Изображения страниц
PDF
EPUB

How M. Chevalier could have so far misunderstood the purport of this criticism on Dr. Wollaston's method, as elsewhere indicated, we cannot conjecture. There is no doubt that Dr. Wollaston's figure, namely, fig. 1, of his plate, is quite incorrect, as M. Chevalier states; but the criticism was not founded on the erroneous figure, as he supposed, but on the description of the apparatus in the text; and we have no doubt that M. Chevalier, should this notice meet his eye, will acknowledge that he has entirely misapprehended Dr. Wollaston's method of illumination, and has not

Phil. Transactions for that year. His object was | Dr. Wollaston illuminated his objects, not with to get rid of unnecessary light which impeded rays of light which were actually converged upon vision, and not to remove the evils arising from the object, but with rays diverging from a point diffraction. Dr. Wollaston never once mentions between the object and the illuminating lens; and diffraction, or any other cause, but that of super- it is obvious, from his recommendation to use at fluous light; as the origin of imperfect vision aris-night a common bull's-eye lanthorn, that he had no ing from the usual modes of illumination. He idea whatever of the necessity of bringing the rays was not aware, indeed, that the diffraction of the to a focus upon the object with such accuracy that light used for illumination was the evil to be cor- they should again radiate from it as if it were rected, and he has accordingly not corrected it by self-luminous. His object seems to have been his apparatus. "In the illumination of micro-solely to get a distinct and equally illuminated disc scopic objects," says he, "whatever light is cor- of light of no greater diameter than what was rected and brought to the eye beyond that which is necessary for seeing the object; for no illumination fully commanded by the object-glasses, tends rather of the smallest value can be obtained unless by to impede than to assist distinct vision. My lenses free from chromatic and spherical aberration, endeavor has been to collect as much of the admit- or of such a short focus, from the 20th to the 80th ted light as can be done by simple means to a focus part of an inch, that the effects of aberration become in the same place as the object to be examined. almost inappreciable. For this purpose I have used with success a plane mirror to direct the light, and a plano-convex lens to collect it." In describing the apparatus itself, he says that this "plano-convex lens, or one properly crossed, (that is, its radius 1-6 or 6-1,) to have the least aberration, should be about three quarters of an inch focus, having its plane side next the object to be viewed, and at the bottom is a circular perforation A, of about three tenths of an inch diameter, for limiting the light reflected from the plane mirror, and which is to be brought to a focus at a, (the place of the object,) giving a neat image of the perforation A, at the distance of about 8-appreciated the method of Sir David Brewster, 10ths of an inch from the plano-convex lens, and in the same plane as the object which is to be examined. For the perfect performance of this microscope, Dr. Wollaston adds, it is necessary that the axis of the lenses, and the centre of the perforation should be in the same right line. This may be known by the image of the perforation being illuminated throughout its whole extent, and having its whole circumference equally well defined. For illumination at night, a common bull's-eye lanthorn may be used with great advantage." In the appendix to his paper, Dr. Wollaston gives the following measurements and unequivocal directions for the adjustment of his illuminating lens. "The position of the lens may be varied so as to bring the image of the perforation* into the same plane with the object to be viewed. * Supposing the plano-convex lens (the illuminating lens) to be placed at its proper distance from the stage, the image of the perforation may be readily brought into the same plane with the object, by fixing temporarily a small wire across the perforation with a bit of wax, viewing any object placed upon a piece of glass upon the stage of the microscope, and varying the distance of the perforation from the lens by screwing its tube until the image of the wire is seen distinctly at the same time with the object upon the piece of glass." Hence it is demonstrable that

*That is the conjugate focus of the perforation, considered as a circular object, from which rays diverge-not the conjugate focus of the rays which pass through the perforation.

which he supposed it to resemble. To make light radiate from an object seen in a microscope of any reasonable magnifying power, by means of a planoconvex lens, or a properly crossed lens of 3-4ths of an inch focus, and 3-10ths of an inch in diameter, would be as absurd as to expect to see the satellites of Saturn through an opera-glass; and still more absurd is it when the object is illuminated by rays whose conjugate focus is the centre of a perforation within two or three inches of the lens, instead of being at very great or an infinite distance.

