Artificial light

“ In no one thing has man shown greater fertility of invention than in lighting; to nothing does he cling more tenaciously than to his devices for furnishing light. Electricity to-day reigns supreme in the field of illumination, but every other kind of artificial light that has ever been known is still in use somewhere. ”

“ When it is considered that mankind works under artificial light with an intensity of only a few foot-candles, the marvels of the visual apparatus are apparent. But it should be noted that the eyes of the human race evolved under natural light. They have been used to great intensities when called upon for their greatest efforts. The human being is wonderfully adaptive, but it could scarcely be hoped that the eyes could readjust themselves in a few generations to the changed conditions of low-intensity artificial lighting. ”

“ Monochromatic light is utilized in photo-micrography for the best rendition of detail. Light-waves have been utilized as standards of length because they are invariable and fundamental. Numerous other interesting adaptations of artificial light are in daily use. ”

“ In considering artificial light, we will avoid all efforts to analyze the different forms of energy, magnetic energy, electric energy, heat energy, mechanical momentum, radiating energy, and deal with result rather than with cause and effect. It will be sufficient to state as the deduction of the scientist that certain waves or vibrations which affect the fibers of the optic nerve are transmitted by the brain into color. (¶ 3.) Self-luminous bodies are bodies which produce light. ”

“ Artificial light may be controlled so that light of a satisfactory quality is properly directed and diffused. Sufficient intensities of illumination may be obtained and the failure of artificial light is a remote possibility as compared with the daily failure of natural light. With increasing cost of ground space, factories are built of several stories and with less space given to light courts, with the result that the ratio of window area to that of the floor is reduced. ”

“ Industrial superintendents are just beginning to see the advantage of adequate artificial lighting, but the low standards of lighting which were inaugurated when artificial light was much more costly than it is to-day persist tenaciously. When high intensities of proper illumination are once tried, they invariably prove successful in the industries. Not only does the worker see all his operations better, but there appears to be an enlivening effect upon individuals under the higher intensities of illumination. Mankind chooses a dimly lighted room in which to rest and to dream. ”

“ It is natural to inquire whether or not any mode of light-production now in use has a limiting luminous efficiency approaching the ultimate limit which is imposed by the visibility of radiation. The eye is able to convert radiant energy of different wave-lengths into certain fixed proportions of light. For example, radiant energy of such a wave-length as to excite the sensation of yellow-green is the most efficient and one watt of this energy is capable of being converted by the visual apparatus into about 625 lumens of light. ”

“ The development of the science of light-production has been so rapid during the past generation that adequate, efficient, and cheap artificial light finds mankind unconsciously viewing lighting with the same attitude as he displays toward his food and fuel bills. Another consequence of this rapid development is that mankind does not know how to extract the joy from modern artificial light. ”

“ So much energy is wasted in the production of heat-waves and ultra-violet waves which we do not want, that 90 per cent. or more of the power used in illumination is wasted. Would that the glow-worm, or even the dead herring, would yield us its secret! Phosphorus is the one thing we know as yet that suits the purpose, and—it smells! Indeed, our artificial light is not only extravagant in cost, but often poor in colour. The unwary person often buys a garment by artificial light, and is disgusted next morning to find in it a colour which is not wanted. ”

“ Artificial light in general is more satisfactory than natural light for many kinds of photographic work because through the ease of controlling it a greater variety of more artistic effects may be obtained. In ordinary photographic printing tungsten lamps are widely used, but in blue-printing the white flame-arc and the mercury-vapor lamp are generally employed. Not many years ago the blue-printer waited for the sun to appear in order to make his prints, but to-day large machines operate continuously under the light of powerful artificial sources. ”

“ First, it appears unwise to use the artificial light during the day; second, it appears possible that a few hours of artificial light in the evening would suffice for considerable forcing; third, it is possible that a much lower intensity of artificial light might be more effective per lumen than the great intensity used; fourth, it is quite possible that some other efficient light-source may be more effective in forcing the growth of plants. ”

“ If you want a really brilliant, clear, white light, you must trim the lamp yourself. A small piece of pale blue or neutral-tint glass interposed between the lamp and the microscope has a wonderful effect in diminishing the yellow hue which belongs more or less to all artificial lights which are produced by the combustion of oil or fat. We have no doubt but that in a few years we shall be rid of the clumsy and dirty machines that we call lamps, and have substituted for them the pure brilliancy of the electric light. ”

“ There cannot be any basic objection to artificial lighting, because most factories, for example, may be better illuminated by artificial than by natural light.
Of course, the lag of comfortable temperature behind daylight is responsible to some extent for a natural shifting of the ordinary working-day somewhat behind the sun. The chill of dawn tends to keep mankind in bed and the cheer of artificial light and the period of recreation in the evening tends to keep the civilized races out of bed. ”

“ Until the latter part of the nineteenth century artificial light was considered an expensive utility, but as modern lamps appeared which supplied adequate light at reasonable cost attention began to be centered upon utilization, and the lighting engineer was born. Gradually it is being realized that artificial light is no longer a luxury, that it may be used in great quantity, and that it may be directed, diffused, and altered in color as desired. ”

“ At the present time thousands of lighthouses, light-ships, and light-buoys guide the navigator along the waterways and into harbors and warn him of dangerous shoals. Many wonderful feats of engineering are involved in their construction and in no field of artificial lighting has more ingenuity been displayed in devising powerful beams of light. ”

