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panded, and by expelling some of the mercury from ON EMPLOYMENTS WHICH INJURE THE the tube at g' into the cup at g, it closes the aperture
EYE-SIGHT. of the pipe e; thus cutting off the supply of air to
· No. II. the fire. In a few minutes (the fire in the mean time
FUNCTIONS OF THE EYE-ABUSE OF THE ORGANS having abated its energy,) the air in the tube will
OF THE SENSES-CAUSES BY WHICH THE return to its former dimensions, and the mercury
EYE-SIGHT IS IMPAIRED. subsiding in the cup, air is again permitted to enter Having already described the chief parts and functhe ash-pit.
tions of the eye, and its appendages, we come now to The stove, of which we have thus attempted to consider how it is that this apparently elaborate apconvey a general idea, may be made of any required paratus performs its office. A pencil of light, that is, form or size. Instead of the self-regulating air valve
a bundle, or collection, of rays proceeding from any just described, it is fitted up with others of a very luminous object, falling upon the cornea, enters it
, simple construction, and which admit of being and is refracted or bent in its passage through the adjusted with the greatest accuracy by the hand.
aqueous humour, by which means the rays of the We have seen Thermometer-stoves of various forms, pencil are brought nearer to parallelism ; such of the some of them very beautifully designed, in operation. rays as
can pass through the pupil are further We have attentively watched the process going on
refracted by the crystalline lens, and the rays are within them, and have made ourselves acquainted
now no longer divergent, that is, they do not spread with their capabilities as heating agents. The result out from a point, but begin, in passing through this of our observations leads to this conclusion ; that if lens, to converge or proceed to a point, and this conthe Thermometer-stove be made in strict conformity vergency is perfected by means of the vitreous huwith the plain and simple rules which are so per mour, which brings the converging rays to a point spicuously laid down by Dr. Arnott, it will prove one exactly when they reach the retina. This process is of the most economical as well as most useful inven- undergone by every pencil of rays proceeding from tions of this rapidly improving age.
any object to which the eye is directed, and an exact Among the advantages of the Thermometer-stove, image of such object is depicted on the retina. If we may mention that it maintains an uniform tem. this convergent point do not quite fall upon the perature if required at night as well as by day, but retina, but before it, in the vitreous humour, the eye which can be increased or diminished in a few is said to be short-sighted ; if, on the contrary, these minutes. The fire within it may be kept alight with convergent points fall beyond the retina, the eye is out requiring attendance or any additional fuel for then long-sighted; but these and other defects to ten, or even a greater number of, successive hours. which the eye is subject, will be discussed at greater To warm a moderate-sized room, the cost of fuel will
length hereafter, not exceed a penny a day. No smoke, dust, vapour,
What we have above stated is the grand and imor other products of combustion, can possibly escape portant element in distinct vision ; the convergence into the room. The air is warmed, not heated, and
of the rays of a pencil to a point on the retina. An hence it is not deprived of its health-preserving pro- admirable adjustment of parts and of degrees of perties. There is no danger attending the use of the refractive power in the different humours of the eye Thermometer-stove ; it is more easily managed than produce this perfect convergency, and the mind can an open fire; and there is no waste either of fuel or
sufficiently appreciate and understand the mechanism of heat.
and purposes of all this exquisite arrangement,-but
here we have attained the utmost limit of our knowHe who can imagine the universe fortuitous or self-created, ledge,—we have traced upon the retina a picture of is not a subject for argument, provided he has the power the forms presented to the eye,—we see that this of thinking, or even the faculty of seeing. He who sees
retina is an expansion of a nerve called the optic no design, cannot claim the character of a philosopher: for philosophy traces means and ends. He who traces no
nerve, which proceeds from the retina into the brain, causes, must not assume to be a metaphysician; and if he the seat of the mind ;—but how the mind receives its does trace them, he must arrive at a First Cause. And impressions of light through the medium of this he who perceives no final causes, is equally deficient in optic nerve, is a question that has never been anmetaphysics and in natural philosophy; since, without this, swered, and probably never will be answered. The he cannot generalize,-can discover no plan, where there is student in science is constantly presented with certain no purpose. But if he who can see a Creation, without barriers beyond which he may not pass, --with cer80 he who can philosophize on it, and not feel the eternal tain limits to the inquiring powers of his mind, when presence of its Great Author, is little to be envied, even as subjects such as these are presented to him, which a mere philosopher; since he deprives the universe of all admit neither of demonstration or of analogical inits grandeur, and himself of the pleasures springing from ference, and are therefore beyond the purposes of those exalted views which soar beyond the details of tangible physical inquiry. Let him not, therefore, deal in forms and common events. And if, with that presence around him, he can be evil, he is an object of compassion, vague conjectures, which, however ingenious, must for he will be rejected by Him whom he opposes or rejects. still be unprofitable ; but rather let him turn to the -MACCULLOCH.
