63G 



THE INDIA RUBBER WORLD 



Februahv 1, 1921 



principles, justil'ics this assumption. The ultimate results of an 

 engineer's work exist in material structurcs^in railways, bridges, 

 machines, power plants, mnie shafts, etc.; the ultimate result of 

 a lighting installation e.xists in the minds of those using the 

 light; its success is measured by the efficiency with which the 

 visual organs, of which the brain is an essential part, perform 

 their functions. In plain words and few, the final question asked 

 of any method of lighting is: How well can you sec by it? The 

 basis of any rational science of ligliting is therefore to be found 

 in psychology, rather than in physics and mathematics, which are 

 the fundamentals of all branches of engineering. So we shall 

 have to seek still further for the proper source of authority on 

 the practical use of light. 



The end and aim of industrial lighting is perfectly definite and 

 sharply defined ; it i.^. to enable the workman to see to do his 

 work. Without light he can do nothing. With the best of light 

 he can do all that his muscular strength and skill are capable of 

 performing. Between these limits there are all degrees of efh- 

 ciency. The output of the workman thus depends directly upon 

 his ability to see; or, as the scientist would put it, the output of 

 any given operative is a function of his visual impressions. The 

 answer to our question should now be clear : the person by what- 

 ever title designated, who is responsible for the output of any 

 assembly of workmen, should prescribe the kind of light and 

 method of its use for each and every operation. 



LIGHTING BELONGS TO PRODUCTION MANAGEMENT 



Lighting is a part of production management. This definite 

 assignment of the subject to its .proper place in industrial organi- 

 zation would ot itself be a decided step toward reducing it to a 

 practical science, and rescuing it from its present position in no 

 man's land, where it is kept busy dodging the knocks aimed at it 

 from all quarters. 



Having thus placed the responsibility for the lighting in thf 

 department where it rightfully belongs, the duty rests with the 

 general management to assign a particular individual to take 

 personal charge of the matter. Makeshift lighting, which char- 

 acterizes 90 per cent of the industrial installations, and which 

 reduces output anywhere up to 40 per cent, is a direct result of 

 the failure to place the responsibility and authority in some one 

 person, directly concerned with production. All of the technical 

 data necessary to handle the problem in a practical, scientific 

 manner can be easily mastered by anyone having a common 

 school education. 



1 shall attempt to give this data in plain English, stripped of 

 all unnecessary scientific verbiage, and omitting all that does not 

 have a direct practical bearing on the subject. The reader who 

 takes the trouble to become familiar with what is given can 

 investigate his own special problems in a scientific manner, and 

 pass intelligent judgment on all schemes proposed by sales engi- 

 neers who are inclined to embellish their arguments with high- 

 sounding technical terms, and particularly if they find their pros- 

 pect is unable to contradict them. 



ANALYSIS AND CLASSIFICATION OF THE SUBJECT 



The first ^tcp m the scientific treatment of any subject is 

 analysis, taking it apart to discover the elements, or fundamental 

 principles of which it is composed. Now, as to industrial light- 

 ing: there is light; there are the mechanical contrivances for 

 producing light, classed under the general title of lamps, which 

 are often equipped with globes and reflectors for modifying the 

 light; there are the objects on which the light falls and which it 

 illuminates; there is the eye which receives light from the ob- 

 jects; and the brain, which gives the sensation of seeing. 



The next step is classification. In this case the elements in- 

 volved fall into twc classes : the production of light and its con- 

 version into illumination, and the action of the visual organ in 

 producing tho mental sensation of seeing. 



Two different sciences will, therefore, be called upon to fur- 

 nish the facts and theories, the judicious application of which 



will enable us to secure the most satisfactory results. These two 

 sciences are physics, dealing with light, and psychology, dealing 

 with vision. Lighting, as a science, is thus a branch of psycho- 

 physics. 



But let not the practical, intelligent production manager, su- 

 perintendent, foreman, or workman take fright at these high- 

 sounding names. All that he needs to know of these sciences to 

 enable him to handle his lighting problems understandingly is 

 quite within his comprehension, as I hope to show. 



NATURE OF LIGHT 



Light is a form of energy which acts through space by means 

 of wave motions. It is of the same nature as the energy used 

 in wireless telegraphy, the only difference being in the size of the 

 waves. The general properties of waves may be observed from 

 tliose on water. Thus, if you drop a pebble into a pond of still 

 water, you will see a series of waves spread out in the form of 

 concentric circles, each circle enlarging uniformly until it reaches 

 the shores of the pond. Any given point in a wave moves out 

 from the center along a radius of the circle. If you bring your 

 hands together sharply you set up a wave motion in the air, 

 which you recognize as a sound ; but in this case the waves spread 

 out in the form of constantly expanding spheres, and so proceed 

 in all directions in space, any given point in a wave traveling 

 along a radius of the sphere. If you heat a piece of iron suffi- 

 ciently hot it sends out in a similar manner a series of waves 

 which spread in all radial directions, and which, if they enter the 

 eye, produce the sensation which we call light. These waves are 

 motions in a substance — or more accurately a medium, for it is 

 quite different from what we know as substance, which is sup- 

 posed to fill all space, and scientifically is called ether. It is in 

 this ether that the wireless electrical waves move. Ether-waves 

 are commonly called radiations. 



Referring again to the water waves : the motion of the wave 

 over the surface must be clearly distinguished from the motion of 

 the water, which simply rises and falls with a definite rhythm. 

 Recall now the waves on a large body of water ; measuring from 

 crest to crest they exhibit very great differences, from the huge 

 dead-swell to the tiny ripple. This distance from crest to crest 

 is called the tivizv length. Also, the waves show equally great 

 differences in their height, or distance from the bottom of a 

 trough to the top of a crest. This is called amplitude of the wave ; 

 the greater the amplitude the greater the amount of energy in 

 the wave; on water high waves result from strong winds. You 

 will recall further that waves of all sizes run over the water at 

 the same time. 



THE TWO MEANINGS OF LIGHT 



We can now proceed with consideration of those waves, or radia- 

 tions, which are called light because they produce the sensation 

 of light on entering the eye. Note carefully now that the word 

 light has tw'o very different meanings, the one being an effect upon 

 Ihe mind, and the other the form of energy (radiations) which 

 causes this mental sensation. These are, respectively, the psycho- 

 logical and the physical meanings of the term. Waves may differ 

 in length and in amplitude. In light-waves variations in ampli- 

 tude produce differences in intensity, or flux density, in the radia- 

 tions, and differences of brightness in visual sensation. Differ- 

 ences in wave-length produce the variations of sensation which 

 we call colors. The colors have a natural order, thus : beginning 

 with the longest waves, the color is deep red ; as the waves become 

 shorter the color changes to brighter red, then to yellow, green 

 and blue, the blue becoming fainter until it begins to show a mix- 

 ture of dull red forming a violet, and finally becomes a faint 

 crimson which soon fades entirely out This succession of colors 

 is called the visible spectrum and corresponds to the scale in 

 music. The light of the sun and of all artificial lights with one 

 exception contain all of the colors at once, but in somewhat dif- 

 ferent proportions. Pure sunlight is called white light. Any 

 variation from the proportion of colors found in this standard 



