thy chains the unmeasured universe surround, And as the spangles in the sunny rays A million torches lighted by Thy hand, Yes! as a drop of water in the sea, All this magnificence in Thee is lost : What are ten thousand worlds compared to Thee? Is but an atom in the balance, weighed Against infinity! Oh! what am I then? Nought! Nought! yet the effluence of Thy light divine, I am, O God! and surely Thou must be ! The chain of being is complete in me: I can command the lightning, and am dust! A monarch, and a slave; a worm, a god! Whence came I here? and how so marvellously For from itself alone it could not be! God! thus alone my lonely thoughts can soar; NIAGARA. Derzhavin. [The following piece is designed for practice in the 'slow' utterance which characterises the tones of sublimity and awe. The 'rate' of voice is not altogether so slow as in the preceding lesson; yet it retains much of that effect which cannot be given without slowness of movement and full pauses. The note, in the style of this lesson, continues low, although not so remarkably deep as in the preceding. The principal object of practice, in this instance, is to secure that degree of 'slow.css stem, which strengthening consists either in the doubling of which marks the tones of wonder and astonishment.] [ ] Flow on for ever, in thy glorious robe Keep silence, and upon thy rocky altar pour Ah! who can dare Every leaf, That lifts itself within thy wide domain, Thou dost make the soul A wondering witness of thy majesty; As if to answer to its God through thee.-Sigourney. LESSONS IN GREEK.-No. XXXVII. BY JOHN R. BEARD, D.D. LIQUID VERbs. The Formation of the Tenses of Liquid Verbs. ! LIQUID Verbs are those whose characteristic is a liquid, namely, A, u, v, or p. Liquid Verbs form the Future active and middle and the First Aorist active and middle without the tense-characteristic o, and yet take the tense-characteristic * in the First Perfect and Pluperfect active; as, σφάλλω (pure stem ΣΦΑΛ), I trip up, stumble σφάλλω, fut. σφαλ-ῶ, aor. 1. ε-σφηλ-α, pf. ε-σφαλ-κα. The Future terminations of liquid verbs, ὤ, οἶμαι (from εσω, tooμai), are circumflexed like the Present active and middle of contracted verbs in εω, as φιλῶ, φιλ-οῦμαι. Liquid verbs have not the Third Future. With few exceptions, the Present of those verbs whose stem-vowel ise, has undergone a strengthening of the pure the A, or the liquid is introduced after the characteristic, as σφάλλω ; stem ΣΦΑΛ, Present σφάλλω, the λ being doubled ; TEμV-w, pure stem TEM, v being introduced to form the Present; or in this, that the root-vowel is either lengthened, namely, is lengthened into i and u into v, as all verbs in ἴνω, ύνω, e.g. κρίνω, I judge, αμύνω, I ward of, σύρω, I draw out, pure stems KPIN (), AMYN (~), XYP (v), or the vowel is changed into a diphthong, that is, a into ai, & into ; e.g. φαιν-ω, I shou, κτειν-ω, I hill, pure stem ΦΑΝ, ΚΤΕΝ. Μεν·ω, I remain, and vɛμ-w, I divide, retain the form of the pure stem; e.g. The First Perfect active is e-opaλ-ka, and the Second Aorist passive is ε-σφαλ -ην. The pure stem appears in the Second Aorist e-opaλ-nv and the Future opăλ-w; yet, since only a few liquid verbs, form the Second Aorist, the pure stem is not, as in the mute verbs, taken from the Second Aorist, but from the Future. Liquid verbs with monosyllabic stems and the stem vowel & take the conversion a in the Second Aorist, in the First Perfect and Pluperfect active, the Perfect and Pluperfect middle or passive, in the First Aorist, First and Second Future passive, as well as in the verbal adjective; and the conversion o in the Second Perfect and Pluperfect; as in στελλω, I send. σTEλλ-w, fut. ØTελ-w, perf. 1. act. ε-oraλ-ka, perf. mid. or pass. ε-craλ-pai, a. 1. pass. -σraλ-On (poet.), a. 2. pass. εστάλην, v. adj. σταλ-τεος. 40×10-w, fut. ¿0ɛp-w, perf. 1. act. ε-plaρ-кa, perf mid. or pass. ε-φθαρ-μαι, a. 2. pass. ε-φθαρ-ην, v. adj. φθαρτος, but perfect 2. -40op-a. Verbs of more than one syllable are not capable of conversion, as αγγελλω, Ι announce, ηγγελκα, ήγγελμαι, ηγγέλθην. Liquid verbs are divided into four classes according to the stem-vowel of the Future, namely, ă, e, i, and : |