immense field which has already been cultivated so
successfully, and from whence rich harvests of COMPASSION.-Compassion is an emotion of which we knowledge have been gathered. We cannot join ought never to be ashamed. Graceful, particularly in youth, in the utterance of the querulous opinion, which, is the tear of sympathy, and the heart that melts at the tale because there is much that is unknown, denies the of woe; we should not permit ease and indulgence to contract our affections, and wrap us up in a selfish enjoyment. But existence of any knowledge at all; nor could we we should accustom ourselves to think of the distresses of
ever assent to the conclusion of the philosopher, human life, of the solitary cottage, the dying parent, and who said that his long life of study had taught him the weeping orphan. Nor ought we ever to sport with pain that he knew nothing; on the contrary, we and distress, in any of our amusements, or treat even the
assure the reader, that the arena of modern science meanest insect with wanton cruelty.—DR. BLAIR.
is so extensive, that a very long life and untiring Honour.—He is worthy of honour, who willeth the good of industry, would be inadequate to a fair investigation every man; and he is much unworthy thereof, who seeketh of its contents. his own profit, and oppresseth others.-CICERO.
The reader will now have some idea of the men'
chanical structure of the eye, and how, as far as we winking, as also by moving it about towards different know, this structure assists the powers of vision. We objects : if the eye be kept open and rigidly fixed coine, therefore, to the more direct purpose of our upon one object, its visual power rapidly declines. subject, namely, the consideration of those employ There is so much sympathy between various phy. ments of the eye by which its powers are impaired siological structures, that it often happens that a or destroyed. And here we must remind the reader morbid or diseased action of one structure will seri. of another law of nature as remarkable and beau, ously interfere with the functions of other structures tiful as any one in her code, if we may be allowed which are healthy. In the healthy eye, the retina, such an expression, where all appear alike beautiful the crystalline lens, the ciliary nerves, and the pupil, and remarkable when we are quite sure that we read must harmonize in their action: the many diseased and interpret them correctly ; it is this—that the affections of the organ which include weakness or perfect action of all the faculties, whether mental or indistinctness of vision, result from a weak state of physical, can be assured and perpetuated only by the retina, from the disordered action of the iris allowing them certain periodical intervals of perfect and ciliary apparatus ; this is brought about mainly repose. Now this may appear to be a truism, so by inflammation of the eye or its appendages, resultperfectly well known, that the necessity for its enun- ing from injudicious use of the organs. ciation in this place may be questioned by some : To discuss all the diseases of the eye resulting but we must remind our readers, that a principle is from abuses of its function, is manifestly a subject as important in its nature as it is unbounded in its for a large medical volume, the study of which application ; that it is the business of science not belongs to the medical pupil alone :-our purpose is only to discover principles, but to trace them to more confined : we intend to point out some of the effects where their presence is, perhaps, in no way cases of every-day occurrence, wherein the organ is suspected; that we often recognise the action of a injured by an habitual irritable treatment. We do principle in a few effects to which we are most obvi- not intend to employ technical terms, except a few, ously exposed, but we are often slow to recognise the which may be necessary to the comprehension of our same principle in effects which afford us a larger subject, and still less do we pretend to direct remeamount of pleasure or profit on the one hand than of dies, except by pointing out causes of injury to the pain on the other, which minister to our cupidity, our eye. In most cases our purpose will be effected, when, pride, our vanity; or which flatter one of those having clearly traced an ill effect to its cause, we say, * sins which do most easily beset us ;” and, indeed, remove or mitigate the canse, and the effect will prowe are frequently unable, from ignorance of the ex- bably cease. tent of a principle, to apply it as a cause to effects, In the pathology of the eye the term amaurosis is which we often think have no cause at all, or at least employed, in which is comprehended all those impera very remote one, which, if discovered, we pro- fections of vision resulting from a morbid action of nounce to be irremediable. But this sort of argu- the sentient apparatus belonging to this organ. The ment is unjust and unreasonable : in nature there term amaurosis is derived from a Greek word signiare only a few principles or first causes; some of fying to darken, and implies partial or total loss of these we are cognizant of—to all of them we are vision, according as the optic nerve, or retina, is parsubject : our business, therefore, is to study the code tially or totally paralyzed. This injury, or paralysis, of laws by which we are governed, to conform with is not generally manifested by external symptoms, the strictest obedience, since rebellion meets with and is therefore clearly distinguished from cataract, certain punishment, which, if ever it can be removed, opacity of the cornea, and closed pupil. This disease is removed only by a return to obedience.
