beholds this image with the ocular, the last glass produces the effect of the simple microscope, and substitutes for the image ab a second image a'b', which is virtual, and magnified anew. This second image, erect in relation to the first image, is inverted in relation to the object. We may say, then, in regard to this last analysis, that the compound microscope is nothing but the simple microscope, applied not to the object, but to its image already magnified by the first lens. Magnitude-the Micrometer. The magnitude in every optical instrument, is the relation of the absolute size of the image to that of its object. Magnitude in the compound microscope is the product of the respective magnitudes of the objective and the ocular; that is, if the first of these glasses magnify 20 times, and the other 10, the definitive magnitude will be 200. Magnitude depends on the greater or less convexity of the objective and the ocular. It has reached 1,500 in diameter, and even more; but then the image loses in distinctness what it gains in magnitude. In order to obtain images perfectly clear and distinct, the magnitude should not exceed 500 or 600 in diameter, which gives on the surface an image 250 to 360 thousand times greater than the object.

Magnitude may be measured experimentally by means of the micrometer-a small plate of glass, on which are traced with a diamond parallel lines, or 10 of a millimetre asunder. The micrometer is placed before the objective; then, instead of receiving directly on the eye the rays which emerge from the ocular o, we receive them on a plate of glass with parallel faces A (fig. 313), having an inclination of 45°, and we place the eye above so as to see the lines of the micrometer formed by reflection upon a scale divided into millimetres, which is traced on the screen E. Counting the number of divisions on the scale, which correspond to the number of lines of the image, we thence deduce the magnitude. For example, if the image occupy upon the scale 45 millimetres and comprehend 15 lines of the micrometer-supposing that the interval of these beo of a millimetre-the absolute size of the object will be 10%, and that of the image being 45 millimetres, the magnitude will be the quotient of 45 by % or 300. There is in this process, however, a source of error which results from the difficulty of placing the screen exactly

at the distance at which the eye sees the image of the micrometer.

The Compound Microscope of Amici.-We have hitherto described only the principle of the compound microscope. Our attention will now be directed to the principal accessories of this apparatus. Invented in 1620, it has from time to time received a number of improvements. The most important, however, date but thirty years back, and are due chiefly to M. Amici, in Italy, and M. Ch. Chevalier, in France.

Fig. 313.

E

Fig. 314 represents in its essential parts the microscope known as the Microscope of Amici, or the Microscope of Ch. Chevalier. In the ancient microscopes, the tube was always vertical, and the lenses were not achromatic. Amici was the first who adopted a disposition which allows the tube to be horizontal or vertical at pleasure, and it was Chevalier who, in 1823, first applied achromatic lenses to the microscope. Our diagram represents the microscope in the horizontal position, which is generally less fatiguing to the eye. But it may also be placed vertically. For this purpose, the elbow a is elevated, and the large tube A, which bears the ocular, rises to its place upon the objective E. Again, the microscope may have an inclined position. To give it this, we draw the bolt m, which secures the lower part of the apparatus, and we make the whole move on a hinge a, which binds the microscope to a cylindrical column serving for its support.

The fig. 315 shows the position of the glasses and the march

of the rays. The objective E is formed of one, two, or three achromatic lenses, as represented at K, the principal focal distances being from 8 to 10 millimetres. The ocular A H is formed of one simple lens, or two lenses, A and H, these being achromatic or not. It is easy to follow the march of the luminous rays. After being reflected on the mirror M, they meet towards the object, and thence they are directed towards the objective. After traversing that, they encounter a rectangular prism P, in crystal, on the hypothenuse of which they undergo a total reflection; then, taking the direction of the tube GA, the rays fall upon the lens H, and form, beyond, a real and magnified image of the object c. The last lens acts as a simple microscope, substituting for the first image a second image vertical and again magnified.

• The intermediate image н has for its object to collect the too oblique rays which do not fall upon the ocular A. It enlarges the field of the microscope, while rendering the image smaller and more distinct. This glass serves also to correct the defect of achromatism, which the objective more or less presents. As to the aberration of sphericity, it is corrected by the screens m and n (fig. 315), which intercept the rays that tend to cross the lenses too near the edges. In order to extinguish all interior reflection, which could mar the distinctness of the images, the sides of the tube are blackened internally.

