332 



THE INDIA RUBBER WORLD 



February 1. 1921 



THE DIFFERENT KINDS OF ELECTRIC LAMPS 



All electric lamps may be divided into two classes: those which 

 produce light from an incandescent glowing solid, and those which 

 produce light from an incandescent vapor. To the lirst class 

 belong all forms of arc lamps, and electric "bulbs," or filament 

 lamps. Of the latter the two different forms of tungsten filament 

 lamps are the only types that need be considered today. To the 

 second class belong the two types of mercury vapor lamps, the 

 one in a long glass tube, commonly known, from the name of its 

 inventor, as the Cooper-Hewitt lamp, and the other, a short tube 

 of pure quartz, known generally as the quartz lamp. 



These two classes of lamps arc radically different mechanically, 

 but the important difference— the most important fact in the whole 

 subject of industrial lighting— is that the light from the filament 

 lamps has a continuous spectrum (contains all the colors of the 

 rainbow) while the light from the Cooper-Hewitt (.mercury 

 vapor) lamp has a line spectrum (contains only a few colors). 

 The importance of this difference will be made clear after we 

 have studied the structure and action of the visual organs. But 

 let this be kept constantly in mind : the thing we see by is light, 

 and there are two kinds of light now available. Differences in 

 lamps are only incidental, and of very little consequence. 



When we come to the subject of globes and reflectors, we are 

 confronted by the mountain which, after prodigious labor, brought 

 forth a mouse. Their number is legion, and the opportunities 

 which they afford for mathematical juggling are endless. The 

 literature of the subject is filled to overflowing with "papers" and 

 discussions on this' exhaustless topic. What it all amounts to 

 in industrial lighting can be better shown later on, when we come 

 to the consideration of actual problems ; it will then appear that 

 the matter is largely what Professor James called an "t-laboration 

 of the obvious." 



SUMMARY 



The applied science of illumination does not belong among the 

 branches of engineering. 



Industrial lighting should be in charge of the production mana- 

 ger, who should either personally superintend it, or place it in 

 the hands of a responsible subordinate. 



The scientific principles of illumination are divided into two 

 classes; physical, those which deal with the production, distribu- 

 tion and measurement of light ; p.sychophysical, those which deal 

 with the construction and operation of the visual organs. 



Light has two physical qualities, intensity, or brightness, and 

 color. 



Sunlight is made up of all the colors of the rainbow, which 

 form the solar spectrum. All glowing solids give a light having 

 a similar spectrum which is a continuous band of colors. Glowing 

 gases give a line spectrum, i.e., a spectrum consisting of lines of 

 color separated by lines or bands of darkness. 



The spectrum of a light can be produced by passing it through 

 glass prisms, which separate the colors. 



Intensity is measurable. The unit is the candle-power, which 

 is the intensity of light given out by a standard candle (now 

 actually a standardized electric lamp) in a horizontal direction. 



Intensity of light varies inversely as the square of the distance 

 from the source. 



Illumination is the result of light falling on a surface. It has 

 the quality of intensity, which varies inversely as the square of 

 the distance of the surface from the light source, and is measured 

 in foot-candles. 



The foot-candle is the intensity of illumination on a surface one 

 foot from a standard candle. 



Light falling upon a surface is partly reflected and partly ab- 

 sorbed. The percentage of reflected light is the coefficient of 

 reflection of the surface. 



Reflection is of two kinds, specular, or regular, and diffuse, or 

 irregular. Specular reflection produces images of objects and 



gives bhine or gloss to surfaces. Diffuse reflection gives surfaces 

 a mat or dead finish. 



Surface brightness is the inteiisity of light emitted by a surface. 

 It is measured by the lambert, which is the brightness of a surface 

 of one square foot which emits light of 2 c.-p. The mille-lambert 

 is .001 of this unit. 



The physical efficiency of a lighting system is the amount of 

 light received on an imaginary plane 30 inches from the floor, 

 divided by the number of watts used in generating the light, and 

 is thus expressed in lumens per watt. 



Electric lamps are of two classes: arc and filament lamps, which 

 give a continuous spectrum, and vapor lamps, which give a line 

 spectrum. 



Accessories in the form of globes and reflectors are used with 

 lamps to modify the distribution of light. 



In the ne.xt article we will discuss the elements of vision ; that 

 is, the construction and operation of the eye. 



UNITED STATES IMPORT DUTIES ON RUBBER GOODS 



The following list has been taken from a schedule prepared by 



the Bureau of Foreign and Domestic Commerce solely for statis- 

 tical purposes. This schedule will not be deemed authority for 

 deciding, in doul)tUil cases, the rate of duty properly chargeable 

 upon any imported article named therein. 



Oass Tariff Unit of Rate of 



No. Paragraph Quality Duty 



CRUDE SUBBER, ETC, 



JO.OII 1 Wild rublier pound Free 



-'O.OJI Plantation rubber pou»d Free 



_'O,0.il 513 Guayule pound Free 



-'U,04l Jelutcng (Pontianak) pound Free 



J0.U51 J Balata pound Free 



20,<Jtil 502 Gutta percha pound Free 



21,31: ) ,, Crude chicle pound $0.15 



21,321 f •' Chicle, refined, dried, stained pound $0.20 



SCRAP AND RECLAIMED RUBBER 



20. Ill ) e 1 ^ Reclainied rubber pound Free 



.?0,I21 (' Scrap cr refuse pound Free 



RUBBER SUBSTITUTES 



20.311 ),„, Crude pound 10% 



20,212 / °' Advanced by manufacutre pound 15% 



RUBBER MANUFACTURES 



oS'iS,' /ICO Druggists' sundries pound 15%. 



20,671 J iOS Rubber tires and tubes number 10% 



20,911 262 Belting of cotton or other vegetable 



fiber and rubber pound 15% 



20,991 ( -^ Other manufactures of rubber pound 10% 



20,995 ;-'°= Of gutta percha pound 107o 



20,999 369 Of vulcanized or hard rubber... pound 25% 



MANUFACTURES CONTAINING RUBBER 



n.425 ] Garters, suspenders, braces of cotton.. nunibc* 25%. 



31,426 i 262 Tire fabrics of cctton square yard 25% 



33,995 j Garters, tire fabrics, suspenders, braces, 



made of vegetable fibers and rubber. yard 25% 

 36,991 29^ Webbings, suspenders, braces, of wool 



and rubber pound 35% 



.'7,315 316 The same, of silk and rubber.... pound 45%. 



RUBBER AND OTHER WATERPROOFED CLOTH 



39.161 254 Cotton or other vegetable fiber and 



rubber square \ar(i 25%. 



39.162 318 Silk, chief value square yard 45% 



39.163 288 Wool, chief value square yard 35% 



.19,164 30S Mohair, chief v.iint square yard 40% 



WATERPROOF CLOTHING 



39.181 256 Cotton or other vegetable fiber and 



rubber pound 30% 



39.182 317 Silk, chief value pound 50% 



39.183 291 Wool, chief value pound 35% 



39,tS4 308 Mohair, chief value pound 40% 



39,185 278 Flax, hemp or ramie and rubber pound :i5% 



6n.;i94 114 Insulated wire pound 15% 



60,898 124 Card clothing, not attached to carding 



machines or parts of, manufactured 



with plated wire with rubber-face 



cloth square foot 35%. 



61,394 138 Rivets, studs, for non-skid automobile 



tires pitind 20% 



93,192 157 Fountain pens gross 25%^ 



94 '13 368 Golf, tenuis, foot basket and baseballs, 



chieflv of rubber pound 10% 



94,314 369 The same, chiefly of vulcanized rubber. pound 25%. 