is due to a variety of causes which it is not our The senses, then, require perfect repose in order business to discuss; such as disorganization of the to their perfect action, and this repose implies a retina, vascular turgescence, injury of certain nerves, removal of every cause which excites them to action. &c. Our purpose is, as we have already stated, to By the perfect action of an organ, we mean its legi- point out those common causes, of every-day occurtimate use and employment; the snuff-taker abuses rence, which the exercise of many arts and prohis organ of smell, and its functions are manifestly fessions is calculated to induce, and these causes may impaired. The manufacturer of perfumes is a bad be conveniently arranged into five heads, namely: judge of odour from the same cause. A nauseous 1st. Sedentary employments in which the head is smell ceases to be nauseous unless it is judged of at bent over work of various kinds; including those intervals. The sense of hearing is subject to loss of cases in which the eye is customarily employed on power from abuse of its functions : a man accus minute objects. tomed to the din of noisy factories, and who sits down 2nd. Where the eye is employed upon too strong undisturbed by and even unconscious of the presence or too little light : upon polished or reflecting surfaces. of that disturbance, which to a stranger is, at first, in 3rd. The habitual exposure of the organ to high sufferable, is scarcely conscious of delicate sonorous
temperatures. impulses. Blacksmiths hear soft tones with difficulty, 4th. The habitual exposure of the eye to acrid and examples have been abundant of old artillery- | fumes. men who have become quite deaf from the long 5th. The customary employment of optical glasses. practice of their profession. The sense of touch is less perfect in the ploughman than in the watchmaker, and most perfect, perhaps, in the blind man,
By the light of Divine revelation, Christianity enables us who by its means supplies in a great measure the accurately to discriminate between good and evil, right and loss of sight.
wrong: it teaches us to see things according to their own Taste also may be abused: the excited reveller
nature and in their proper colours: to behold those qualities
which are really vicious, deprived of the dazzling brightscarce distinguishes the flavour of his “ liqnid fire,” | ness, wherewith reason, impaired by passion, had invested as the banquet approaches its end, and the pampered them; and to contemplate those which are virtuous, disenepicure is gratified only by allowing to his palate in
cumbered from the clouds of worldly prejudice, and arrayed tervals of repose. The eye exhibits this principle in
in their native beauty. In a word, it teaches us to see a beautiful manner.
In its healthy state its function things, as they are in the sight of God, and not as they is being constantly intermitted in the process of appear according to the erroneous conception of men.
ON THE PERPETUATION OF PLANTS. The essential protection which the calyx affords, The care which the Creator has bestowed on the by enveloping everything while yet in a tender state, perpetuation of plants offers a wide field of inquiry. must not be forgotten; apt as we are to look on it as The collateral as well as the direct means of propa a superfluous part, from attending only to the exgation are very numerous, and the results very ex- panded flower. It would be endless to point out the tensive and valuable.
