Author: Aldous Huxley
Category: Literature
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The question now arises, what is adequate illumination?
The best illumination we have is full sunshine on a clear summer’s day. If you read in such sunshine, the intensity of the light falling upon the page of your book will be in the neighbourhood of ten thousand foot-candles — that is to say, the light of direct summer sunshine is equal to the light thrown by ten thousand wax candles placed at the distance of one foot from the book. Move from full sunlight to the shade of a tree or house. The light on your page will still have an intensity of about one thousand foot-candles. On overcast days, the light reflected from white clouds has an intensity of several thousand foot-candles; and the weather must be very gloomy for general outdoor intensities to fall as low as a thousand foot-candles.
Indoors, the light near an unobstructed window may have an intensity of anything from one hundred to five hundred foot-candles, depending upon the brightness of the day. Ten or fifteen feet away from the window the illumination may fall to as little as two foot-candles or even less, if the room is papered and furnished in dark colours.
The intensity of illumination diminishes as the square of the distance. A 60-watt lamp will provide about eighty foot-candles at one foot, about twenty at two feet, about nine at three feet, and, at ten feet, only four-fifths of one foot-candle. Owing to this rapid falling off in intensity with increase of distance, most parts of the average artificially lighted rooms are very poorly illuminated. It is common to find people reading and doing other forms of close work under an illumination of one or two foot-candles. In public buildings, such as schools and libraries, you will be lucky if you get as much as five foot-candles of illumination.
That it should be possible to do close work under illuminations so fantastically low compared with those which are met with out of doors in daytime is a remarkable tribute to the native endurance and flexibility of the sensing eyes and the perceiving mind. So great is this flexibility and endurance that a person whose eyes are unimpaired, and who uses them in the way that nature intended them to be used, can submit for long periods to bad lighting conditions and suffer no harm. But for a person whose eyes have undergone some organic impairment, or whose habitual functioning is so unnatural that he can only see with effort and under strain, these same conditions may be disastrous.
In his book, Seeing and Human Welfare, Dr. Luckiesh has described some very interesting experiments, which demonstrate the undesirable consequences of poor lighting. These experiments were designed to measure nervous muscular tension (an accurate indicator, as Dr. Luckiesh points out, of strain, fatigue, wasted effort and internal losses’) under varying conditions of illumination. The task assigned to the subjects of these experiments was reading; and the amount of nervous muscular strain was recorded by a device which measured the pressure exerted by two fingers of the left hand resting upon a large flat knob.
The subjects were kept unaware of the nature and purpose of the investigation — indeed, were deliberately thrown on a wrong scent. This eliminated the possibility of any conscious or voluntary interference with the results. A very large number of tests showed conclusively that, in all cases, ‘there was a large decrease in nervous muscular tension as the intensity increased from one to one hundred foot-candles. The latter was the highest intensity investigated, because this is far above prevailing levels of illumination in the artificial world. There was impressive evidence that this tension would continue to decrease if the level of illumination were increased to one thousand foot-candles.’ In other tests the subjects were exposed to improperly placed lights that threw a glare in their eyes. This glare was not excessive — just the average, moderate glare that millions of human beings habitually work and play by. Nevertheless it was quite sufficient to increase the tell-tale nervous muscular tension to a marked degree.
There is, so far as I know, only one kind of electric light bulb from which one can obtain a thousand foot-candles of illumination without excessive consumption of current. That is the 150-watt spotlight, described in the chapter on sunning. The parabolic and silvered back of this bulb acts as a reflector, and the light issues in a powerful beam, in which reading, sewing and other tasks requiring close attention and precise seeing can be performed in the best possible conditions.
During the daytime, people with defective sight should always make use of the best illumination available. Whenever possible, close work should be done near a window or out of doors. I myself have derived great benefit from reading for long periods at a stretch in full sunlight, either falling directly on the page, or, if the weather was too hot, reflected by means of an adjustable mirror, so that it was possible to sit in the shade, or indoors, and to enjoy the advantage of seven or eight thousand foot-candles upon the book. For some months, indeed, after giving up the wearing of spectacles, it was only in full sunlight, or under a spot lamp, that I could read comfortably for any length of time. But as vision improved, it became possible for me to make use of less intense illuminations. I still, however, prefer the spotlight to all others, and frequently work in full sunlight.
