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lo see distinctly objects at the same distance a', which shey were abla to perceive them before they became short-sighted.
“When the eye (says Dr. Young) is possessed of too great refracrive power for the distinct perception of distant objects, the pupil is generally large, so that the confusion of the image is somewhat lesBened by partially closing the eyelids; and from this habit an eye so formed is called myopic. In such cases, by the help of a concave lens, the divergence of the rays of light may be increased, and a vir. tual image may be formed, at a distance, so much smaller than that of the object as to afford perfect vision. For a long-sighted or presby.. opic eye, on the contrary, a convex lens is required, in order to obtain a virtua. image at a greater distance than the object; and it ofter. happens that the rays must be made not only to diverge less than before, but even to converge toward a focus behind such an eye, in order to make its vision distinct. Presbyopic persuns have, in general, a small pupil, and therefore seldom acquire the habit of covering any part of it with their eyelids."
If the humors of the eye, through age or weakness, have shrunk or decayed, the cornea will then be too Aat, and the rays not being sufficiently bent or retracted, arrive at the retina before they are united in a focus, and would meet, if not intercepted, in some place behind it. They, therefore, (unless influenced by artificial means,) do not make an impression sufficiently correct and forcible, but form an indistinct picture on the bottom of the eye, and exhibit the object in a confused and imperfect manner. This defect of the eye is therefore remedied by a double-convex jens, such as the common spectacle-glasses, which, by causing the rays to converge sooner than they otherwise would, afford that aid to this defect of nature wbich the circumstances of the case may require, the convexity of the glass being always proportioned to the deficiency in vision.
If, on the contrary, the cornea is too convex, the rays will unite in a focus before their arrival at the retina, and the image will aiso be indistinct. This defect is remedied by concave glasses, which cause the rays to diverge; and consequently, by being properly adapted to the case, will enable the eye to form the image in its proper place.
By the aid of convex glasses of thirty-six or thirty inches focus, persons, whose sight is beginning to be unequal to read small print, or to work without fatiguing or paining their eyes, will be enabled to do either; and, if properly chosen, by the ease and comfort they afford will tend materially to preserve the sight: hence their name of predorvers, which, however, is a term as applicable to all the various gra. lations of glasses. The length of time that will elapse before it may De necessary to change these first spectacles, must depend upon the same circumstances which I have mentioned as creating the necessity for using them at all. However, it may be said that they will com: monly serve for reading in the daytime about six or seven years.
As soon as the eye begins to be little better with the glasses used than without them, it is time to change them for more powerful mag. nifiers. And the second signt, vr thirtv inches' fociis, are necessary; thoug.. these should not be cox hastiiy adopted by those who wish to
preserve their sight unimpaired to old age ; but they should be conient to use them as sparingly as possible--only when vnavoidable. Many have worn out their sight prematurely by using spectacles of too great a magnifying power, or of improper materials and faulty workmanship, to which their eyes have soon become accustomed; but they speedily exhaust the resources of art, and, before death, have bee come totally blind.
Those who are about to commence wearing glasses, as they cannot know what will suit their eyes, will do well to borrow a set of glasses, consisting of spectacles of regular gradations of power, and try al home, for a few days, which suit them best. they should make the ex. periment by day-light and candle-light, in that posture of the body in which they will be most used.
Almost all persons, on first wearing spectacles, if they keep them on a few hours, complain of fatigue and uneasy sensations in their eyes ; and this, even though they have been judiciously chosen, and when they were needful. Such weariness will be most felt by candle-light, and is caused, no doubt, by the eyes, for some time before resorting to glasses, having been tasked beyond their ability; and not, as is com monly supposed, by the artificial light, though that, probably, contributes to it.
Those whose avocations or amusements render the assistance o magnifiers necessary, ought to bear in mind, that the lower the degree of magnifying power possessed by their glasses, the less the eye will be fatigued by them, the less constrained the position of the body in using them, and the larger, as well as more uniformly distinct, the field of view embraced by them. Where only a moderate magnifying power is required, I would recommend, instead of a single magnifier the use of spectacles of nine inches' focus, which will enable the eye to be directed to minute objects without weariness for a longer time than if an eye-glass only be used, as well as being of material benefit in preserving one of the eyes from becoming injured, by being constantly unemployed.