It is in vain to expect from the microscope that scrutiny of minute objects which it is fitted to give till it is furnished with an illuminating apparatus as perfect as its magnifying apparatus—a combination of powers which requires the microscope to be fitted up in a manner quite different from what it is at present.

The fourth treatise placed at the head of this notice contains some excellent and useful observations on simple and compound microscopes. The pancratic microscope, which it is the principal object of the treatise to describe, differs from others, in so far as it admits a successive increase of magnifying power without changing either the eye-piece or object-glass. This is effected by using an eye-piece consisting of four lenses, two of which next the eye can be separated by a drawtube from the other two lenses. In a report on Professor Fischer's microscope by a committee of

*See Edinburgh Journal of Science, New Series, No. XI., p. 83, Jan. 1832.

COMPOUND ACHROMATIC MICROSCOPE-MAN'S LOVE-WOMAN'S LOve.

the Imperial Academy of Sciences at St. Petersburg, the merit of this invention, as applied to telescopes, is ascribed to Sir David Brewster, who took out a patent for it in 1812, and published an account of it in his treatise on New Philosophical Instruments. The report speaks favorably of its application to the microscope, the credit of which belongs to Mr. Fischer, and we have no doubt that for many purposes such an instrument would be useful; but as there is only one position of the two parts of the eye-piece in which the achromatism is most perfect, a variation of magnifying power would be better obtained by the use of different eye-pieces, as in our best microscopes.

From the N. Y. Literary World.

A COMPOUND ACHROMATIC MICROSCOPE, MADE
BY AN AMERICAN ARTIST.

We have lately had the pleasure of examining a microscope of high power, with some account of which our readers may be interested, both for the actual merit of the instrument, and for the circumstances under which it was made.

Mr. Charles Spencer, of Canastota, in this state, visited our city about a year ago, and had, through the kindness of a professor in one of our schools of medicine, an opportunity of examining a microscope made by Chevalier, of Paris, under the orders of the celebrated Jussieu, of the Garden of Plants. Mr. Spencer had never seen one of these instruments before, but, after careful examination, he surprised the professor, by remarking, with all the simplest confidence imaginable: I could make a better microscope than that." The person to whom this boast was made, often, during the next six months, amused his friends with the Yankee presumption of the backwoods artist, who so confidently claimed superiority over the first optician in France. The jest lasted but six months, however, for, at the end of that time, the professor was invited to examine two lenses, one of high power, made by Mr. Spen

cer.

66

To his unbounded astonishment, they proved to be of the highest order of excellence, and, as a reward to native ingenuity, he ordered a microscope from Spencer, to be modelled after those of Chevalier, and of course as much better as the native could make it. This instrument has just been completed and placed in the hands of the owner.

It has already been examined by Professor Bailey, of West Point, who has no superior as a microscopist in this country; by Prof. Torrey, who had long been in the habit of using one of Chevalier's best instruments; by Prof. Clark, Dr. Gilman, and others of our savans, who all unite in pronouncing it excellent. Prof. Bailey says it is "decidedly superior to Chevalier's," and adds, that he could do all with it that he could with the Lowell instrument at Boston.

Thus has one of our countrymen, self-taught, and almost without experience, (for Spencer has made but very few instruments, and not one on the model of this,) taken his place beside the oldest and most experienced opticians of Europe. We are happy to hear that he is already reaping the fruit of his labors. Prof. Henry, of the Smithsonian Institute, has ordered a large instrument, on which, we doubt not, all his talents will be displayed-Dr. Clark two-and others, we doubt not, will follow. No man need hereafter import a foreign instrument. We can add these to the number of our domestic manufactures.

MAN'S LOVE.

Он! Fanny, do not sigh for me,-
I shall not sigh for you;

With heart unfettered, light and free,
I smile a last adieu.

