April I, 1921 



THE INDIA RUBBER WORLD 



483 



Artificial Lighting in the Rubber Industry — IV' 



By E. Leavenworth Elliott 



General Conditions to Be Considered in the Lay-out 



IN LAYING OUT a licatiiig system the first question is : What 

 temperature must be maintained? Having decided this, the 

 amount of heat required is found l)y considering the volume 

 of space to be heated ; then, the amount of heat given off by a 

 given radiating surface, such as a steam coil, being known, the 

 total area of radiating surface is easily determined. In figuring 

 out the quantity of heat required certain general conditions other 

 than the cubic contents of the room must be considered, such as 

 the rate of change of air for ventilation, the miniinum outside 

 temperature, the conductivity of the walls, etc. The influence 

 of these factors is more a question of judgment based on ex- 

 perience than of 

 mathematical calcula- 

 tion. Lastly, having 

 determined the total 

 amount of radiating 

 surface, the method 

 of locating it so as 

 to secure the most 

 uniform temperature 

 through the space 

 must be worked out. 

 The lay-out o f 

 lighting installation is 

 a somewhat similar 

 problem. The first 

 question is : What 

 degree, or intensity, 

 of illumination is re- 

 quired? This will 

 naturally depend upon 

 a number of condi- 

 tions, such as the 

 character of the ma- 

 terials, the accuracy 

 of the work, the color 

 of surrounding walls, 

 etc. It is not so gen- 

 erally known that the 



A Good Example of Mill LkjHiing bv Looper-Hevmit L.\mi'S. Tut LA.\n'> Ceinc 

 Located to Give the Best Illumination on the Machines 



quality of the light is also a large factor 

 in this determination; but before we discuss this in detail it will 

 be well to consider the general problem. 



Having decided upon the intensity of illumination needed, the 

 size and location of the light-units may be determined ; and from 

 this data the total quantity of light, and the corresponding amount 

 of electric current required, can be reckoned. 



It is a curious fact that, in all the scientific investigations that 

 have been carried out, and all the theoretical work that has been 

 done to put the use of light on an engineering basis, all answers 

 to the first, and most important question, have been merely so 



Illumin.^tion Required for Textile Processes 



Foot-candles 



Light Dark 



Cotton goods goods 



Opening and lapping 2-6 2-6 



Carding 2-6 2-6 



Drawing frame 2-6 2-6 



Roving, spooling, spinning, etc 3-9 3-9 



Warping 2-6 2 6 



Slashing 2-6 2-6 



Drawing-in 3-9 3-9 



Weaving 3-9 3-9 



Dyeing 3-9 3-9 



'Continued from The Ikdia Ribber World, March 1, 1921, pages 412-416. 



many broad guesses. Extended lists of operations with the in- 

 tensity of illumination required for each have been published; 

 but the wide dilTerences in the figures are in themselves suf- 

 ficient evidence of the uncertainty of their authority. As to what 

 precise methods were used to determine them the authors are 

 discreetly silent. The preceding tabulation of operations pertain- 

 ing to another industry may be cited as an example. 



It is a familiar fact that the eye can function through an 

 enormous range of light intensities. From dim starlight to full 

 sunlight represents a difference of more than a million to one 

 in hrichtness. The question is not whether an operative can 



see to work, but can 

 he see to work with 

 his greatest efficiency? 

 Reduced to a scientific 

 basis, which is also 

 the common-sense ba- 

 sis, the rule is this: 

 Such a degree of 

 illutnivation must be 

 provided, the quality 

 of tlie light and all 

 other conditions af- 

 fecting vision being 

 considered, that the 

 muscular motions 

 zvhich depend upon 

 sight for their guid- 

 ance can be made 

 zvith the greatest 

 speed and accuracy of 

 ■which the individual 

 is capable under the 

 circumstances in each 

 case. 



Or to put it the 

 other way around : 

 the workman must 

 not be hindered in the slightest degree by the illumination. The 

 problem is to find the minimum intensity required : this can be 

 exceeded by several hundred per cent without interfering with 

 the desired result; but to use an excess of material or power is 

 not good engineering — in fact, it is not engineering at all, but 

 only guesswork The extent to which excess is avoided meas- 

 ures the value of the engineering skill applied. 



Seeing involves the recognition and discrimination of the various 

 parts and features of the objects seen. In a general way the 

 effectiveness of sight depends upon the amotmt of light reflected 

 froin the object; in other words, its average surface brightness. 

 It is like timing a photographic exposure, which is based upon 

 the general brightness of the field. It needs no elaborate sci- 

 entific formula to tell you that more light is necessary to see 

 dark-colored objects plainly than to see light-colored ob- 

 jects; also, that more illumination is needed to discriminate 

 objects between which there is little contrast in brightness. 



Recent experiments show that the intensities formerly given 

 for different classes of work are much too low, at least in the 

 cases where sharp vision is required. The most accurate and 

 reliable experiments of this kind, the results of which have not 

 yet been published, show that, in the case of average sharpness 

 of vision, such as that required to read printing the size of this 