If the object be transparent, we illuminate it by means of a reflector placed under the object-bearer; if it be opaque, we use the lens L, supported by the object-bearer, which concentrates the light upon the object.

Finally, the apparatus has several spare oculars and objectives, by which the magnitude may be augmented or diminished. We can also diminish the magnitude by suppressing one or even two of the lenses of the objective.

The microscope has been the cause of the most interesting discoveries in botany, in zoology, and in physiology. Animals whose existence had been altogether unknown, have been observed in vinegar, in water, in the paste of flour, in dried fruits, and in certain kinds of cheese; while the circulation and the globules of the blood have become visible. The microscope is also susceptible of numerous applications in the industrial arts. For example, it furnishes the means

LESSONS IN READING AND ELOCUTION.

No. XIX.

EXERCISES ON EXPRESSIVE TONE-continued.

POETRY.

[Marked for Inflections.]

We believe that poetry, far from injuring society, is one of the great instruments of its refinement and exaltation. It lifts the mind above ordinary life, gives it a rèspite from deprèssing cares, and awakens the consciousness of its affinity with what is púre and noble. In its legitimate and highest efforts, it has the same tèndency and aim with Christianity; that is, to spiritualise our nature. Trùe, poetry has been made the instrument of vice, the pànder of bàd passions; but when genius thus stóops, it dìms its fires, and parts with much of its power; and even when Poetry is enslaved to licentiousness and misanthropy, she cannot wholly forget her trúe vocation. Strains of púre fèeling, touches of tenderness, images of innocent happiness, sympathies with what is good in our nature, bursts of scorn or indignation at the hollowness of the world, passages true to our moral nature, often escape in an immóral work, and show us how hard it is for a gifted spirit to divorce itself wholly from what is good.

Poetry has a natural alliance with our best affèctions. It delights in the beauty and sublimity of outward nature and of the soul. It indeed portrays with terrible energy the excèsses of the passions, but they are passions which show a mighty nature, which are full of power, which command awe, and excite a deep though shuddering sympathy. Its great tèndeney and púrpose, is, to carry the mind beyond and above the beaten, dùsty, weary walks of òrdinary life; to lift it into a pùrer element, and to breathe into it more profound and génerous emotion. It reveals to us the loveliness of nature, brings back the freshness of youthful feeling, revives the rèlish of simple pleasures, keeps unquenched the enthusiasm which warmed the spring-time of our being, refines youthful love, strengthens our interest in human nature, by vivid delineations of its tenderest and loftiest feelings, spreads our sympathies over all classes of society, knits us by new ties with universal being, and, through the brightness of its pròphetic visions, helps faith to lay hold on the future life.

We are aware that is it objected to poetry, that it gives wrong views, and excites fàlse expectations of life, peoples the mind with shadows and illusions, and builds up imagination on the ruins of wisdom. That there is a wisdom against which poetry wars, the wisdom of the sènses, which makes physical comfort and gratification the supréme good, and wealth the chief interest of life,—we do not deny: nor do we deem it the least service which poetry renders to mankind, that it redeems them from the thraldom of this earthborn prudence.

But, passing over this topic, we would observe, that the complaint against poetry as abounding in illusion and decéption is, in the main, groundless. In many poems there is more oftruth, than in many histories and philosophic theories. The fictions of génius are often the vehicles of the sublimest vèrities, and its flashes often open nèw regions of thought, and throw new light on the mysteries of our being. In poetry the lètter is falsehood, but the spirit is often profoundest wisdom. And if truth thus dwells in the boldest fictions of the poet, much more may it be expected in his delinéations of life; for the présent life, which is the first stage of the immortal mind, abounds in the matérials of poetry, and it is the highest office of the bard to detect this divine element, among the grosser pleasures and lábours of our earthly being. The present life is not wholly prosaic, precíse, tàme,* and

A negative sentence, ending with a rising inflection, has the falling slide on its penultimate word or clause.

finite. To the gifted eye it abounds in the poètic. The affections which spread beyond ourselves, and stretch far into futurity; the workings of mighty passions, which seem to arm the soul with an almost superhuman energy; the innocent and irrepressible joy of infancy; the bloom and buoyancy, and dazzling hopes of youth; the throbbings of the heart when it first wakes to love, and dreams of a happiness too vást for earth; woman, with her beauty, and grace, and gentleness, and fulness of feeling, and depth of affection, and her blushes of purity, and the tones and looks which only a móther's heart can inspire;-these are all poetical.