The use of spectacles is every way preferable for short-sighted persons to single eye-glasses ; a strong confirmation of the truth of which may be found in the fact that Mr. George Adams, a late highly celebrated English optician, asserted that he did not recollect an instance of a short-sighted person who had occasion to increase the depth of his glasses, if he began with spectacles; but, on the other hand, he knew many cases where only one eye had been used, in which the individuals' had been obliged repeatedly to change their glasses for concaves of higher power. Indeed, the advantage of a pair of spectacles over an eye-glass is very evident, from the circumstance that all objects are much brighter when seen with both eyes than whon looked at with only one.
THE YOUNG MAN'S MANUAL.
uable information, but the three prescriptions wisich follow are worth infinitely more than all the rest. I strongly coinmend them to the ate lention of every young man into whose hands this book may fall.
(1.) Upon getting a Wife. Young man! if you have arrived at the right point in life for it, let every other consideration give way to that of getting married. Don't think of doing anything else. Keep poking about among the rubbish of the world till you have stirred up a gem worth having in the shape of a wife. Never think of delaying the matter; for you know that delays are dangerous. A good wife is the most constant and faithful conipanion you can possibly have by your side, while performing the journey of life-a dog isn't a touch to her. She is of more service, too, than you may at first imagine. She can “smooth your lineu and your cares" for you--mend your trousers, and perchance your manners—sweeten your sour moments as well as your tea and coffee for you-ruffle, perhaps, your shirt bosom, but not your temper; and, instead of sowing the seeds of sorrow in your path, she will sew buttons on your shirts, and plant happiness instead of harrow teeth in your boson. Yes—and if you are too confoundedly lazy or too proud to do such work yourself, she will chop wood, and dig potatoes for dinner: for her love for her husband is such that she will do anything to please him-except receive company in her everyday clothes.
When a woman loves, she loves with a double-distilled devotedness ; and when she hates, she hates on the high pressure principle. Her love is as deep as the ocean, strong as a hempen halter, and as immutable as the rock of ages. She won't change it, except it is in a very strong fit of jealousy, and even then it lingers, as if loth to part, like evening twilights at the windows of the west. Get married, by all means. All the excuses you can fish up against “ doing the deed” ain't worth a spoonful of pigeon's milk. Mark this--if, blest with health and employment, you are not able to support a wife, depend upon il you are not capable of supporting yourselt. Therefore, so much more the need of annexation; for, in union, as well as an onion, there is strength. Get married, I repeai, young man! Concentrate your affections upon one object, and not distribute them cruinb by crumb, among a host of Susans, Sarahs, Marys, Loranas, Olives, Elizas, Augustas, Betsies, Peggies, and Dorothies--allowing each scarcely enough to nibble at. Get married, and have somebody to cheer you as you journey through this “lowly vale of tears”-somebody to scour up your whole life, and whatever linen you possess, in some sort of Sunday-go-to-meeting order.
Young woman, I need not tell you to look out for your husband, for I know that you are fixing contrivances to catch one, and are as naturally on the watch as a cat is for a mouse. But one word in your ear, if you please. Don't bait your hook with an artificial fly of beauty ; if you do, the chances are ten to one that you will catch a gudgeon-some silly fool of a fish that isn't worth his weight in sawdust. Array the inner lady with the beautiful garments of virtue, modesty, truh, morality, and unsophisticated love; and you will dis.
pose of yourself quicker, and so much better advantage thau you would if you displayed all the gew-gaws, flippejigs, fol-derols, and fiddle-de-dees in the universe. Remauber that it is an awfu. thing to live and die a self-manufactured old maid.
My hearers-get married while you are young; and then when the frosts of age shall fall and wither the flowers of affection, the leaves of connubial love will still be green, and, perchance, a joyous offspring will surround and grace the parent tree, like ivy twining and adorning the time-scathed oak.
