Music Welcome to SnoozeCast, the podcast designed to help you fall asleep. Find us at snoozecast.com and wherever you listen to podcasts. If you'd like to listen at freefree, or unlock our entire vast and snoozy catalog of sleep stories, go to snoozecast.com slash plus. This episode is brought to you by Bright and Dazzling Objects. Tonight, we'll read from Spectacle Secrets written by George Cox and published in 1844. The real secret of the spectacle may be how to remember the difference between the role of an optician and optometrist and an ophthalmologist. While all three deal with eyes, and all three start with the letters OP, their roles are, of course, quite different. Let's have a quick review. An optician, like the author of tonight's fine publication, is like a skilled tailor, but for your vision. They fit in adjust glasses and contact lenses based on prescriptions. Those prescriptions would be written by an optometrist, who you can think of as a primary care physician, but for your eyes specifically.

They diagnose and treat common eye conditions. If something more serious comes up, the optometrist will likely refer you to an ophthalmologist, much like how a primary care doctor refers patients to a specialist. Now it's time to set our sights on getting a good night's sleep. Let's get cozy. Close your eyes.

Relax your body into the softness of your bed.

Now, take a few deep breaths. Spectacles and side saddles, we are quaintly informed, became common in England in the reign of Richard II. The ancients, however, knew the power of burning glasses, and one cunning rogue discovered a new way to pay old debts by means of a round stone or glass used in lighting of fires, with which he melted the bond written as usual in those days on wax. burning burning glasses were spheres, either solid or full of water. A long interval occurred before spectacles were constructed, and 300 years elapsed between the invention of spectacles and telescopes. Our eyes should have our nicest and most tender care since it is by them we are familiarized with objects of the most exquisite interest in beauty, abounding on the earth we inhabit and in the starry firmament above us. my soul while nature's beauties feast my eyes to nature's god contemplative shell rise from Doddsley. The faculty of sight should be estimated and regarded by us with more than ordinary care when we reflect that it is the medium through which the most exalted and gratifying impressions are received. And our watchful regard to its helpful preservation and agreeable exercise is the more required from the consideration that while to its admirable organization and delicate sense of perception, we stand so much indebted, those very qualities render it extremely sensitive to injudicious treatment. It would be a wholesome, fair, and proper regulation to restrain all from practicing as opticians, but those practically conversant with the production and application of lenses for the purpose of aiding and exercise of sight. It is considered indispensable for the surgeon and medical practitioner to prepare for his profession by a course of study, reading, and practical operations, and to be subjected to an ordeal where his capabilities are examined and tested. Such an arrangement, though it may sometimes be abused, guarantees to us practitioners who understand their duties, and thus are the many ills which human flesh is heir to, alleviated and subdued. It is a question often mooted. How far it is the duty of a just and equal government to interfere in such cases for the protection of its subjects. If a book is published, our opinion is almost insensibly influenced by what the reviewers say of it. If a new association, a company, or enterprise of any kind is projected, we look to the list of directors, committee, and patrons. Our education and universal custom induces us to pay deference to those whom we suppose to be possessed of superior information, to be men of character and reputation, and entitled from their position in society, to be men of character and reputation and entitled from their position in society to be regarded with respect. These legitimate feelings have been so poisoned and tampered with by those who have designed entered into a conspiracy to hoodwink the people and share the plunder.

And again by the hardly less criminal apathy of others, who, without dividing the spoil, have suffered the trickery to pass unexposed. That professional and literary men cannot but perceive distrust and want of confidence in their decisions. Now becoming general among the reflecting and intelligent classes of society, who see that they have been trifled with, and treated as credulous doops, and that they really have no guarantee for the merits of a production, the purity of a proposal, or the honesty and propriety of any measure to which distinguished names and lofty patronage are appended. The exposé of the practices of the railway, mining, and other bubble schemes illustrates this truth. The great and benevolent men who existed before us and devoted their time and contemplations to the interesting science of optics have fully and clearly demonstrated the laws which regulate the action of light, the cause and effect of luminous phenomena, and the principles upon which vision depends. We have the conclusive and unvering results of their numberless experiments, performed under every modification of circumstances, to guide us in establishing principles and rules of action, which the studious and practical opticians of our times have tested, and ascertaining them to be free from error, now adopt and act upon them. The capious and consequential may complain of this admission, as tending to detract from the importance with which they might otherwise be regarded. Not the optician who deserves that name is not anxious to array himself in borrowed