231

Though strewed with flowers the sportive hours
With Fanny that flew by,

I could not stay another day,
For India's gold-not I!—
For still my bounding heart is free,
And longs for something new;
Then, Fanny, do not sigh for me,—
I shall not sigh for you!

The bird that hath not built its nest,
Is not more free than I;
The butterfly is not more blest,-
From sweet to sweet I fly.

My pathway lies through sparkling eyes,
I count them o'er and o'er;
Each dawning light appears more bright
Than that which shone before!
For ah! to love them all I'm free,
(I'll use that freedom too!)
Then, Fanny, do not sigh for me,-
I shall not sigh for you!

Sharpe's Magazine.

WOMAN'S LOVE.

“THY home is not so bright, Ladye,
As it was wont to be;-

Thine eyes have lost their light, Ladye,
Thy laugh its ringing glee.
Thy step is sad and slow,-

Thy faltering accents fail;
Alas! that tears should flow

Down cheeks so young and pale!
Thou wert not once so sad and strange ;-
Oh! what has wrought this wondrous change?"

"Mine eyes are like the moon, Pilgrim,

They shone with borrowed light;
My cheek, like flowers of noon, Pilgrim,
Grows pale with coming night.
My voice is like the bird

That greets the op'ning day;
My laugh is only heard

When this poor heart is gay:
Oh! when the sun has left the sky,
The earth is dark-and so am I!"

"The sun is shining bright, Ladye,

Down from the summer skies;
The flowers that sleep at night, Ladye,
Now ope their smiling eyes.
The birds are singing now,
With free exulting voice;
Nature is glad-and thou,-

Why dost not thou rejoice?

Look up, and greet the sun's bright beam-
Feel that of night thou dost but dream."

"That dream is in my heart, Pilgrim,
It lieth there so deep,
It never will depart, Pilgrim,
Awake, nor yet in sleep:
A dream of severed ties,

Of love so fond-so vain ;
Of words, and smiles, and sighs,
That will not come again!
My sun, alas! was not in heaven :
Its light from human eyes was given !"

THE MILITARY CLASS.

THE Philadelphia Public Ledger thus states a doctrine which seems to be growing very fast:

Some of the journals express apprehensions about the creation of a military class, or standing army, as ultimately fatal to our republic. They refer to the wishes expressed by the most intelligent of the Mexican population, for the continued occupation of their country by our armies, to protect them against their own, as something quite significant of the future to ourselves. They ask what we should think, if compelled to seek the protection of foreign bayonets against our own armies; and they say that this will come, if we create a numerous military class.

Though going as far as any journal in hostility to standing armies, we do not participate in these apprehensions. We regard the annihilation of Mexican nationality, the annexation of Mexico to our own republic, as a measure which will ultimately remove all necessity for standing armies. The standing armies of continental Europe are a necessity of its national subdivision. These European nations, separated by merely conventional, not natural boundaries, must fence against each other with standing armies. And as popular governments and standing armies are entirely incompatible, their governments must be despotisms of some kind. We despair of free governments in Continental Europe, till its standing armies disappear, and we despair of this disappearance till the European nations are incorporated in some confederacy. Universal empire, under some federal system, has been a favorite project with some of its great men, who saw in advance of their age, and especially with Henry IV. of France. But the attempts at universal empire made by some of its great military geniuses, and especially Napoleon, did not look beyond the aggrandizement of himself and his family. Why, then, are free governments a moral impossibility in Continental Europe? The superficial reply, "Because European nations have standing armies." But the far-seeing reply, "Because it is subdivided into different nations, which must fence against each other with standing armies." By removing the standing armies, we shall remove the despotism. Granted. But to remove the standing armies, we must first remove the national subdivision.

Applying this doctrine to our own continent, we say that with neighbor nations to fence against, we republicans must have standing armies. But with a confederacy covering the whole continent, and nothing but the continent, we shall have no national neighbors, and therefore nothing against which to raise military fences. Even England, an European nation, illustrates this doctrine, when contrasted with Continental Europe, and also when contrasted with our own country. England, safe against Continental Europe by the natural barrier of the ocean, needs no standing armies at home. When invasion is threatened, her intelligent and energetic population become a standing army for the crisis.