numerous forms and modes under which it guards The circumstance which is, perhaps, most striking the unopened flower, and above all from the access in the mode of propagation by seeds, is the apparent of water. The calyx of the rose, so useless when anxiety for their production, in the means adopted. expanded, is a familiar instance of protection afforded This is less sensible to common observation, where by a structure which, compared to the purpose, is the magnitude, the duration, and the uses of the very inartificial; and yet in this, and all similar plant itself, are conspicuous; but it becomes striking forms, that protection is complete. In the cistus, in the smaller and more perishable ones, and is often possessing a flower of unusual tenderness and delivery remarkable in the lowest parts of the scale. cacy, a varnish is superadded, for the purpose of Thus in the oak, we pay little attention to the pro-warding off the rains. The monophyllous calyces duction of seeds; or if noting it, we still know that present a structure more apparently efficacious, yet there is before us a being, destined to a life of so the protection is not more complete. And if the many centuries, that we scarcely think of its death, scale calyces of the grasses offer a much simpler or of the necessity of a system of perpetuation. contrivance, the security which they afford is not the
It is in the biennial and the annual plants that this less perfect. The calyx of the poppy is lax, and not anxiety for the continuation of the races is most very firmly closed; but as a counterbalance to this, obvious to common observation. Millions of indi- the flower bud is bent down by a curvature of the viduals seem to be utterly worthless : and there are stem, and erects itself only when the protection of even species without end, for which we can discover this deciduous guard is no longer wanted. The obno use, though desirous to find at least an insect stinacy with which this bud refuses to flower till it attached to each. Amid the hundreds of lichens and can erect itself, belongs to a still more interesting mosses, a very few would, as far as we can see, have circumstance in the physiology of plants: but under fulfilled the purpose which they appear solely to the present view, the inverted position enables the serve, in producing soils on naked surfaces. Yet in back of the calyx to ward off that water which these we trace the same care and the same anxiety. might have penetrated the less perfect junction at the The annual seems to grow for no other purpose than summit. to produce seeds; and that being accomplished, it That provision may here be pointed out in the dies. For this it struggles against every difficulty: liliaceous flowers, which, as a sheath, forms the suband under every check, every accident, every mutila- stitute for the absent calyx, while the leaves also are tion, it still labours for this end, as if it were a con sometimes arranged to perform the needful function. scious agent. We cut off its flowers, or cut down Under many different modes, the tulip, the genus itself, obstruct, impede it, in every manner, but it Allium, the grasses, and far more, will afford examples still resists, proceeding with an obstinacy of deter- of protection, given either to supply the want of a mination to effect this great object; while if, tired of calyx, or to add to the security which that affords. opposing it, we cease, it recommences, and having at And thus the seeds of the mosses are so embosomed length gained its purpose, dies. We can often even in the plant, at first, as almost to elude the botanist; prolong the annual life for another year, or more, by while they escape the chance of injury; to be elevated the same opposition; as if it was determined not to for dispersation, only when all hazard of failure is part with existence till it had obeyed its orders and past. fulfilled its destiny.
It is under all this care and concealment, that the The first mark of care, if a remote one, is found essential parts, destined to produce the perfect seed, in the contrivances for protecting the future flower are growing within; free from all hazard, till the ex. through the Winter, wherever such protection is ne- panding flower opens to the light that the work may cessary. In the buds, the beautiful packing, the be completed. And then do we begin to perceive investing scales, the down or hairs in some cases, and the utility of many other preparations towards this the varnish in others, are familiar: and, by these great end, the purposes of which we might not have contrivances, aided by that vital power, the action of understood before, and which he who looks on this which in resisting cold has not been explained, the interesting part of creation with a common eye, never most complete protection is afforded. In the bul The vanity of philosophy may smile, if it bous-rooted plants, the bud is not less effectually pleases, at what it may choose to term fanaticism, protected beneath the ground, partly by the depth of but it is he who seeks for the hand of the Creator in earth, and partly by the singular chemical properties every one of His works, who has found the true clue of the coverings, aided by the same resisting vitality of investigation ; since the purpose is that clue, and,
In other cases, the flower bud is not produced that to study the design and the Designer, are one. till the frosts are passed; and our attention may now And if the care of a parent for its offspring, the anbe directed to the provisions within it for the forma. | ticipations, the preparations, the watchfulness of a tion and ripening of the seeds. In a certain sense, mother, are objects of our admiration, shall we not indeed, the flower is a superfluity, an example of at least investigate the contrivances, the thought, the gratuitous beauty, while it also contains provisions anxiety, of the Great Parent of all, for the safety for the feeding of insects; yet with these are always and the life of these, His beautiful, but His lowest combined some uses for the seed itself, as, in many children; not inquire of his care for their perpetuity, cases, they are so numerous and remarkable that that not one shall be lost? Could more have been they cannot be overlooked. The reader need only be done; and if He has not done it, by whom then was reminded of the various ways in which they protect it effected? Who is it that contrived, who is it that the essential parts of the fructification, the stamina, watches over the lilies of the field, that not one of them and the pistils, on which the future seed depends; should perish from his land? Who is it that guards and of the contrivances for bringing the pollen into to maturity, even the minutest moss, and ensures it contact with the latter.