plumage, nor to appropriate as his own that which rightfully belongs to others. Granted that we act upon settled and incontrovertible philosophical principles, is it not infinitely more gratifying to have the assurance of a correct result? Then to be forever experimentalizing without arriving at a satisfactory conclusion. The skillful surgeon and the talented engineer are guided in their operations by certain fixed and universal laws. Yet no one will dispute that to perform the duties of either of those professions requires much application, skill, and expertness. Precisely so with the optician of the present day, he has fixed universal and certain data for his operations, and it is upon his intimate knowledge of these, and the careful and judicious application of them that his success depends. The human eye is composed of a series of humors and membranes. The outer coating called the sclerotica is exceedingly strong and the muscles which move the eye are attached to it. The white of the eye is a portion of this coating. The cornea urches out or projects from the eyeball. It is transparent and of a circular form. The next coating to the sclerotica is called the chloroides. It has no muscular motion except at its extremities near the front of the eye. The iris is next apparent. It attaches itself to the sclerotica by a cellular substance called the ciliary circle. According to the color of the iris, the eye is termed black, blue, hazel, et cetera. It is composed of two sets of muscle fibers, the one tending like radii towards the center. The other forming a number of circles can centric with the same center. The aperture in the iris is called the pupil. It is always round, but varies in diameter as the radial or the circular fibers of the iris are contracted or expanded. According to the quantity and quality of light, it is required to admit. Acting like a watchful sentinel to regulate the amount of rays requisite to transmit a perfect and well-defined image of objects onwards to the brain, which, without its agency, would appear one undistinguishable mass of confusion. The chamber of the eye is darkened by a posterior surface of the coroid chamber, having a lining of dark colored mucus called the pigmentum nigrum. The last coating of the eye is the retina, a delicate and most important membrane in the construction of this noble instrument. It is an expansion of the optic nerve directly emanating the brain, and is spread like a net of exquisite delicacy all over the surface of the coroides, terminating at the siliary ligament. It receives the images of objects by means of the rays of light that enter at the pupil. It is transparent, but it appears black on account of the dark pigmentum behind it. The optic nerve passes through a small aperture in the architectural dome containing the eye, and it conveys the impressions made on the retina into the depository of the brain, where the very form and spirit of the scene is now conceived. It is situated a little on one side of the center of the eye, inclining towards the nose. To describe more minutely the various fibers, humors, and ciliary processes of the eye, or to enter more fully into an anatomical arrangement, would be incompatible with the design of this publication, which is intended for the general reader, and therefore so simplified as that it is hoped he cannot fail to understand. The three transparent humors enclosed by the coats of the eye, the aqueous, the crystalline, and the vitrius are, however, too important to be passed over without some notice. The aqueous humor, it is which gives a protubrant figure to the cornea. It has a refractive power similar to that of water, which it also resembles in appearance. The crystalline humor is more transparent than the purest crystal. Its form is that of a double convex lens, which it also resembles in its use, as it converges the rays which pass through it from every visible object to its focus on the retina. It is suspended in a fine transparent sheathing. The shape or convexity of this natural lens alters occasionally and shifts a little backwards or forwards in the eye, so as to adapt its focal distance from the retina to the different distances of objects. The vitrious humor is situated at the back of the crystalline, filling nearly three-fourths of the globe of the eye.

It is surrounded by a thin capsule, which sends off a number of membranous processes into the vitreous substance, form cells which, communicating with each other, give a high degree of firmness and tenacity

to the whole. An object placed at the same distance from the eye as in a perfect eye has the focus carried beyond the retina. a convex lens applied to the eye compensates for any loss of capacity.

And... carried beyond the retina. A convex lens applied to the eye compensates for any loss of capacity, and converging the rays corrects the focal distance, and the image is now imprinted naturally on the retina. The reverse of this takes place in the case of the short-sighted, the humor is being more convex than in the perfect eye. The rays converge in a focus before they reach the retina. A concave lens carries the focus further on, and by its aid, an object will be depicted perfectly on the retina. What grandeur and sublimity of contrivance is here blended with simplicity of action and power of expression? How indispensable to a full appreciation of the bounties of nature and the beauties of art by which we are

surrounded. To be deficient of this heavenly gift is truly to have wisdom at one entrance quite shut out. Surely every consideration should influence us to treat this invaluable faculty with judicious care, instead of allowing it to be tortured and trifled with by the ignorant and unprincipled. Having surveyed the general construction and glanced at the inimitable mechanism of those windows of the soul, we shall be better prepared to understand the reasoning and to comprehend the principles upon which the science of optics is based. Those of my readers who have leisure to pursue this subject will find new light and more convincing illustrations attend their inquiry at every step.

