Imatges de pàgina
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me now attend to another circumstance, no less
admirable than the preceding, and that is, the
distinct impression which I have of the shape,
colour, and motion, of the multiplicity of objects
I am now contemplating, and the small space
within which their images are depicted at the
bottom of my eye. Could a painter, after a long
series of ingenious efforts, delineate the extensive
landscape now before me, on a piece of paper not
exceeding the size of a silver sixpence, so that
every object might be distinctly seen, in its pro-
per shape and colour, as it now appears when I
survey the scene around me, he would be incom-
parably superior to all the masters of his art that
ever went before him. This effect, which far
transcends the utmost efforts of human genius,
is accomplished in a moment, in millions of in-
stances, by the hand of nature, or, in other words,
by "the finger of God." All the objects I am now
surveying, comprehending an extent of a thousand
square miles, are accurately delineated in the bot-
tom of my eye, on a space less than half an inch
in diameter. How delicate, then, must be the
strokes of that Divine pencil, which has formed
such a picture! I turn my eyes to the castle of
Edinburgh, which appears one of the most con-
spicuous objects in my field of view. Supposing
that portion of it which strikes my eye to be 500
feet long, and 90 in height, I find, by calculation,
that it occupies only the six hundred thousandth
part of the whole landscape, and, consequently,
fills in my eye no more than the twelve hundred
thousandth part of an inch. I next direct my
eye towards the Frith of Forth, and perceive a
steamboat sailing between Queensferry and New.
haven, I distinctly trace its motion for the space
of 40 minutes, at the end of which it reaches the
chain pier at Newhaven, having passed over a
space of five miles in length, which is but the
eighth part of the lineal extent of the landscape
in that direction; and, consequently, occupies,
in the picture formed on my retina, a lineal space
of only one-sixteenth of an inch in extent. And,
if the boat be reckoned about 88 feet in length,
its image is only the three hundredth part of this
extent; and of course, fills a space in the eye of
only the four thousand eight hundredth part of a
lineal inch. Yet, my perception of the motion
of the vessel could be produced only by a corres-
ponding motion of its image in my eye; that is,
by the gradual motion of a point one 4,800th of
an inch in diameter, over a space one-sixteenth
of an inch in length. How inconceiveably fine
and accurate, then, must be the impression of
those strokes which the rays of light, from visible
objects, produce on the retina of the eye! The
mind is lost in wonder when it attempts to trace
so exquisite and admirable an effect.

I take a reflecting telescope, and, through it, view some of the distant parts of the landscape. My wonder is still increased, when I consider the new direction into which the rays of light are

bent-the crossings and recrossings, and refrac tions, and reflections, that take place between the mirrors and the lenses of the instrument, and the successive images that are formed-so that, instead of a scene of confusion, which, previous to experience, might have been expected from the numerous additional bendings and intersections of the rays-I now perceive hun dreds of objects, with the most perfect distinctwhich were before invisible. Rays of light from distant and minute objects, which a moment before made no sensible impression on my eye, being collected and variously modified by the telescope, now paint a vivid representation of their objects, in their true figures, colours, and positions.

ness,

From a consideration of the innumerable modifications of the rays of light, and of the immense variety of effects they produce in every region of the earth-I am led to investigate what proportion of the solar light falls upon our globe, in order to produce so diversified a scene of sublimity and beauty. Supposing the sun's rays to be chiefly confined, in their effects, within the limits of the planetary system, since they diverge in every direction, they must fill a cubical space of 3,600,000,000 miles in diameter; which, consequently, will contain about 24,000,000,000,000,000,000,000,000,000 cubical miles; so that an eye, placed in any point of this vast space, would receive a distinct impression from the solar rays. The solidity of the earth is about 264,000,000,000 cubical miles, and, therefore, it receives only the 50,000,000,000,000,000th part of the light which fills the sphere of the solar system. So that the light which cheers all the inhabitants of the world, and unveils such a variety of beautiful and magnificent objects, is nothing more than a single stream of celestial radiance out of ninety thousand billions of similar streams which the great source of light is every moment diffusing throughout the surrounding worlds. But the solar rays are not confined within the bounds of the planetary system; their influence extends, in every direction, as far as the nearest stars, filling a cubical space at least 40,000,000,000,000 miles in diameter, and which contains 33,500,000,000,000,000,000,000,000,000,000,000,000,000, or thirty-three thousand, five hundred sextillions of cubical miles. And, were we to institute comparisons and calculations, with respect to the possible variety of effects they might produce throughout this immense region, whole pages might be filled with figures, cyphers, and computations. We might compute how many globes similar to the earth, or any of the larger planets, might be contained within this vast space, allowing several hundreds of cubical miles of empty space around each globe