a posterity, that it shall not fail from the multitude
of His children, who, even in the vegetable world, simplest construction, but possessing the disadvantage look to Him for their food, their life, and their enjoy- of reflecting an inverted image. ment? Was it He: and is it He who cares not for But the inversion can be corrected by taking a little man, provides not for him, governs him not, watches more pains. Let A be a him not? Be it so, if it can afford satisfaction to piece of looking-glass fixthink that so it is : but it will not be so to him who ed in a wooden or brass will open his eyes on the world around him, and who | frame, and connected has learned, in everything, to look to the Cause, the with a piece of clear glass, Parent, of the universe. Would that I could per- B, so that the angle C B A suade him who has hitherto walked through creation shall be an angle of one without eyes, without thought, without a heart, to hundred and thirty-five take into his hand the first flower that shall present degrees, the image of an
Fig. 2. itself, and examine it as the work of some Being at object placed at F will be reflected from the lookleast who intended, and wrought, and cared. If elo- ing-glass at A, and proceed to the clear glass at B: quence has long done its worst for this unfortunate from this it will be reflected upwards to the eye at cause, there must be one who can sit down with the G, and the glass being transparent, the image and next flower that meets him in his Summer walk, and the hand will be seen at the same time; in this case ask himself, Whence came this, why is it here, why the image is erect. But, in general, neither of these all this beauty, why all this care? I have seen it plans are resorted to, for in both cases, as there are rise from a minute seed, I trace a series of cares and two reflecting surfaces from the glass, there will necontrivances that seed shall spring from it again, Icessarily be two reflected images, one of them cer. trace these under a thousand forms, I marvel at their tainly much less vivid than the other, but still suffiingenuity and their wisdom, I am astonished at an ciently visible to distract the eye anxietv which has neglected nothing, I see that an The optical portion of the Camera Lucida which end was intended, and I find that end attained. is usually sold consists of a prism. What more does man ever do to attain his objects, Fig. 3 is a section of the prism emwhen does he labour with more care and more know ployed; the angle A is equal to 224 ledge, and when does he succeed with more certainty ? degrees, c to 135 degrees, D 22} deDoes woman show more anxiety, more contrivance, grees, and B is a right angle of 90 for her offspring, than the Parent of this little flower | degrees. The solid nature of the prism
Fig. 3. has displayed ? And who can that careful, that will not allow the hand to be seen through its thickaffectionate parent be? No one! Even so was it ness, and the instrument is used in a different manner no one that reared me from helplessness to maturity, to the last contrivance. A is the I knew no parent's thought, no mother's care : there prism, B a moveable piece of brass, is no God. Can such a conclusion ever have entered having a small eye-hole in it at B; the heart of man? We know not how to believe him the reflected ray from c is received who has declared it.
near to this corner of the prism,
o [Abridged from MacCULLOCH's Proofs and Illustrations
and reflected upwards to the eye;
the eye-hole is so adjusted that
hand and pencil can be seen. In using the instrument THE CAMERA LUCIDA.
a vast deal depends on the proper adjustment of this The Camera Lucida, an invention of Dr. Wollaston, eye-hole. like the Camera Obscura, is an instrument employed If the light is very powerful on the object, and in making copies of drawings, and in portraying much less so on the paper, the part of the prism distant objects; but it is of greater service than the exposed through the hole should be small, and the Camera Obscura, being much more portable, and, if opening through which the paper is seen large in properly used, reflecting the image of the object with proportion. On the other hand, if the light on the out the least distortion.