When reading in full sunlight, it is necessary to keep the eyes thoroughly relaxed by means of periodical brief sunnings and palmings. Many people will also find it easier to read if they make use of a slot cut in black paper, as described in an earlier chapter. When these precautions are taken, reading under ten thousand foot-candles can be very helpful to those whose vision is defective. Falling upon the centre of sight, the image of the intensely illuminated print stimulates a macula which has become sluggish and insensitive through habitual wrong use of the organs of seeing. At the same time, the clarity and distinctness of the sunlit letters exercise a most wholesome influence upon the mind, which loses its habitual strained anxiety about seeing and acquires instead an easy confidence in its ability to interpret the sensa brought to it by the eyes. Thanks to this confidence and to the stimulation of the sluggish macula, it becomes possible, after a time, to do one’s seeing no less effectively under lower intensities of illumination. Ten thousand foot-candle reading is a preparation and an education for hundred foot-candle reading.
Owing sometimes to organic defects of the eyes, sometimes to ingrained habits of improper functioning, sometimes to generalized ill-health, certain persons are peculiarly sensitive to intense light. For these it would be unwise to plunge directly into ten thousand foot-candle reading. Following the techniques described in the chapter on sunning, they should gradually accustom themselves to tolerate greater and greater intensities of illumination, not only directly on the closed and open eyes, but also on the printed page before them. In this way, they will come by slow degrees to be able to enjoy the advantages of good lighting — advantages from which their organic or functional photophobia had previously cut them off, forcing them to strain for vision in a perpetual twilight.
In conclusion, it seems worth while to say a few words about the fluorescent lighting, now so extensively used in factories, shops and offices, on account of its cheapness. There is good evidence that this kind of lighting adversely affects the vision of a minority of those who have to do close work under it. One reason for this must be sought in the composition of the light itself, which does not come from an incandescent source, as does natural sunlight or the light from a filament bulb. Nor is this all. Fluorescent lighting throws almost no shadows. Consequently the element of contrast, so immensely important to normal seeing, is conspicuously absent from rooms illuminated by fluorescent tubes. Shadows, moreover, help us in our estimation of distances, forms and textures. When shadows are absent, we are deprived of one of our most valuable guide-posts to reality, and the accurate interpretation of sensa becomes much harder. This is one of the reasons why the organs of vision tire so much more easily on a day of uniform high cloud than on one of bright sunshine. Fluorescent lighting produces an effect somewhat similar to that produced by the diffused glare reflected from high thin clouds. To eyes that have been evolved to adapt themselves to light proceeding from an incandescent so
urce, and to minds that have learnt to make use of shadows as guides to correct interpretation, perception and judgment, fluorescent lighting cannot but seem strange and baffling. The wonder is that it is only a minority of people who react unfavourably to such lighting.
If you happen to belong to the unlucky ten or fifteen per cent, of the population which cannot work under fluorescent light without suffering from bloodshot eyes, swollen eyelids and lowered vision, the best thing you can do, of course, is to find a job which permits you to work out of doors, or by the light of incandescent filament lamps. The next best thing is to palm frequently, and get out of the fluorescence as often as possible for a few minutes of sunning. At night, as a substitute for sunning, take the light of a strong incandescent filament lamp upon the closed and open eyes. The movies constitute another excellent therapeutic measure for those who suffer in this way. Looked at in the proper way, they can be wonderfully restful and refreshing to eyes which react badly to the peculiar composition of fluorescent light and to minds which are baffled by the shadowless world of low contrasts, in which that light compels them to work.
APPENDIX I
AFTER I had completed the manuscript of this book, a correspondent sent me a copy of the following article, which appeared as an unsigned editorial annotation in the British Medical Journal of September 13th, 1941.