how many myriads of refractions and reflec tions the rays of light would suffer, in regard to the peculiar objects connected with every one

of these globes-how many eyes of sentient beings might be affected by the diversities of colour, shape, and motion, which would thus be produced-and what a variety of shades of light and colour, and what a diversity of scenery, would be produced, according to the distances of the respective globes from the central luminary. After what we have just now stated, however, we may rest satisfied with joining in the pious exclamation of one who had just finished a devout survey of the structure of the human frame: "Marvellous are thy works, and that my soul knoweth right well. How precious are thy thoughts unto me, O God!" (or, as the words might be rendered,) "How precious are thy wonderful contrivances concerning me, O God! how great is the sum of them! IfI should count them, they are more in number than the sand." In what direction soever I turn mine eyes, what ever portion of thy works I investigate, "I am still with thee."* Thine infinity and unsearchable wisdom are impressed on every object, so that I feel myself every moment encompassed by thine immensity, and am irresistibly led to wonder and adore.

I shall now conclude these reflections on vision, with two or three additional remarks. It is worthy of notice, in the first place, that the eye has the power of adapting itself to objects placed at different distances. By means of some delicate pieces of mechanism, not hitherto satisfactorily explained, it can perceive, with distinctness, a large object, at the distance of six miles, and the next moment it can adjust itself to the distinct perception of an object at the distance of six inches; so that it acts the part both of a telescope and a microscope, and can be instantaneously adjusted to perform either as the one instrument or as the other. This necessarily supposes a corresponding alteration in the state of the organ, every time we lift our eye from a near, to look at a distant object. Either the cornea is somewhat flattened, or the crystalline humour is pushed backwards, or both these changes, in combination with others, may concur in causing the rays from distant objects to unite exactly on the retina, without which distinct vision cannot be produced. This contrivance, in whatever kind of mechanism it may consist, is one which art would vainly attempt to imitate. We can see objects that are near us, with a microscope, and those that are distant, with a telescope but we would in vain attempt to see distant objects with the former, or those that are only a few inches from us with the latter, without a variety of changes being made in the apertures and positions of the glasses belonging to the respective instruments. In this respect, therefore, as well as in every other, the eye is an optical instrument, incomparably superior to any

• Psalm cxxxix. 14, 17, 18.

instrument or imitation that art can produce; and, were it not for the peculiar property now described, it would be almost unfit for the purpose of vision, notwithstanding all the other delicate contrivances which enter into its construction. If it were adjusted only for the distinct perception of distant objects, every object within the limits of an ordinary apartment would appear a mass of confusion; and were it adjusted solely for viewing objects within the limits of a few feet or inches, the glories of the heavens, and the beautiful landscape of the earth, would be veiled from our sight as if they were enveloped in a mist.

Another circumstance worthy of attention, is, the power which the pupil of the eye possesses of contracting or enlarging the aperture or hole through which the light is admitted. When the light is too weak, the pupil is enlarged; when it is too strong, it is again contracted. Accordingly, we find, that when we enter a darksome apartment, though, at first, nothing can be accurately distinguished, yet, in the course of a minute or two, when the pupil has had time to dilate, we can perceive most objects with considerable distinctness. And, on the other hand, when we pass from a dark room to an apartment lighted up with a number of lustres, we feel uneasy at the sudden glare, till the pupil has contracted itself, and excluded a portion of the superfluous rays. Were it not for this property, we should for the most part either be surrounded with a disagreeable gloom or oppressed with an excessive splendour. It is for this reason, that we are unable to look upon the sun without being dazzled, and are under the necessity of closing the eyelids, or of turning away the head, when a strong light suddenly succeeds to darkness.

Again, it may not be improper to observe, how wisely the Author of nature has fixed the distance at which we ordinarily see near objects most distinctly. This distance is generally from five to eight inches from the eye. But had the eye been formed for distinct vision at the distance of only one inch, the object would have obstructed the light, and room would have been wanting for the performance of many necessary operations, which require the hand to intervene between the eye and the object. And had the limits of distinct vision for near objects been beyond two or three feet, sufficient light would not have been afforded for the inspection of minute objects, and we could neither have written a letter, nor have read a book, with the same convenience and ease we are now enabled to do.