She once had a feudal standing army to repel the Scots, while the Scots had one to repel the English. The union of the two neighbors removed this necessity; and now, standing armies to protect one against the other, would be as useless as they would between New York and Pennsylvania. So far, England and Scotland are like the United States. But England has numerous conquered dependencies, which she must protect against other nations, or keep in order towards herself, by standing armies.

Here she has something like continental subdivision, and consequently something to fence against.

Then to remove all necessity for standing armies, we must have no neighbors to fence against, or, in other words, we must extend our confederacy over the continent. In other words, we must conquer, absorb Mexico. But these journals object to the annihilation of a sister republic. Do they believe that this sister republic will ever be our ally and coöperator against Europe? A rival, hostile race, they will be our enemies under any circumstances, and therefore impose upon us the necessity of building the military fence. But will Mexico continue a republic? By no means. The European governments will impose monarchy upon it, and make monarchy an instrument of its renovation, till it becomes, like France or England, a powerful nation, with large fleets and armies, a rich aristocracy and a poor people. And they will do this to force us into standing armies against Mexico. They know that our prosperity and power flow from our republicanism. They would dry up its source; and they know that this republicanism must soon wither under an expensive military government, and that an expensive military government will become a necessity with us, when Mexico is made a powerful military monarchy.

But the journals tell us that this conquest of Mexico renders large armies necessary, and that when the conquest is completed we cannot disband the armies. Indeed! Congress have constitutional power enough for it, and the people will have the will. That a hundred thousand soldiers should be formidable to twenty millions of the most military people in the world, is a proposition that we can hardly meet seriously. Would Pennsylvania be intimidated by her two regiments? Were they ten, the state has a few more left of the same sort, competent to extinguish them on any day, in voting or fighting.

But in taking Mexico we shall take an Ireland. Yes, if we are unwise enough to follow the English example, and keep it a distinct and hostile dependency, for the benefit of an aristocracy at home. But we shall avoid all this, and make it another Louisiana, by pursuing the Russian policy of introducing our own laws, language, and customs, and thus rendering Mexico Anglo-American.

By extending our confederacy over the continent, the whole continent, and nothing but the continent, we shall ultimately remove all of a military class, and shall thus preserve our liberties.

From the Journal of Commerce.

THE BENEFACTOR OF AN EMPIRE.

WHILE Scores of worthless, if not injurious, volumes, are, in this book-making age, sent out every month into the community, it is truly gratifying to meet with such a work as "The Chinese Empire," by Williams, just issued from the press of Wiley & Putnam. From the great amount of valuable information contained in these two octavo volumes, the following facts are selected respecting the labors of Dr. Morrison, the first Protestant missionary to China.

He received his appointment from the London Missionary Society in 1807, and proceeded immediately to Canton, by way of New York; the East India Company at that time refusing a passage in their ships to all missionaries, either to India or China. During the first year he lived in a room of the factory of Messrs. Milner & Bull, of New York, devoting his whole time to the study of the language. China was then a sealed country to missionaries.

the whole was completed in six quarto volumes, in 1823, at an expense of £12,000.

While the Dictionary was going through the press, the Old Testament was progressing by the joint labors of Dr. Morrison and Mr. Milne, and in Nov., 1818, the entire Bible was published. In the mean time Dr. Morrison had also published, both in Chinese and English, a tract on Redemption, a translation of the Assembly's Catechism and Liturgy of the Church of England, a Synopsis of the Old Testament History, a hymn-book, a Tour of the World, and a few essays on religious subjects. Of these several works nearly thirty thousand copies were distributed. In 1815 he published dialogues in English and Chinese, and a volume a Chinese grammar; and also a small volume of entitled View of China in 1817.

Dr. Morrison accompanied Lord Amherst to Peking in 1816, as interpreter to the embassy; the return journey through the country affording him opportunity of collecting much valuable infor

mation.