(2.) Upon choosing a Wife. Young man, a word in your ear, when you choose a wife. Don't ve fascinated with a dashing creature, fond of society, vain, artistical, and showy in dress. You do not want a doll or a coquette for a partner. Choose rather one of those retiring, modest, sensible girls, who have learnt to deny themselves, and possess some decided character. But above all, seek for a good disposition. No trait of character is more valuable in a female than the possession of a sweet temper Home can never be made happy without it. It is like the flowers that spring up in the pathway, reviving and cheering us. Let a man go home at night, wearied and worn by the toils of the day, how soothing is a word dictated by a good disposition! It is sunshine falling on his heart. He is happy, and the cares of life are forgotten.
(3.) How to treat a Wife. First get a wife-secondly be patient. You may have great trials and perplexities in your business with the world; but do not therefore carry to your home a clouded or contracted brow. Your wife may have had trials, which, though of less magnitude, may have been as hard to bear. A kind, consoling, and tender look, will do wonders in chasing from her brow all clouds of gloom. You encounter your difficulties in the open air, fanned by hozven's cool breezes, but your wife is often shut up from these healthful influences, and her health fails, and her spirits lose their elasticity. But oh! bear with her; she has trials and sorrows to which you are a stranger, but which your tenderness can deprive of all their anguish. Notice kindly her little attentions and efforts to promote your comfort. Do not take them all as a matter of course, and pass them by; at the same time being very sure to notice any omission of what you may consider her duty to you. Do not treat her with indifference, if you would not sear and palsy her heart, which, watered by kindness, would, to the latest day of your existence, throb with sincere and constant affection
Sometimes yield your wishes to hers. She has preferences as strong as you, and perhaps just as trying to her to yield her choice as to you. Do you find it hard to yield sometimes ? Think you it is not hard for her to give up always ? If you never yield to her wishes, there is danger that she will think you are selfish, and care only for yourself, and with such feelings she cannot love you as she ought. Again, show yourself manly, so that your wife can look up to you, and feel that you will ac: nobly, and that she road confide in your judgment
HINTS ON ETIQUETTE. (1.) In all your associations, keep, constantly in view the adage, too much freedom breeds contempt.
(2.) Never be guilty of practical jokes : if you accustom yourself to thein, it is probable you will become so habituated as to commit them upon persons who will not allow of such liberties : I have known a duel to arise from a slap on the back.
(3.) If there be another chair in the room, do not offer a lady that from which you have just risen.
(4.) Always suspect the advances of any person who may wish for your acquaintance, and who has had no introduction: circumstances may qualify this remark, but as a general principle, acquaintances made in a public room or place of amusement are not desirable.
(5.) Never converse while a person is singing ; it is an insult not only to the singer, but to the company.
(6.) The essential part of good breeding is the practical desire to afford pleasure, and to avoid giving pain. Any man possessing this desire, requires only opportunity and observation to make him a gentleman.
(7.) Always take off your hat when handing a lady to her carriage, or the box of a theatre, or a public room.
(8.) If, in a public promenade, you pass and re-pass persons of your acquaintance, it is only necessary to salute them on the first occasion.
(9.) Do not affect singularity of dress by wearing anything that is so conspicuous as to demand attention; and particularly avoid what I believe I must call the ruffian style.
(10.) Never lose your temper at cards, and particularly avoid the exhibition of anxiety or vexation at want of success. if playing whist, not only keep your temper, but hold your tongue; any intimation to your partner is decidedly ungentlemanly.
(11.) Let presents to a lady be characterized by taste-not remarkable for intrinsic value.
(12.) Except under very decided circumstances, it is both ungentlenianly and dangerous to cut a person : if you wish to rid yourseif of any one's society, a cold bow in the street, and particular ceremony in the circles of your mutual acquaintance, is the best mode of conduct to adopt.
(13.) Never introduce your own affairs for the amusement of a company; it shows a sad want of mental cultivation, or excessive weakness of intellect: recollect, also, that such a discussion cannot be interesting to others, and that the probability is that the mos patient listener is a complete gossip, laying the foundation for some tale to make you appear ridiculous.