From the preceding descriptions and remarks, it will evidently appear, with what admirable skill the different parts of the organs of vision are constructed, and how nicely they are adapted to the several ends they were intended to subserve. Were any one of these parts wanting, or obstruct ed in its functions, vision would either be impeded, or rendered painful and distressing, or

completely destroyed. If any of the humours of the eye were wanting-if they were less transparent-if they were of a different refractive power -or if they were of a greater or less convexity than they now are, however minute the altera, tion might be, vision would inevitably be obstucted, and every object would appear confused and indistinct. If the retina, on which the images of objects are painted, were flat, instead of being concave, while objects in the middle of the view appeared distinct, every object towards the sides would appear dim and confused. If the cornea were as opaque as the sclerotica, to which it is joined, or if the retina were not connected with the optic nerve, no visible object could possibly be perceived. If one of the six muscles of the eye were wanting, or impeded in its functions, we could not turn it to the right; if a second were deficient, we could not turn it to the left; if a third, we could not lift it upwards; if a fourth, we could not move it downwards; and if it were deprived of the other two muscles, it would be apt to roll about in frightful contortions. If the eyes were placed in any other part of the body than the head-if they were much more promi nent than they now are-if they were not surrounded by the bony socket in which they are lodged-and if they were not frequently covered by the eyelid they would be exposed to a thousand accidents from which they are now protected. If they wanted moisture, and if they were not frequently wiped by the eyelids, they would become less transparent, and more liable to be inflamed; and if they were not sheltered by the eyebrows, the sweat and moisture of the forehead would frequently annoy them. Were the light which acts upon them devoid of colour-were it not reflected from objects in every directionwere its motion less swift, or its particles much larger than they now are-in short, were any one circumstance connected with the structure of this organ, and with the modification of the rays of light, materially different from its present arrangement, we should either be subjected to the hourly recurrence of a thousand painful sensations, or be altogether deprived of the entertainments of vision.

How admirable an organ, then, is the eye, and how nicely adapted to unveil to our view the glories of the universe! Without the application of any skill or laborious efforts, on our part, it turns in every direction, transports us to every surrounding object, depicts the nicest shades and colours on its delicate membranes, and

"Takes in, at once, the landscape of the world,
At a small inlet, which a grain might close,
And half creates the wond'rous world we sce."
Young

-How strikingly does it display, in every part
of its structure and adaptations, the marks of
benevolent design, and of Infinite Intelligence!
However common it is to open our eyes, and to

behold, in an instant, the beauties of an extensive landscape, and however little we may be so customed to admire this wonderful effect.—there is not a doctrine in Religion, nor a fact recorded in Revelation, more mysterious and incompre hensible. An excellent French writer has wel observed-"The sight of a tree and of the sum which God shows me, is as real and as imme diate a revelation as that which led Moses to wards the burning bush. The only difference between both these actions of God on Moses ard me, is, that the first is out of the common order and economy; whereas the other is occasioned by the sequel and connexion of those laws which God has established for the regulation both of man and nature."

If, then, the eye of man (who is a depraved inhabitant of a world lying partly in ruins) is an organ so admirably fitted for extending our proepects of the visible creation-we may reasonably conclude, that organized beings, of superior intelligence and moral purity, possess the sense of vision in a much greater degree of perfection than man, in his present state of degradation— and that they may be enabled, by their natural organs, to penetrate into regions of the universe far beyond what man, by the aid of artificial helps, will ever be able to descry. It may not be altogether extravagant, nor even beyond the reality of existing facts, to suppose, that there are intelligences in the regions of Jupiter or Saturn, whose visual organs are in so perfect a state, that they can descry the mountains of our moon, and the continents, islands, and oceans which diversify our globe, and are able to de lineate a map of its surface, to mark the period of its diurnal rotation, and even to distinguish its cities, rivers, and volcanoes. It is quite evident, that it must be equally easy to Divine Wisdom and Omnipotence, to form organs with powers of vision far surpassing what I have now supposed, as to form an organ in which the mag nificent scene of heaven and earth is depicted, in a moment, within the compass of half an inch. There are animals whose range of vision is circumscribed within the limits of a few feet of inches; and, had we never perceived objec's through an organ in the same state of perfection as that with which we are furnished, we could have formed as little conception of the sublimity and extent of our present range of sight, as we can now do of those powers of vision, which would enable us to descry the inhabitants of distant worlds. The invention of the telescope shows, that the penetrating power of the eye may be indefinitely increased; and since the art of man can extend the limits of natu ral vision, it is easy to conceive, that, in the band of Omnipotence, a slight modification of the human eye might enable it, with the utmost dise tinctness, to penetrate into regions to which the imagination can set no bounds. And, therefore,

it is not unreasonable to believe, that, in the future world, this will be one property, among others, of the resurrection-body, that it will be furnished with organs of vision far superior to the present, in order to qualify its intelligent inhabitant for taking an ample survey of the "riches and glory" of the empire of God.