“ The heliograph, which utilizes the sun as a light-source, has been widely used as a light-signaling apparatus and Drummond perhaps was the first to utilize artificial light with it. The disadvantage of the heliograph is the undependability of the sun. With the adoption of artificial light, various optical devices have come into use. ”

“ The highly developed artificial lighting of the present time may account for much of the vast industry of publication. Books, magazines, and newspapers owe much to convenient and inexpensive artificial light, for without it fewer hours would be available for recreation and advancement through reading. Schools, libraries, and art museums may be attended at night for the betterment of the human race. ”

“ The decorator deals with secondary light—that is, light reflected by more or less diffusely reflecting objects. The lighting expert has at his command not only this secondary light but the primary light of the sources. Lighting effects everywhere attract attention and even the modern merchant testifies that adequate lighting in his store is of advertising value. In all the field of spectacular lighting the superiority of artificial light over natural light is demonstrated.
Light is a universal medium with which to attract attention and to enthrall mankind. ”

“ Numerous investigators have studied the optical or radiant efficiency of artificial lights, i.e., the proportion of the total heat plus light energy emitted by the flame which is produced in the form of visible light. ”

“ Having become convinced of this power of light, the lighting expert may turn to artificial light, which is so easily controlled in direction, distribution, and color, and draw upon its potentiality. Not only is it easy to provide a lighting suitable to the mood or to the function of an interior but it is possible to obtain some variety in effect so that the lighting may always suit the occasion. A study of nature's lighting reveals one great principle, namely, variety. Mankind demands variety in most of his activities. Work is varied and alternated with recreation. ”

“ LIGHTING. Artificial light is generally produced by raising some body to a high temperature. If the temperature of a solid body be greater than that of surrounding bodies it parts with some of its energy in the form of radiation. Whilst the temperature is low these radiations are not of a kind to which the eye is sensitive; they are exclusively radiations less refrangible and of greater wave-length than red light, and may be called infra-red. As the temperature is increased the infra-red radiations increase, but presently there are added radiations which the eye perceives as red light. ”

“ How is it that the oxygen and hydrogen flame gives so little light, and with a solid body present, pours forth such a flood of brilliancy?
The production of artificial light by electrical and chemical agencies will necessarily find some consideration under their respective heads. There are numerous phenomena which connect themselves with luminous power, or appear to do so, which, in the present state of our knowledge, cannot come immediately under our attention. ”

“ Expressed in another manner, it is possible that a little light is much more effective than no light at all. Experiments with artificial light indicate very generally an increased growth.
Recently Hayden and Steinmetz experimented with a plot of ground 5 feet by 9 feet, over which were hung five 500-watt gas-filled tungsten lamps 3 feet above the ground and 17 inches apart. The lamps were equipped with reflectors and the resulting illumination was 700 foot-candles. This is an extremely high intensity of artificial illumination and is comparable with daylight in greenhouses. ”

“ The aim has been to show that artificial light has become intricately interwoven with human activities and that it has been a powerful influence upon the progress of civilization. The subject is too extensive to be treated in detail in a single volume, but an effort has been made to present a discussion fairly complete in scope. It is hoped that the reader will gain a greater appreciation of artificial light as an economic factor, as an artistic medium, and as a mighty influence upon the safety, efficiency, health, happiness, and general progress of mankind. ”

“ Artificial light in the home symbolizes independence of nature and protection from the elements and there is a firm desire to counteract the increasing whiteness of modern illuminants by means of shades of a warm tint. The white light is excellent for the kitchen, laundry, and bath-room, and for reading-lamps, but the warm yellow light is best suited for making cozy and cheerful the environment of the interiors in which mankind relaxes. An illuminant of this character can be obtained efficiently by using a properly tinted bulb on tungsten filament lamps. ”

“ However, the scientist is interested chiefly in the efficiency of the light-source which may be expressed in lumens per watt, or the amount of light obtained from a given rate of consumption or of emission of energy. This method of rating light-sources penalizes those radiating considerable energy which does not produce the sensation of light or which at best is of wave-lengths that are inefficient in this respect. ”

“ The control of light by means of reflectors has been studied for centuries, but until the advent of the electric arc the light-sources were of such large areas that effective control was impossible. Optical devices generally are considered in connection with "point sources," but inasmuch as no light can be obtained from a point, a source of small dimensions and of high brightness is the most effective compromise. ”

“ In fact, its development since it began in earnest has gone forward with ever-increasing momentum. On viewing the wonders of modern artificial lighting on every hand it is not difficult to muster the courage necessary to venture into its future. ”

“ And from the height of this perception all that had previously tormented and preoccupied him suddenly became illumined by a cold white light without shadows, without perspective, without distinction of outline. All life appeared to him like magic-lantern pictures at which he had long been gazing by artificial light through a glass. Now he suddenly saw those badly daubed pictures in clear daylight and without a glass. ”

“ The sun is of primary importance to mankind, but it serves in so many ways that it is naturally a compromise. It cannot supply just the desired radiant energy for one purpose and at the same time serve for another purpose in the best manner. It is obscured on cloudy days and disappears nightly. These absences are beneficial to some processes, but man in the highly organized activity of present civilization desires radiant energy of various qualities available at any time. In this respect artificial light is superior to the sun and is being improved continually. ”

“ The best instances of the advantages gained by the superinduction of artificial light, appear to be the Pietro Martire and the S. Lorenzo of Tiziano: if selection can be made from the works of a master, where to count is to choose. In the first, the stern light of evening far advanced in the background, is commanded by the celestial emanation bursting from above, wrapping the summit in splendour, and diffusing itself in rays more or less devious over the scenery. ”