PERFECT SIGHT WITHOUT GLASSES
A letter in this week’s Journal from Dr. J. Parness draws attention to a statement recently broadcast by Dr. Julian Huxley on the practice of correcting visual defects without the use of glasses. Before condemning such a practice it would be as well to examine the evidence in support of it. There are a variety of methods based on hypotheses of varying degrees of tenuity. The system expounded by W. H. Bates in his Cure of Imperfect Sight by Treatment Without Glasses (New York, 1920) has the advantage over competitive systems in that its principles are publicly stated. Bates holds that the refractive state is dynamic and is constantly changing. The changes in refraction are produced by the nerves and tissues of the extra-ocular muscles, the lens itself playing no part in accommodation. Defective vision is a psychic phenomenon, affection of the brain centres first disturbing the macula and then the whole retina. Treatment aims at inducing ‘cerebral relaxation,’ for when the mind is at rest vision is normal. In thirty years’ work on refraction Bates found few people who could maintain ‘perfect sight’ for more than a few minutes at a time, and he often saw ‘the refraction change half a dozen times or more in a second, the variation ranging all the way from twenty dioptres of myopia to normal.’ As no ophthalmologist has the necessary skill and speed to observe half a dozen or more changes in refraction in the space of a second (‘blitz retinoscopy,’ as it might be called), no one is in a position to contradict this basic tenet of Bates. And ophthalmologists still cling to the theory, based upon physiological evidence, that accommodation is brought about by the changing curvature of the lens. Bates illustrates the influence of the mind on refraction by the effect of strain. Since strain implies mental unrest, changes in refraction occur in all conditions inducing such unrest. Thus ‘a patient 25 years old had no error of refraction when he looked at a blank wall without trying to see (i.e. under complete relaxation and total absence of strain); but if he said he was 26, or someone else said he was 26, he became myopic (as shown by Bates’s rapid retinoscopy). The same thing happened when he said or tried to imagine that he was 24. When he stated or remembered the truth his vision was normal, but when he stated or imagined an error he had an error of refraction.’ There is also the case of the little girl who told a lie. The retinoscope revealed a change towards myopia the moment she replied ‘No’ to the question, ‘Did you have an ice-cream?’; while she was giving truthful answers ‘the retinoscope indicated no error of refraction.’ This appears to be, so to say, a physical expression of the inward eye of the conscience.
A queer assortment of evidence is brought forward to prove that the refractive changes in the eye are produced by the extraocular muscles. There is, for example, the ‘proof’ that aphakic patients are able to read small type with distance glasses. That the daily experience of ophthalmologists is to the contrary is perhaps of some significance, though obviously not as significant as the few instances Bates records, for which, incidentally, perfectly good explanations are available, as anyone acquainted with the literature knows. There is, indeed, an extensive and controversial literature on the actual mechanism whereby the contour of the lens changes during accommodation; the facts themselves are not disputed — except by Bates, who produces experimental evidence that in the fish removal of the lens does not interfere with accommodation. The fish experiment is amply illustrated by photographs, but there is no reference to the fact that accommodation in the fish is different physiologically and anatomically from that of the mammal. Mammalian experiments, mainly on the rabbit and cat, are recorded, and here the rather startling point emerges that a nerve or muscle cut across and tied up again will carry an impulse on being tied, though physiologists would not expect any such result before days or weeks had elapsed. Mammalian anatomy is also illuminated in these experiments. Apparently the standard teaching that the cat is endowed with a superior oblique muscle is not correct. It should be added that this is only an incidental observation; but that pharmacologists err in believing that atropine acts only on unstriped muscle is part of the general argument, for Bates found that this drug will paralyse the extrinsic muscles which produce accommodation. One experiment, illustrated in fig. 23, appears to show that the dead fish still has a living mind; its brain is pithed to induce relaxation.
The treatment based on these revolutionary observations aims at mental relaxation, and the pithed fish appears to be its prototype. The Bates system of treatment seems to have many devotees, and one incident may be worth noting. In 1931 the Republican Ministry of Public Health of Prussia warned against this method as a form of quackery, but in Hitlerite Germany a voluminous literature on the subject has spread the cult and there is apparently no lack of practitioners and patients.
It will be noticed that this article contains two main lines of argument.