I have dwelt somewhat particularly on the functions of the eye, in order to show, that it is only when we take a minute inspection of the operations of the Creator, that his Infinite Wisdom and Intelligence are most distinctly perceived. 'The greater part of Christians will readily admit that the Wisdom of God is manifested in every object, but few of them take the trouble to inquire in what particular contrivances and adaptations this wisdom is displayed; and, therefore, rest satisfied with vague and general views, which seldom produce any deep impression on the mind. "The works of the Lord," which are "great" and admirable," must be sought out by all those who have pleasure therein;" and the more minutely they are inspected, the more exquisite and admirable do all his arrangements appear.

Were we to enter into an investigation of the visual organs of the lower animals, and to consider the numerous varieties which occur in their structure, position, and movements, and how nicely the peculiar organization of the eye is adapted to the general structure of the animal, and to its various necessities and modes of existence the operation of the same inscrutable Wisdom and Intelligence would meet our eye at every step. Birds, for example, which procure their food by their beak, have the power of seeing distinctly at a very small distance; and, as their rapid motion through the air renders it necessary that they should descry objects at a considerable distance, they have two peculiar mechanical contrivances,connected with their organs of vision, for producing both these effects. One of these contrivances consists in a flexible rim formed of bone, which surrounds the broadest part of the eye, and by occasionally pressing upon its orb, shortens its focal distance, and thus enables it to inspect very near objects. The other consists of a peculiar muscle, which draws back, as occasion requires, the crystalline humour, by which means it can take a distinct view of a distant landscape; and can pass from the sight of a very near, to the sight of a distant object, with rapidity and ease. In fishes, which live in a medium of a different refractive power from that of air, the crystalline humour has a greater degree of convexity, and more nearly approaches to a globular form than that of land animals-which conformation is essentially requisite to distinctness of vision in the watery element. A fish of course cannot see distinctly in air, nor a quadruped under water; and every person who has dived into the water with his eyes open, knows, that 7

though he may perceive the general forms and colours of objects, his vision is obscure and indistinct. In hares and rabbits the eyes are very Convex and prominent, so that they can see nearly quite round them; whereas, in dogs, which pursue these animals, the visual organs are placed more in the front of the head, to look rather before than behind them. Some animals, as cats and owls which pursue their prey in the dark, have the pupil of their eye so formed as to be capable of great expansion, so that a few rays of light may make a lively impression on their retina; while the eagle, which is able to look directly at the sun, has its pupil capable of being contracted almost to a point. Insects, such as the beetle, the fly, and the butterfly, whose eyes are incapable of motion, have several thousands of small transpa rent globes set in a convex hemisphere, every one of which is capable of forming an image of an object; so that they are enabled to view the objects around them without moving their heads. But, it would be beyond the limits of my plan to prosecute this subject any farther; enough has already been stated, to show, that the eyes of men and other animals are master-pieces of art, which far transcend the human understanding; and that they demonstrate the consummate wisdom of Him who planned and constructed the organical functions of the various tribes of animated existence,

I shall now conclude this branch of my subject, by presenting an instance or two of the mechanism of the bones, and the movements it is fitted to produce.

The bones of the human frame are articulated, or connected together, in different ways, but most frequently in the following manner. Either, 1. a bone with a round head is articulated with a cavity, and plays in it as a ball in a socket; or, 2. they are connected together by a hingelike articulation, which enables a bone to move up or down, backwards or forwards, like a door upon its hinges. An idea of these two motions, and the purposes they serve, may be obtained, by considering the construction of the pedestal of a telescope, and the joints on which it moves. One of the joints is of the nature of a hinge, by which a vertical motion, or a motion upwards and downwards is produced. A horizontal motion, or a motion towards the right hand or the left, is produced by a pivot moving in a socket; so that, by these two motions, the telescope can be made to point in any direction. Such is the nature of the articulations of the bones, and the movements they produce; and wherever one or other of these motions, or both of them combined, are requisite for the comfort and convenience of the individual, such a power of motion is uniformly found to exist. If the movement of a joint in every direction would, in any particular case, be found inconvenient, the hinge-like articulation is fixed upon ; but if a motion in every direction is

required for the convenient use of particular members, and for the variety of evolutions which a sentient being may have occasion to make, the ball and socket articulation is combined with the former.