drawing is weak, a larger part of the prism must be If a piece of thin glass is held at an angle of forty- uncovered. In copying a print, great care must be ive degrees with the horizon, at a small distance taken that the print itself is perfectly flat and perfrom the table, and a sheet of white paper is placed pendicular to the horizon, and that the side of the immediately beneath it, the reflected image of an object prism at B A, fig. 3, which is opposite the print, before it will be visible, by looking downwards upon shall be parallel to it. If this is not attended to, the it; and as the glass is transparent, the hand and print will be thrown into perspective and the copy be pencil can also be seen, and an outline of the image distorted. can be made upon the paper. In this case the image If the object is to be copied of its natural size, its is inverted. Such an instrument as this can be distance from the prism in front must be equal to made off-hand very easily.
the distance from the eye to the paper ; if it is to be Let o be a piece of thin
reduced it must be placed at a greater distance; if to plate-glass, about an inch
be enlarged, it must be brought nearer. and a quarter long, and
The Camera Lucida has been fixed to the eye-hole three-quarters of an inch
of a telescope or a microscope, in such a manner as wide; A a piece of wood in
to allow the objects within the field of vision to be which the glass is fixed, and
copied on paper. c a piece of pasteboard with a small hole in it, forming an eye-piece to keep the
LONDON: eye directed to one point.
JOHN WILLIAM PARKER, WEST STRAND. Let this little instrument be fixed on the top of a
PUBLISHED IN WEEKLY NUMBERS, PRICE ONE PENNY, AND IN MONTHLY PARTS, small stand, and you have a Camera Lucida of the
Sola by all Booksellers and Newsyeaders in the Kingdom.
E IT IS NOT GOO
nothing too minute, nothing too numerous, for his notice; INTRODUCTION.
that He who could create and arrange the whole, can also " When I consider thy heavens, the work of thy fingers; watch over and preserve the minutest parts of that whole. the moon and the stars, which thou hast ordained ;-what Our notions of great and small are derived from our own is man, that thou art mindful of him ? and the son of man, imperfect experience, and strikingly show the limited scope that thou visitest him?"—Psalm viii., 3, 4.
of our minds. The distance of the sun from the earth is a When the inspired Psalmist gave utterance to these quantity so immense, as almost to perplex the mind which words, he was evidently under the intluence of those feelings reflects on it; and yet that distance is small, compared of awe, wonder, and admiration, which are sure to be ex- with the distance of the fixed stars :—again, the minutecited in every intelligent mind, by the splendid and sublime ness of the nerves and smaller blood-vessels of the human phenomena presented to us by the heavenly bodies. When body, is such as to require the microscope to aid us in an we consider the magnitude and the number of those bodies, examination of their structure, and yet there are other the immense distances which separate them one from entire animals, endowed with life and powers of motion, another, the almost inconceivable velocity with which they which are so minute that the eye cannot perceive them. move, and that those which we can see form, probably, but The words great and small, then, are for man's use; to the a very small part of the whole number;—when we revolve Almighty nothing is great, nothing is small; the revolving these things in our minds, we are naturally brought to planet, and the animalcule whose world is a drop of water, reflect on our own insignificance in the grand scheme of being equally objects of his ever-active care. This divinelycreation. If a man, after having applied to himself the sustaining power of Him, in whom "we live, and move, vain and self-satisfying appellation of lord of the creation," and have our being," is so obvious, that we may exclaim were to remember that the glorious sun, and the planets with the poet Thomsonwhich revolve around it, form but one particular division,
Were every falt'ring tongue of man, class, or system in the universe,—that the earth is hut an
Almighty Father ! silent in thy praise, humble member of that system, and that he, man himself,
Thy Works themselves would raise a general voice, is but a moving particle on the surface of this earth,-he
E'en in the depth of solitary woods may well be expected to give utterance to the sentiments
By human foot untrod ;-proclaim thy power, of David, and to wonder how the Great Deity can regard
And to the choir celestial Thee resound,
Th' eternal cause, support, and end, of all!
Nothing is more calculated to elevate the mind, and to