It is not true that the poet paints a life which does not exist. He only extracts and concentrates, as it were, life's ethereal èssence, arrests and condènses its volatile fràgrance, brings together its scattered béauties, and prolongs its more refined but evanèscent joys; and in this he does well; for it is good to feel that life is not wholly usurped by cares for subsistence and physical gratifications, but admits, in measures which may be indefinitely enlarged, sèntiments and delights worthy of a higher being.—Channing.

CAUSES OF WAR.

[To be marked for Inflections by the student.] What are sufficient causes of war let no man say, let no legislator say, until the question of war is directly and inevitably before him. Jurists may be permitted, with comparative safety, to pile tome upon tome of interminable disquisition upon the motives, reasons, and causes of just and unjust war. Metaphysicians may be suffered with impunity to spin the thread of their speculations until it is attenuated to a cobweb; but for a body created for the government of a great nation, and for the adjustment and protection of its infinitely diversified interests, it is worse than folly to speculate upon the causes of war, until the great question shall be presented for immediate action,-until they shall hold the united question of cause, motive, and present expediency, in the very palm of their hands. War is a tremendous evil. Come when it will, unless it shall come in the necessary defence of our national security, or of that honour under whose protection national security reposes, it will come too soon,-too soon for our national prosperity,-too soon for our individual happiness,-too soon for the frugal, industrious, and virtuous habits of our citizens,-too soon, perhaps, for our most precious institutions. The man who, for any cause, save the sacred cause of public security, which makes all wars defensive, the man who, for any cause but this, shall promote or compel this final and terrible resort, assumes a responsibility second to none, nay, transcendantly deeper and higher than any, which man can assume before his fellow-man, or in the presence of God, his Creator.-Binney.

FOUNDATION OF NATIONAL CHARACTER.

[To be marked for Inflections by the student.] Mental energy has been equally diffused by sterner levellers than ever marched in the van of a revolution,-the nature of man and the providence of God. Native character, strength, and quickness of mind, are not of the number of distinctions and accomplishments, that human institutions can monopolize within a city's walls. In quiet times, they remain and perish in the obscurity to which a false organization of society consigns them. In dangerous, convulsed, and trying times, they spring up in the fields, in the village hamlets, and on the mountain tops, and teach the surprised favourites of human law, that bright eyes, skilful hands, quick perceptions, firm purpose, and brave hearts, are not the exclusive appanage of

courts.

Our popular institutions are favourable to intellectual improvement, because their foundation is in dear nature. They do not consign the greater part of the social frame to torpidity and mortification. They send out a vital nerve to every member of the community, by which its talent and power, great or small, are brought into living conjunction and strong sympathy with the kindred intellect of the nation; and every impression on every part vibrates, with electric rapidity, through the whole. They encourage nature to perfect her

work; they make education, the soul's nutriment, cheap; they bring up remote and shrinking talent into the cheerful field of competition: in a thousand ways they provide an audience for lips, which nature has touched with persuasion; they put a lyre into the hands of genius; they bestow on all who deserve it, or seek it, the only patronage worth having, the only patronage that ever struck out a spark of "celestial fire," the patronage of fair opportunity.

teaching are devised; modes of instruction, choice of studies, This is a day of improved education; new systems o. adaptation of text-books, the whole machinery of means, have been brought, in our day, under severe revision. But were I to attempt to point out the most efficacious and comprehensive improvement in education, the engine, by which the greatest portion of mind could be brought and kept under cultivation, the discipline which would reach furthest, sink deepest, and cause the word of instruction not to spread over the surface, like an artificial hue, carefully laid on, but to penetrate to the heart and soul of its objects,-it would be popular institutions. Give the people an object in promoting education, and the best methods will infallibly be suggested by that instinctive ingenuity of our nature, which provides means of great and precious ends. Give the people an object in promoting education, and the worn hand of labour will be opened to the last farthing, that its children may enjoy means denied to itself.-E. Everett.