In 1824, Mrs. M. having died three years preIn consequence of commercial difficulties in vious, Dr. Morrison returned to England, where 1808, he was obliged, with all British subjects, to he was honorably received, presented to his leave Canton and repair to Macao. There, in majesty George IV., and warmly encouraged by 1809, he accepted the appointment of translator to all interested in the advancement of religion and the East India Company; an office which furnished learning. He published a volume of sermons him all necessary security, so that he could prose- while in England, formed a second matrimonial cute his work with diligence and confidence; at the connection, and returned to China in 1826. From same time his salary was sufficient for the support this time till his death in 1834, though chiefly of his family, and enabled him to proceed in his occupied by his duties as translator to the Company, studies, with but little expense to the society. he published a Vocabulary of the Canton Dialect, The translation of the Scriptures, and the printing in two volumes, for the use of foreign residents and publishing of his numerous works, says the and seamen in their intercourse with the Chinese; author, could hardly have been carried on, at that also a Miscellany of useful information, in four time, without the countenance and aid of that pow-volumes, and three or four smaller works; a erful and wealthy body. of the Psalter and Liturgy, and a volume of hymns Selection of Scriptural Lessons, a second edition and prayers.

In 1810 the Acts of the Apostles were issued by Dr. Morrison-the first portion of the Bible printed in Chinese-followed in 1812 by the Gospel of Luke; on each of which occasions the B. and F. Bible Society granted five hundred pounds to assist in the prosecution of the work. In 1814 the whole New Testament was published, about half of it having been translated entirely by Dr. M., and the remainder revised by him from a manuscript found in the British Museum.

The leading objects of the society, in sending Dr. Morrison to China, were the translation of the

Bible and the preparation of a Dictionary, with such additional labors in preaching, teaching, and writing tracts, as he found leisure and opportunity to perform.

The compilation of the Dictionary progressed so well, that in the same year Mr. Elphinstone, Sir George Staunton, and a few others of the E. I. Company's establishment in China, interested themselves in getting it printed, and for this purpose applied to the Court of Directors in London, who, sensible of the importance of the undertaking, responded on the most liberal scale, and sent out a printer and a printing office. The first volume, of near a thousand pages, was issued in 1817, and

He died at the age of 52, having spent twentyseven years of missionary labor in China, and most of that time alone. After all his toil, and faith, and prayer, he saw only three or four converts, no churches, schools, or public congregations, yet he was not discouraged. In his last letter he says, "I wait patiently the events to be The Lord reigneth." Few men have ever accomdeveloped in the course of Divine Providence. plished so great an amount of labor, or, as

a

pioneer, done so much to prepare the way for evangelizing millions of the human family.

DOG-CHASE.

WE beg to suggest that when provision is made by congress for taking the next census of 1850, it shall be made the duty of the United States marshals and their deputies to take down the number of the dogs in the country; which, notwithstanding the extensive interest of the subject, is one on which the universal American people, who know everything, know nothing. Who can tell how many dogs we have in the United States-or who

can guess? Fifteen millions of horned cattle, the various points of his visitation, as to raise a twenty millions of sheep, thirty millions of hogs; doubt whether one dog, however ferocious and these are ascertained numbers-but how are we to determined, could accomplish so large an amount deduce from them the canine population? The of mischief. One morning the owner of a fine Farmers' Library, of this month, speaking of the flock would ascertain that several of his choicest late Nathaniel Macon, says, he told the editor "he sheep were lying killed in his fold, and himself would not live where there was a law against some thirty or forty pounds the poorer; and the dogs," and declared that "each of his negroes next, a farmer so many miles distant as to warrant kept one, and that he kept thirteen." This might his fancying himself out of harm's way, would give us the means of striking some average for the discover himself in a similar position, from the dogs of the southern states; but the object is to totally unexpected visit of this ruthless destroyer. find the numbers for the whole country. To such a height had the ravages of the brute proceeded during an entire month, that the “country side" literally rose in arms" against him. Nearly a hundred sheep had he torn the throats of, and though seen now and then at a distance, he never would allow a single person to come within gun-shot range of him. He was understood to be dark-colored, of unusual size, and swift of foot; but that was all, and doubts were entertained as to whether it really was a dog or not, many being inclined to believe, from the description given of it, that it might be some wild beast escaped from a travelling menagerie.

