Imatges de pÓgina

that all fall down and worship her. The sonnets entitled "Old Church in an English Park," and "A Church in North Wales," are picturesque and thoughtful. In the sketch of "The English Martyr," there is a fine ode on the Passion.

"The Sun set in a fearful hour

The stars might well grow dim;
When this mortality had power,
So to o'ershadow HIM."

The Sabbath Sonnet, her latest work, dictated from her bed of death was a noble last strain for a Christian poetess.


"How many blessed groups, this hour are bending,
Through England's primrose meadow paths, their way
Toward spire and tower, 'midst shadowy elms ascending,
Whence the sweet chimes proclaim the hallow'd day.
The halls, from old heroic ages gray,

Pour their fair children forth; and hamlets low,
With whose thick orchard blooms the soft winds play,
Send out their inmates in a happy flow,
Like a free vernal stream. I may not tread
With them those pathways,-to the feverish bed
Of sickness bound;-yet, oh my God! I bless
Thy mercy, that with Sabbath peace hath fill'd
My chasten'd heart, and all its throbbings still'd
To one deep calm of lowliest thankfulness."

Our task is now briefly performed. We have asserted our argument, not that all poetry must be religious-but that the best poetry, and worthiest the name, that which enters into the nature of man, his passions, and affections, which represents his character must be essentially so. Let the poet then who would write for man, study to be taught of Heaven. Let the envy, malice and selfishness of his disposition, be supplanted by Christian charity. Let his life breathe the spirit of the New Testament. Let his inspiration be from Heaven.

ART. X.-Discoveries in Light and Vision, with a short Memoir, containing Discoveries in the Mental Faculties. New-York: G. and C. Carvill, and Co. 1836. 18mo. pp. 300.

ALMOST numberless are the opinions which in different ages of the world philosophers have held respecting the phenomena of light and vision. The Platonists and Stoics, taught that vision

was effected by the emission of rays out of the eyes; and Roger Bacon afterwards held the same opinion, giving the curious reason for it, that all things created, are designed to perform their own proper functions, by their own powers. The Epicureans held that vision is effected by the emanation of corporeal species, or images from objects; or a kind of atomical efiluvia, continually flying off from the intimate parts of its objects to the eye. The Peripatetics, held also that vision is produced by the reception of species, with this difference, however, that they believed the species to be incorporeal. Aristotle's account of vision, in his chapter de Aspectu, amounts at last, when freed from its cumbrous chains of species and images only to this, that objects must have some intermediate body, whereby to affect the organ of sight.


Of the modern philosophers, Descartes maintains, "that the sun passing the materia subtilis, with which the whole universe every where filled; the vibrations and pulses of that matter are reflected from objects, and communicated to the eye, and thence to the sensorium." Newton's theory is, "that vision is performed chiefly by the vibrations of a fine medium (which penetrates all bodies) excited in the bottom of the eye by the rays of light, and propagated through the capillaments of the optic nerve to the sensorium." The main point of difference between the doctrines of these two philosophers, upon the subject of vision, relates not so much to the mode in which impressions of outward objects are conveyed from the apparatus of the eye to the sensorium, as to the nature, qualities, and mode of development of light itself.

Though the general features of the two rival theories which originated with these two illustrious men, and were adopted, both in their own age, and subsequently, by the most distinguished philosophers on both sides, must be presumed to be familiar to most of our readers, we venture to recur to a few of the characteristic peculiarities of each.

Of the Newtonian or Corpuscular theory of light, the fundamental postulatum is, "that light consists of particles of matter, possessed of inertia, and endowed with attractive and repulsive forces, and projected or emitted from all luminous bodies with nearly the same velocity, about 200,000 miles per second." Other important assumptions are also requisite for the explicacation, by this theory, of the infinitely varied phenomena of light-and among them we mention as a second postulate, connected with vision-That these particles infringing on the retina, excite vision, the particles whose inertia is greatest producing the sensation of red, those of least inertia the sensation

of violet, and those in which it is intermediate, the intermediate colors."

These fundamental positions of the Corpuscular theory although now proposed as postulates or assumptions, seem to be legitimate deductions from the common and well known laws of reflection and refraction; and this theory has accordingly been generally received, and used for the solution of the phenomena of light.

The Huygenian or Undulatory theory, on the other hand, rests on this fundamental postulate, "that an excessively rare, subtle and elastic medium, or ether, fills all space, and pervades all material bodies, (less elastic in the interim of bodies,) and that when regular, vibratory motions of a proper kind, are propagated through the ether, and passing through our eyes, reach and agitate the nerves of our retina, they produce in us the sensation of light; the frequency of pulses determines the color, and the amplitude or extent of each wave or vibration, determines the intensity or brightness of the light." This theory, while it is less obviously deducible from the ordinary phenomena, rests on the strength of analogy with the laws of sound, and on its ready adaptation to explain and illustrate some few classes of phenomena, which are hardly, if at all, explicable by the corpuscular theory and it has the sanction of the weighty names of Descartes, Huygens, Hooke, Euler, and in later times, those of Young and Fresnel.