SUCCESS OF THE GOSPEL.

[To be marked for Inflections by the student.]

The assumption that the cause of Christianity to declining, is utterly gratuitous. We think it not difficult to prove that the distinctive principles we so much venerate, never swayed so powerful an influence over the destinies of the human race as at this very moment. Point us to those nations of the earth, to which moral and intellectual cultivation, inexhaustible resources, progress in arts, and sagacity in council, have assigned the highest rank in political importance; and you point us to nations whose religious opinions are most closely allied to those we cherish. Besides, when was there a period, since the days of the Apostles, in which so many converts have been made to these principles, as have been made, both from Christian and pagan nations, within the last five-andtwenty years? Never did the people of the saints of the Most High look so much like going forth in serious earnest, to take possession of the kingdom and dominion, and the greatness of the kingdom under the whole heaven, as at this very day.

reason to relax our exertions, for Jesus Christ has said, Preach But suppose the cause did seem declining, we should see no the gospel to every creature; and appearances, whether prosperous or adverse, alter not the obligation to obey a positive command of Almighty God. Again, suppose all that is affirmed were true. If it must be, let it be. Let the dark cloud of infidelity overspread Europe, cross the ocean, and cover our beloved land,-let nation after nation swerve from the faith,-let iniquity abound, and the love of many wax cold, even until there is on the face of this earth but one pure church of our Lord and Saviour Jesus Christ,-all we ask is, that we may be members of that one church. God grant that we may throw ourselves into this "Thermopyla of the moral universe."

But even then, we should have no fear that the church of God would be exterminated. We would call to remembrance the years of the right hand of the Most High. We would recollect there was once a time, when the whole church of Christ, not only could be, but actually was, gathered with one accord in one place. It was then that that place was shaken, as with a mighty rushing wind, and they were all filled with the Holy Ghost. That same day, three thousand were added to the Lord. Soon we hear, they have filled Jerusalem with their doctrine. The church has commenced her march:— Samaria has, with one accord, believed the gospel; Antioch has become obedient to the faith; the name of Christ has been proclaimed throughout Asia Minor; the temples of the gods, as though smitten by an invisible hand, are deserted; the citizens of Ephesus cry out in despair, Great is Diana of the Ephesians; licentious Corinth is purified by the preaching of

Christ crucified. Persecution puts forth her arm to arrest the spreading superstition; but the progress of the faith cannot be stayed. The church of God advances unhurt amidst racks and dungeons, persecutions and death; she has entered Italy, and appears before the wall of the Eternal City; idolatry falls prostrate at her approach; her ensign floats in triumph over the capitol; and she has placed upon her brow the diadem of the Caesars.-Wayland.

POWER OF THE SOUL.

[Marked for the application of Inflections.]

Life in itself, it life to all things gives:
For whatsoe'er it looks on, that thing lives,—
Becomes an acting being, ill or good;

And, grateful to its giyer, tenders food

For the Soul's health, or suffering change unblest, Pours poison down to rankle in the breast.

As is the man, e'en so it bears its párt,

And answers, thought to thought, and heart to heart.

Yès, man reduplicates himself. You see

In yonder lake, reflected rock and trèe,
Each leaf at rést, or quivering in the air,
Now résts, now stìrs, as if a breeze were there,
Sweeping the crystal dèpths. How perfect all!
And see those slender top-boughs rise and fall;
The double strips of silvery sand unite
Above, below, each grain distinct and bright.
-Thou bird, that seek'st thy food upon that bough,
Peck not alone; that bird below, as thòu,
Is bùsy after food, and happy too;

-They're gone! Both, pléased, away together flèw.