66

We think it would be a very moderate basis of computation to allow one dog to every family in the United States. This would give us, in round numbers, about five millions of dogs; each of which, living on garbage and offul, consumes annually the food that would raise a pig, worth one dollar. The cost of feeding our dogs in the United States is, therefore, $5,000,000 a year, and their existence is a dead loss to the nation, annually, of that amount. But how many millions of dollars are lost by the sheep destroyed every year by dogs? That is an item which no man can compute, until congress shall choose to direct the attention of the Certain it is that its appearance, in a country so census-takers to the subject. It will, undoubtedly, thinly populated, and so quiet and retired, and the turn out, when ascertained, to be a great and pro- destruction that attended its path, gave rise to many digious loss. Few persons are aware of the havoc stories more creditable to the imagination than to which a single bad dog can make among a flock the judgment of the narrators. The excitement of sheep in a few moments. We have been told created naturally increased with every further acthat Major Raybold, of Delaware, computes his count of the animal's deadly visits; and at length individual losses in this way, notwithstanding every the farmers of the district felt themselves compelled care to prevent them by shepherds, watch-dogs to set watches over their flocks every night; or to and poison, at upwards of three thousand dollars; house every sheep, at whatever inconvenience, beand we learn that one of his enterprising sons lost, fore dusk. Those who know the country of which last week, in a single night and by a single dog, we speak, the perfect security which is felt as to eighteen or twenty sheep of an improved stock, any attacks on property, and the great difficulty worth ten dollars a head. We have cut from our the farmers generally would have in obtaining asEnglish files an account of a canine " sheep-sistance to keep night watches, or in finding room stealer," who seems, for a time, to have threat- in their outbuildings at this time of the year for ened the ruin of all the sheep farmers near Preston. anything like a flock of sheep, however small, It is clear that "man's most faithful friend" is will readily understand the desire which was unirather a costly one; and when we add the danger versally felt to rid the country of a visitor who and loss of human life from hydrophobia, one is caused so much annoyance, anxiety and fear. In more disposed than ever to ask why the paternal the early part of last week the farmers of the counattention of the government should not be directed try turned out far and near, to the number of uptowards the enumeration and general statistics of wards of a hundred, armed with guns, pitchforks, this branch and class of our animal population.- &c., and completely scoured the district in search American & Gazette. of their enemy, but without effect. On Saturday CHASE OF A SHEEP-SLAYER.-Extraordinary night week it was found that he had killed twelve losses have recently been suffered by the farmers sheep, at Beacon-fell-side; and on the Sunday in the district north of Preston, from the remarka- following three or four hundred persons were on ble sheep-killing propensities of a large and fierce the hunt for the destroyer. In the course of the dog, which roamed over the country at night, day, Mr. Logan, of Barton, got a distant shot at slaughtering sheep in every direction, and escap- a large dog by the side of Barton mill, supposed ing by some unaccountable means the numerous to be the one all were looking for, but the animal snares which were set to compass its capture, dead escaped unhurt. That night he killed fifteen sheep or alive. Night after night did this mysterious at Catterall-hall. On Wednesday, at day break, brute pursue his course, creating alarm in every the brute was seen in the act of tearing a sheep's direction, and seemingly defying any attempt to throat out at Woolfell's-mill, having five others check the mischief he was making. No farmer's lying dead about him. The cry was immediately flock, in the wide district he selected as the scene raised; all within hearing turned out, with such of his ravages, was safe from his attack; while weapons as could be seized in the hurry and exhe occasionally placed so great a distance between citement of the moment; and the start was com

« ПредыдущаяПродолжить »