It is no part of our purpose to enter upon a discussion concerning the merits of either of these two important theories. Of the first it may be said, that it is perhaps the more simple and obvious, as resulting from the rectilinear progress of light in all uniform and hemogeneous media, and from the common laws of reflection and refraction, as we have remarked. While of the second, it may with almost triumphant force be asserted, that it readily meets the common laws of reflection, is reconcileable, though less readily with the laws of refraction, and above all, satisfactorily explains certain peculiar cases, where the other seems to fail. But whichever hypothesis be adopted, the mode of investigation, as to the facts and results to be arrived at, is in itself strictly geometrical, and so far indisputable. And it must be at once obvious, to all who have any acquaintance with geometry, that so long as the progress of light itself is rectilinear. and its changes of direction governed by certain fixed laws which observation has made known, that it can, in most cases, but little affect the result arrived at, whether the motion be one of particles actually moving onwards, or of vibrations directly propagated from one particle to another.

In the received doctrines of light, therefore, it must be apparent that all that rests upon observed facts and laws, carried out and applied by geometry, is beyond controversy; and such, most unquestionably, are all the ordinary productions of images by mirrors, and lenses and many kindred phenomena: on the contrary, all which belongs only to the regions of conjecture or speculation; as for instance, all questions relating to the forces which influence light in reflection or refraction, or to the modes in which light is essentially developed, &c.; is liable to be disputed by any body, and without the possibility of ever bringing the controversy to an absolute issue. In our analysis and examination, therefore, of the new treaties on light and vision, whose title stands at the head of this article, we propose a strict adherence to the acknowledged laws of investigation; reasoning only from established facts, and observed properties, and applying to these the certain aids of geometry.

The first and most important point in which this writer opposes the received doctrines of light, relates to the inverted image formed on the retina over the posterior surface of the chamber of the eye; and the author's proposition is thus announced:


Having always doubted the theory of seeing objects in an inverted position, I determined on testing its accuracy. The first moment it was in my power, I made the experiment, and the first eye that I examined, enabled me to detect the error under which we had so long labored." p. 1.

Then follows a description of the preparation of an eye, in the usual way, by removing the sclerotic coat, &c. from the hinder part of the eye, and a statement of the commonly observed fact of an inverted image on the posterior surface. But supposing this inversion to result from some derangement in the eye consequent on its removal from the socket, or from some other cause different from that usually ascribed, the author substituted an artificial pressure, similar to that of the socket, by holding it in the hand as if it were a tube, and pressing it all round equally yet gently."

"Instead of looking on the surface of the hole as is usually done when making this experiment, I looked through it; because, in the case of our own vision, I knew that the rays of light from an external object had to pass through the axis of the eye. At first nothing was seen, even the inverted candle had disappeared from the surface of the hole. Presently a bright light flashed across the animal's eye, and disappeared. As soon as I could keep my hand steady, the light again was visible; it proved to be a circular, and bright; and while it was thus stationary, I held a pin before the eye, with the head up, and to my surprise and pleasure, I found my previous opinions confirmed,

for the pin appeared exactly as I presented it to the eye of the animal. When I turned the pin upside down, it appeared upside down too! As soon as I lowered the eye, so that the central rays from the candle did not enter the axis of the animal's eye, then the candle again appeared on the surface of the little hole." p. 4, 5.

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On this first and single experiment, and the result as above announced, the writer most positively asserts, that the doctrine of the inverted image is "a gross delusion," and that the rationale heretofore adopted as explaining the fact that objects ap pear to us erect while their images are inverted, "will in a quarter of a century be the subject of amazement, ridicule, and merriment." We must remark upon these assertions, that they are, in our opinion, unsupported altogether by the facts of the case; and though we certainly feel a decided sentiment of respect for this bold, ingenious, and original writer, yet we could not but be surprised and amused at the degree and manner of the temerity, that could speak so scornfully of the results which observation and mathematical principles have been held to concur in establishing in regard to the doctrine of inverted images, and the ingenious, if not strictly true account which has been given of the way in which we see objects erect, while the images are inverted on the retina.

We consider it a fact too strongly supported by experiment, and too decidedly indicated by geometry, to be lightly yielded, that there is formed upon the back part of the chamber of the eye, an inverted image of every object within the range of vision; and, although the writer before us is so confident in asserting the contrary, we cannot, without more abundant evidence, and more satisfactory explanation, renounce the wellsustained doctrines of vision which now obtain. At the same time, we are fully willing to dispense in this case even-handed justice, and to give the author credit for some good, if not original suggestions, relative to the mode of action of some of the more delicate organs of sight. For full two centuries, have anatomists and philosophers been examining with great care the structure of the eye, and the mutual connections of its parts. These examinations have, indeed, been accompanied by various opinions as to the exact functions of each division of the organs of sight; yet, to this one conclusion, all who have closely examined, have uniformly come, viz. that the eye is justly considered a natural acromatic instrument, or camera obscura, in which pictures of external objects are exhibited as painted on the retina, or posterior surface of the chamber, by rays introduced through the aperture of the pupil. That the eye is constituted, and its parts arranged, with a special design

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