And see we thus sent up, rock, sand, and wood, Life, joy, and motion from the sleepy flood? The world, O man, is like that flood to thee: Turn where thou wilt, thyself in all things see Reflected back. As drives the blinding sand Round Egypt's piles, where'er thou tak'st thy stand, If that thy heart be barren, there will sweep The drifting waste, like waves along the deep, Fill up the vàle, and choke the laughing streams That ran by grass and brake, with dancing bèams, Sear the fresh woods, and from thy heavy eye Veil the wide-shifting glories of the sky, And one, still, sightless level make the earth, Like thy dull lonely, joyless Sòul,—a dèarth. The rill is tùneless to his ear who feels No harmony within; the south wind steals, As silent as unseen, amongst the leaves. Who has no inward beauty, none percèives, Though all around is beautiful. Nay, more,In nature's calmest hour he hears the roar Of winds and flinging wàves,-puts out the light, When high and angry passions meet in flight, And, his own spirit into túmult hurled, He makes a turmoil of a quiet world: The fiends of his own bosom, people air With kindred fiends, that hunt him to despair. Hates he his fellow-mén? Why, then he deems T'is hate for hate :-as hé, so èach one seems.

Sóul! fearful is thy power, which thus transforms All things into its likeness: heaves in storms The strong, proud séa, or lays it down to rest, Like the hushed infant on its mother's brèast,— Which gives each outward circumstance its húe, And shapes all others' acts and thoughts anèw, That so, they joy, or love, or hate impart, As joy, love, háte, holds rule within the heart.

HYMN OF NATURE.

R. H. Dana, sen.

[To be marked for Inflections.]

God of the earth's extended plains!
The dark green fields contented lie:
The mountains rise like holy towers,
Where man might commune with the sky:

The tall cliff challenges the storm
That lowers upon the vale below,
Where shaded fountains send their streams,
With joyous music in their flow.

God of the dark and heavy deep!

The waves lie sleeping on the sands,
Till the fierce trumpet of the storm
Hath summon'd up their thundering bands;
Then the white sails are dashed like foam,
Or hurry, trembling, o'er the seas,
Till, calm'd by Thee, the sinking gale
Serenely breathes, Depart in peace.

God of the forest's solemn shade!
The grandeur of the lonely tree,
That wrestles singly with the gale,
Lifts up admiring eyes to Thee:
But more majestic far they stand,

When, side by side, their ranks they form,
To wave on high their plumes of green,
And fight their battles with the storm.

God of the light and viewless air!

Where summer breezes sweetly flow, Or, gathering in their airy might,

The fierce and wintry tempests blow;
All,-from the evening's plaintive sigh,
That hardly lifts the drooping flower,
To the wild whirlwind's midnight cry,-
Breathe forth the language of Thy Power.
God of the fair and open sky!

How gloriously above us springs
The tented dome, of heavenly blue,
Suspended on the rainbow's rings !
Each brilliant star that sparkles through,
Each gilded cloud that wanders free
In evening's purple radiance, gives
The beauty of its praise to Thee.

W. B. O. Peabody.

LESSONS IN GREEK.-No. XLIII.

By JOHN R. BEARD, D.D.

VERBS IN μ, EXERCISES; REVIEW.

LET me here advise the student to spare no pains in order to acquire a complete familiarity with the model of the verbs and the remarks on the formations. If he passes on without that familiarity, he will be constantly at a loss, or, at any rate, be uncertain as to whether or not his view of a passage in Greek is correct. Inconceivable, too, will be the amount of the trouble he must take in order to ascertain by a sort of blind conjecture what part any verbal form he may meet with is; and without an exact knowledge of the part he will not be able to give the English equivalent. For want of grounding themselves thoroughly in the grammar, some persons, obtaining only a sort of half-knowledge of the language, are ever in difficulties, and find their task so hard that at last they give it up in despair; and others, who think they have made some proficiency, lose all they have gained, if for a comparatively short time they discontinue their Greek studies. Here in a special manner should the learner bear in mind that if a thing is worth doing at all, it is worth doing well. The labour may be severe and somewhat irksome, but far greater and far more disagreeable is the labour that falls on those who satisfy themselves with passing over the surface, and in an unwise eagerness for progress, constantly hasten to the new before the old is understood and mastered. I do not indeed suppose that any one will make the matter his own for ever by a first study. Again and again must the student retrace his steps; but let him not consider the first study accomplished until he feels that he has become well acquainted with the lesson actually before him. When once he has mastered a lesson, he may go on to the next, but while going forward let him always review the ground already trodden. At least one "front lesson” and