It is a subject of bounding and beauty and interest, introducing us to new regions of sublimity and grandeur, where the contemplative mind will assuredly find ample scope and verge enough to gratify its most exalted anticipations. We have seen the admirable yet at the same time delicate contrivances by which the functions of the eyes are performed. It cannot fail to have occurred to us that a machine so beautiful and complete is liable to derangement and improper treatment by the wayward and the ignorant. If it is desirable that a person possessed of a well-constructed watch should understand its general action and know what treatment it should have to keep it in sound in under ranged order. Still more essential is it that every individual should possess a clear and familiar knowledge of the nature of vision, and understand the requirements of the eyes. I cannot forebear indulging a sanguine hope that the circulation of this little manual will open the eyes of its readers to the simple facts of the case and animate them to think and judge for themselves instead of giving a ready ear to the marvelous and ridiculous tails, which, though like the sailors' tough yarn, so often told that the cheat believes them himself, are nevertheless utterly devoid of truth. eyes, when in a sound and healthy state, instinctively adjust themselves at a distance of 12 inches from a book or paper when they are observing the same. This distance is found to be most natural and agreeable for when when we extend it to 16, 20, or 30 inches, the crystalline lens is stimulated to keep a distinct and clear perception until, as the distance increases, the object becomes less and less perceptible. When we are compelled to extend this natural distance, experience difficulty in reading small characters, or find it necessary to get more light on what we are observing. We may safely conclude that artificial assistance is needed, and that judiciously applied, the tendency to decay will be mildly arrested. The design of spectacles is to supply the loss of power, which is experienced by the eyes at different periods of life and arising from various causes. These productions of art are constructed with a close observance to and act upon the same principles as those by which the process of vision is regulated. Spectacles ought not to do more than maintain or preserve to us the capability of seeing at the natural distance. This is, in fact, all they are intended to affect. When the crystalline lens of the eye, losing its convexity, fails to converge the rays of light and bring bring them to their natural focus on the retina, and artificial lens of suitable convexity supplies to it this capability, and compensates for its gradual diminution of capacity. Thus lenses for assisting the sight are fashioned upon the optical

principles, so apparent in the mechanism of the eye itself, which it will be observed, is neither round nor flat, but of that nicely molded convexity, which is indispensable for the performance of its functions. If lenses were either spheres or planes, they likewise would be ineffective for the purpose proposed. There is not any material in existence beside pebble and glass, which is calculated for spectacle purposes. The pretended improvements, refractive transparencies, patent amber, crystal preservers, etc., are new fangled terms coined to entrap the uninitiated. Convex lenses are produced by a series of operations through which a glass or pebble passes, as shaping out from the rough piece, affixing them to the block or frame on which they are worked, grinding their surfaces to the form and focus required, in brass or iron tools of the curvature or radius corresponding. Thus to produce a glass or pebble of any given focal length, We use a tool which is a portion of a sphere or globe of 4, 5, 10 or any other given radius or half its diameter. For spectacles usually required, the focus of the pebble or glass thus fashioned varies from 60 inches down to 5 inches. The focus of a convex or magnifying glass is ascertained very readily thus. Hold the lens near to a white surface as a sheet of writing paper pinned to the side of the apartment opposite to the window. Shift the lens gently backwards and forwards until the object passes before it, as the window frames,

flower pots, or the Venetian blinds are seen inverted upon the paper.

Clearly and distinctly measure the distance from the paper to the lens.

And this distance is the focus or by placing a candle at the distance of 12 feet from the paper

and measuring as before, when the reflected image of the flame is shown most accurately on the paper, we again have the focus denoted. The one method is as much practiced as the other, though in ordering a lens of a given focus. I would recommend a person always to state the method by which he has determined the focus, whether by the sun or candlelight, which will prevent any mistake arising from the disparity between the two plans pursued. Concave lenses are made upon the same principle and pass through similar processes. They are designated by numbers. Thus, a concave lens, worked in a tool of four-inch inch radius is termed number 12, 5 inch, number 10, 10 inch, number 6, etc. to determine the radius or focus of a concave lens.

Apply to its surface a convex lens of the same focus, and holding the two together as one glass between the thumb and forefinger at some distance before the eye. Give the hand a gentle motion to and fro. And if the objects looked at through the lenses now in contact a pair fixed equal and of their natural size, then is the focus of the one corresponded to that of the other. But if the convex lens is not of the same focal length as the concave to which it is thus applied, then all objects looked upon will appear to shake and have a tremulous motion. Yn yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n y