Reading Room in the Congressional Library at Washington. No matter where the reader sits the glare from several naked Tungsten incandescent lights is bound to hit him full in the eye. A most impressive example of the way not to light a reading room or any other place of public assembly. every exposed light in the theater, and although the architectural arrangement made it impossible to attain ideal results, he managed to hang the lights so that none could be seen from any part of the auditorium. Instead of a direct glare the light was thrown against the ceiling from which it was reflected in a soft diffused glow at a carefully calculated intensity that caressed and soothed tired eyes like summer zephyr. Every one who came in gave a sigh of relief and just relaxed rather than sat down. The audiences thought they were witnessing the supreme efforts of transcendant genius on the stage when, as a matter modulated light that put them in such fine humor. It was the new illuminating engineer, not the ancient soubrette, who transformed a. hopeless failure into success in its most aggravated form. This is a fair example of what the illuminating engineers are doing whenever they get a chance. It may be added that the chances are coming along about as fast as they can be taken care of. While it is the newest of the learned professions illuminating engineering is attracting more attention than all the rest combined just now. Although the world's first. Illuminating Engineering Society was organized in New York as recently as January, 1906, it already has more than a thousand THIS PHOTO. TAKEN BY THE LIGHT FROM THE EYE. BRINGS OUT It helps to explain why the Plaza Theater. Chicago, was rescued from fail- of fact, it was merely their outraged nerves being soothed by scientifically HALLWAY OF THE NEW PUBLIC SERVICE BUILDING, NEWARK. N. J.. ILLUMINATED BY MOORE TUBES. DRAUGHTING ROOM PROPERLY LIGHTED. Cooper Hewitt lamps are better than daylight for some purposes. Note the unusual detail. members, every one of whom seems to be as busy as the proverbial nailer. The parent society has its headquarters in the handsome building which good St. Andrew Carnegie bestowed on the engineering profession in general, while there are flourishing sections in Boston, Philadelphia, Chicago and elsewhere. England followed our example by organizing the first illuminating engineering society in Europe in 1908. These apostles of the new gospel of light are creating such a furore that when Johns Hopkins University, coöperating with the Illuminating Engineering Society, arranged a series of thirty-six lectures on the subject last summer the average attendance was two hundred and fifty. It certainly was high time for the illuminating engineer to appear. The capital invested in the manufacture of gas in the United States amounts to $1,600,000,000, while that invested in the UNDER THE BALCONY DIRECT LIGHTING IS STILL USED IN THE PLAZA THEATER. Note the difference between this part of the interior and the remainder, which is illuminated by the indirect system. ignorance of the elementary principles of lighting seem appalling. As recently as two years ago the only thing considered was the specific density of illumination, regardless of anything else. But now it is understood that the quality and direction of light, quite as much as the quantity, have a most important effect upon the eye. The color of the light, too, is carefully considered in adapting illumination to the specific purpose for which it is required. There is a great difference in the color of artificial lights. The old carbon filament incandescent lamp, the flaming arc and the plain gas flame give a yellow light, the mercury lamp a greenish light, the tungsten incandescent lamp a so-called white light, while the Moore vapor tube approximates daylight so closely that it can be used in matching colors with perfect satisfaction. Each form of light is adapted to some particular use. It is the business of the illuminating engineer to select the right light for each purpose and see that it is used in the proper way. The problem of artificial lighting, as defined by Dr. C. P. Steinmetz, the distinguished electrical engineer in a recent address before the Illuminating Engineering Society, comprises the consideration of the source of light, the flux of light issuing from it, the distribution of the light flux in space, or the density of the light flux in space, particularly at the objects illuminated, the density of the light flux reflected from the illuminated objects and the effect produced thereby on the eye. This latter consideration leaves the field of physics and enters the realm of physiology, which is not as amenable to exact experimental determination as the former, hence available knowledge is far more limited than in physical science. One of the main difficulties of illuminating engineering is that IMPROPERLY LIGHTED SILK RIBBON LOOM IN A PATERSON, N. J.. MILL. Ordinary incandescent lights by which the operatives work all day were used to take this photograph. Compare with illustration opposite production and distribution of electric light is $2,000,000,000. Of the vast sum expended annually for artificial light twenty-five million dollars, at the most conservative estimate, is wasted; for while there has been no lack of able electrical engineers and gas engineers, their efforts have been confined exclusively to the economical production of gas and electric current. Their concern ended when gas of good quality was delivered at the burner and current at the lamp socket. The illuminating engineer devotes his attention to the use of light in contradistinction to its production. Illuminating engineering is rather a complex art, for it embraces architecture, decoration, color effects, optics, physics, physiology, and psychology in addition to the commercial aspects of lighting. While much remains to be learned, the progress already achieved makes recent it embraces two different sciences, physics and physiology. The easiest way to get an illustration of Dr. Steinmetz's definition is to walk along a retail street in any ' good sized town until you come to a show window lighted according to the principles of the new art. You will not need to be told when you come to it. Instead of a fringe of naked incandescent lights all around the window obscuring everything in it and hurting your eyes so that you avert your head and hurry past, the sources of light are completely concealed. The only light coming from the window is that which is reflected from the objects viewed, and that is the proper way. No illumination is now considered satisfactory if the eye is exposed to the direct rays of a bright light, for this is both uncomfortable and inefficient. THE SAME LOOM PHOTOGRAPHED BY THE COOPER-HEWITT LIGHT. The human eye is just as sensitive to the difference in lighting as the lens of the camera. In these days when every one has so much to say about efficiency, illuminating engineering is of the first importance. In order that employes may work rapidly and well they should be protected from needless fatigue. About the quickest and surest way to tire out a roomful of people is to flood the room with a uniform light at high intensity. Where work is to be done by artificial light the general illumination should be moderately low with local lights of higher intensity above the work bench or desk. And, by the way, the average desk light or reading lamp is too low. The color of the light, too, plays an important part in tiring people out. Fatigue occurs far more quickly with orange and yellow rays at high intensities than from green and bluish green light like that from the mercury vapor lamp. Nothing equals the bluish white of diffused daylight. In other ways color plays an important part. If there were such a thing as an untidy housekeeper she would doubtless be glad to know that colors resulting from age and dirt may be obscured if not altogether hidden by using a reddish. yellow light like that from a carbon filament electric light or a candle, for these rays harmonize with the typical yellow or brownish shade of dirt. The bluish green mercury light, on the other hand, exaggerates blemishes and dirt, while the white arc light is nearly as bad. Mercury and arc lights are also too harsh and disagreeable for use in the ball room. There the yellow carbon filament is the best. Shadows also have an important part to play. In fact one of the principal aids. in distinguishing objects is the differences in brightness. If there were no shadows but only a perfectly diffused illumination of high intensity it would be hard to see clearly. In order to have |