First: Bates’s method of visual education cannot be sound, because it is used by Germans.
Second: Bates’s method of visual education cannot be sound, because certain experiments devised to confirm the hypothesis, by which Bates sought to explain the success of his method, were not conducted properly.
The first argument is exactly like that which was used, more than a century ago, to discredit the stethoscope. Readers of John Elliotson’s papers will recall his account of this ludicrous episode in the history of English medicine. Owing to anti-French prejudice, it was twenty years or more before Laennec’s invention came into general use among English physicians.
In precisely the same way, owing to prejudice against magnetizers and mesmerists, hypnotism was under the ban of official British medicine for an even longer period. For half a century after Braid had formulated his classical hypothesis and Esdaile had performed scores of major operations under hypnotic anaesthesia, the British Medical Association officially held that there was nothing in hypnotism but fraud and quackery.
Medical history has a dismal way of repeating itself in these matters, and it looks as though visual education were to suffer the same fate as hypnotism and the stethoscope.
I may add that the argument from nationalism hardly seems justified in the present instance. The art of seeing was worked out by an American physician and is extensively taught at the present time in the United States and England. ‘Seeing-schools’ have also existed for many years in Germany. Some of these schools were doubtless bad and deserved the censure of the Republican Health Ministry; but others, as it would appear from an article contributed in 1934 by an army surgeon to the Deutsche Medizitnische Wochenschrift, must have been excellent. In this article, Dr. Drenkhahn records that, in many cases of refractive error among army recruits, he found that marksmanship was better when t
he men wore no corrective glasses, but underwent a course of visual training at a seeing-school. To those who notice any falling-off of vision, Dr. Drenkhahn gives the following advice: not to go immediately to an eye specialist, who will generally prescribe glasses, but to consult the family physician and, when he has taken steps to correct the general physical and psychological condition, to go to a seeing-school and learn the proper way to use the eyes and mind.
So much for the first line of argument. The second is equally irrelevant, being based, not on prejudice this time, but on mental confusion and bad logic. For, incredible as it may seem, the writer of the article entirely fails to distinguish between two totally different things: the primary evidence confirming the existence of certain phenomena, and the secondary evidence adduced to substantiate the hypothesis, in terms of which those phenomena are explained. The phenomena, which Bates sought to explain in terms of his unorthodox theory of accommodation, were those marked improvements in vision which regularly followed the practice of certain educational techniques. The evidence for the occurrence of such phenomena can be supplied by the thousands of persons who, like myself, have derived benefit from following the procedures in question, and by the scores of conscientious and experienced instructors who teach the method. If the writer really wanted to know about this evidence, he would get in touch with a few reliable teachers, ask permission to watch them at work and, if his own vision is defective, take a course of visual re-education. Instead of that, he seeks to discredit the whole idea of visual re-education by denying the validity of the experiments used by Bates to support his explanatory hypothesis.
Needless to say, the idea of visual education emerges unscathed from this hopelessly misdirected attack. For it is obvious that, even if this secondary evidence were untrustworthy, even if the hypothesis supported by that evidence could be proved to be incorrect, this would make absolutely no difference to the facts which that hypothesis was originally intended to explain. In the history of human effort, effective arts have always preceded correct explanatory hypotheses. Thus, an art of metallurgy existed for several thousands of years before the formulation, in the present century, of satisfactory hypotheses to account for the phenomena of tempering and alloying. According to the view expressed in the article, the incorrectness of their hypotheses should have made it impossible for the old smiths and founders to possess an art of metal working. Again, if the writer’s argument made sense, there could be no such thing as modern medicine. Our knowledge of the human mind-body is limited and patchy, and our theories about it are admittedly inadequate. Nevertheless, an effective art of medicine exists, in spite of the fact that many medical hypotheses will, in the future, certainly be proved false, while new hypotheses will be formulated, of which contemporary physicians cannot even dream. Bates’s theory of accommodation may be as incorrect as were the eighteenth-and nineteenth-century explanations of the efficacy of lime-juice in cases of scurvy. Nevertheless scurvy was cured by lime-juice, and Bates’s method of visual education actually works.