For example, let any person, for a moment, consider the joints of his fingers, and compare them with the joint at his wrist, where the hand is connected with the fore arm. If he hold the back of his hand upwards, he will find that he can move his fingers upwards, or downwards; but he cannot turn them to the right hand, or to the left, so as to make them describe a circular motion. He will also find that his wrist is capable of a similar movement, so that the hand may be bent in a vertical direction. But, in addition to this motion, it is also capable of being turned in a horizontal direction, or from one side to another. In the former case, we have an example of the hinge articulation; in the latter, it is combined with an articulation which produces nearly the same effect as a pivot moving in a socket. Now, had the joints of the fingers been capable of the same motions as the wrist, the hand would have lost its firmness, and been incapable of performing a variety of mechanical operations which require objects to be held with a steady grasp. On the other hand, if the joint of the wrist had been formed in the same manner as the joints of the fingers, and confined to a vertical motion, the hand would have been incapable of one out of a hundred varied movements, which it can now perform with the greatest ease. In this case, we could not have bored a hole with a gimblet, cut down corn with a sickle, digged the earth with a spade, sewed clothes with a needle, tossed up a ball, or turned up the palm of the hand, for any of the useful purposes for which that motion was ordained. In short, without the rotatory motion of the wrist, the greater part of the operations connected with gardening, agriculture, cookery, washing, spinning, weaving, painting, carving, engraving, building, and other mechanical arts, could not be performed; and such of them as could be effected, would be accomplished only with the greatest inconvenience and labour. Any person may convince himself of this, by holding his hand in a horizontal position, and preventing his wrist joint from turning round, and then by trying what operations he can easily perform without the rotatory motion; and he will soon perceive with what exquisite skill the numerous movements of our animal frames have been contrived by the great Author of our existence. In each hand there are 27 bones, all of which are essential to the different motions we wish to perform. Every finger is composed of three bones, connected together by articulations, muscles, and ligaments. If, instead of three, each finger were composed of only one bone, it would be quite impossible for us to grasp a single object.

The same admirable contrivance may be per ceived in the movements of which the head is susceptible. It was requisite, in order to our convenience and comfort, that we should be --nabled to move our head backwards or forwards-to look up towards the heavens, or downwards to the ground. It was also expedient, that it should have a power of turning to the right, or to the left, so as to take in a considerable portion of a circle, wi hout being under the necessity of turning round the whole body. Accordingly we find, that both these motions are provided for, in the manner in which the head is connected with the vertebre. The head rests upon the uppermost of these bones, to which it is connected by a binge joint, similar to those in the fingers, which allows it to move backwards and forwards; and, by means of a round, longish process, or projection, which moves in a socket, it is enabled to move horizontally, as upon an axis. Had the first motion been wanting, we could not have looked up to the zenith, without laying flat on our back ; nor could we have looked to the ground, without placing our bodies in a prone position, and, in such a case, we could never have seen our own feet, unless when they were bent considerably forward. Had the second motion been wanting, we could have looked to nothing except the objects directly before us, without the trouble of turning round the whole body, either to the right, or to the left. But in the construction of our corporeal system, every thing is so arranged and adapted to another, as at once to contribute to ease, and facility of motion, in all the varied operations and movements we have occasion to perform; which circumstance forcibly demonstrates both the be nevolent intentions, and the admirable wisdom of Him" whose hands have made and fashioned us," and who "breathed into our nostrils the breath of life."

The above are only two or three out of a hundred of similar instances, which might be produced to show the benevolent care which has been exercised in arranging and articulating the system of bones, of which the prop-work of the human frame is composed. Were we to enter into an investigation of the actions and uses of the various muscles, the wonderful system of veins and arteries, the action of the heart, stomach, and bowels; the process of respiration, and insensible perspiration, and the system of nerves, glands, lymphatics, and lacteals-a thousand instances of Divine wisdom and beneficence would crowd upon our view, which could not fail to excite the pious and contemplative mind to join in the devotions of the "sweet singer of Israel," "I will praise thee; for I am fearfully and wonderfully made; marvellous are thy works, and that my soul knoweth right well."-But as I intended to present only a few specimens of the Wisdom of God, as displayed in the construction of

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