612 



THE INDIA RUBBER WORLD 



JlNF. 1, 1921 



any given amount of illumination. One lumen gives an intensity 

 of one foot-candle on one square foot of surface. One thousand 

 lumens will therefore light 100 square feet with an intensity of 

 10 foot-candles, or 200 square feet with 5 foot-candles, or 66 

 square feet with 15 foot-candles, and so on. It will be easy to 

 remember, and sufficiently accurate, to consider that mercnry- 

 vapor light costs $3.50, and tungsten light $5 per 1,000 lumens, 

 with current at 1 cent. Increasing the cost of current increases 

 the cost of tungsten light somewhat more than it does of mercury- 

 vapor light. To be exact, with current at 2 cents, the latter light 

 will cost $5.63 and the former light, $7.82 per 1,000 lumens per 

 year. 



Xo figures are given for cleaning and repairs for the reason 

 that the conditions determining these costs are too variable to 

 admit of any estimation of value. So far as replacements are 

 concerned tlie mercury-vapor lamp will require attention once in 

 three years, according to the guaranteed average life of tubes ; 

 the tungsten unit will require attention three times a year for the 

 same purpose. For cleaning, each will, of course, require equal 

 attention. The mercury-vapor lamp contains an operating mech- 

 anism, which will sometimes need attention and repairs. On the 

 whole, this may be considered a fair offset for the labor expended 

 in the more frequent renewals of the tungsten units ; so that 

 this item reduces to a fifty-fifty proposition as between the two 

 types of lamps. 



A CONVENIENT METHOD OF STATING THE COST OF 

 ILLUMINATION 



The true basis for measuring the cost of light, considered sim- 

 ply as a form of power, is by taking the product of lumens into 

 hours, just as electricity is measured by watt-hours, or for prac- 

 tical use, by 1,000- watt or kilowatt-hours. As the costs per 1,000 

 lumens just given were for 3,000 hours' use, the cost per 1,000- 

 lumen-hour — which we may very properly call the kilolumen-hour^ — 

 will be .003 of the amounts given, or 1 cent per k.l.h. for the 

 mercury-vapor, and V/2 cents per k.l.h. for the tungsten light. 



It is interesting to use these rates to figure the cost of illumina- 

 tion for the individual workman. Suppose he occupies lOO square 

 feet of space, and is supplied with an intensity of 10 foot-candles — 

 which is sufficient for first-class work under most conditions ; 

 he will require one kilolumen, and in an eight-hour day will use 

 8 k.l.h. costing 8 cents for the mercury-vapor, and 12 cents for 

 the tungsten light. The practical reader may amuse himself by 

 figuring what percentage this is of the workman's wages, and 

 of the value of the materials which he handles. Lastly, he may 

 consider the difference between furnishing the workman 10 foot- 

 candles and 5 foot-candles — from 4 cents to 6 cents a day — 

 evaluated in terms of wages, and in spoiled, or defective work. 

 He will then have an example of that principle in logic known 

 as "reductio ad absurdum," which may be freely translated as a 

 "damned absurdity." 



In conclusion : It may appear to the reader who has never 

 given particular attention to the technical points involved in mod- 

 ern lighting that we have drawn the subject out to a tedious 

 length. To this I may reply that only those points have been 

 considered which have a direct and important bearing on the 

 subject, and these as briefly as consistent with a fair compre- 

 hension of the subject. I may also remark, that besides numerous 

 matters not touched upon in these articles, whole volumes have 

 been written upon most of the topics we have considered, not to 

 mention numerous papers and discussions before scientific societies. 

 The one simple conclusion is, that lighting in modern industrial 

 institutions is not a mere matter of hanging up a lamp here and 

 there, but is a problem of first-class importance in its relation to 

 production costs and general welfare. 



SUMMARY 



The efficiency of a lighting installation is to be estimated from 

 two standpoints : the effect upon the output of labor, and the cost 

 of producing the light. 



The effect of light on the output of labor depends upon (1) the 

 quality of the light, (2) intensity of illumination, (3) direction of 

 light on work, and (4) freedom from conditions which reduce 

 visual efficiency. 



The choice of the kind of light-unit will depend upon the first 

 and last of the above conditions. 



The lay-out, or location of the units, will be determined by the 

 last three conditions. 



There are two ways of making a lay-out: so as to light the 

 room, or light the job. 



Lighting the job consists of machine lighting and bench lighting. 

 It differs from room lighting in that the dircclioii of the light is 

 of prime importance. 



Room and bench lighting are easily arranged in accordance 

 with the simple engineering data given. 



The mechanical efficiency of a lighting system is the relation 

 of cost to the quantity of light used. It is most conveniently com- 

 puted in 1,000-lumen (kilolumen) hours. The items to be con- 

 sidered are : interest and depreciation of installation, electric cur- 

 rent, repairs and renewals. 



The cost of illumination is less than 2 per cent of the wages 

 of those working under it. 



RUBBER TIRES AND THE PROPOSED VEHICLE LAW 



A favorable impression is being made throughout the country by 

 the draft of the proposed uniform vehicle law indorsed by the 

 Motor Vehicle Conference Committee of The Rubber Association 

 of America, Inc., the American Automobile Association, the 

 Motor & Accessory Manufacturers' Association, Inc., the National 

 Automobile Dealers' Association, and the Trailer Manufacturers' 

 Association of America. The committee, in preparing the tenta- 

 tive measure, considered not only the road builder, road user, and 

 the vehicle maker, but also the carrying capacity of the road, and 

 the general welfare of the public, and the fees to be imposed are 

 to be in lieu of all taxes. The committee will do its best to have 

 the proposed law adopted as fully as possible in the forty-eight 

 states. 



Taking into account the fact that rubber-tired vehicles are less 

 harmful to roads than diose with metal tires, the fees for regis- 

 tration, etc., are much less for the former than the latter. Thus. 

 a motor vehicle with pneumatic tires would pay 25 cents per 100 

 pounds gross weight of vehicle and load, one with solid rubber 

 tires, 35 cents, and one with iron, steel, or other hard tires, 50 

 cents. The same schedule would apply to tractors, while the rate 

 for horse-power would be 25 cents additional, applicable to all 

 classes of vehicles aforementioned. For trailers and semi-trailers 

 the weight scale ranges as follows: Pneumatic tires, 15 cents per 

 100 pounds; solid rubber tires, 25 cents; iron, steel, or other hard 

 tires, 35 cents. Motorcycles and motorcycle sidecars would be 

 taxed uniformly $5 each. 



In computing the weight of trucks, it is provided that "no 

 vehicle having a load of over 800 pounds per inch width of tire 

 upon any wheel concentrated upon the surface of the highway 

 (said width in the case of rubber tires to be measured between 

 the flanges of the rim") .shall be operated in any state." 



Vehicles equipped with pneumatic tires of gross weight of not 

 over 7,000 pounds and carrying seven passengers would be allowed 

 to go 30 miles an hour on open country highways, 20 miles on 

 suburban streets, and 15 miles on city streets. Other pneumatic- 

 tired vehicles carrying a weight of from 6.000 to 28,000 pounds 

 would be restricted to 25, 20 and IS miles in the same order. 

 Solid-tired vehicles of 4,000 pounds gross weight would be allowed 

 to make 25, 20 and 15 miles, but those of 8,000 pounds. 20, 18, and 

 12 miles. Vehicles of 12.000 pounds would lie limited to 18, 15, 

 and 12 miles, and of 16.000 pounds, 16. 15. and 12 miles. All over 

 that weight, and up to 28.000 pounds, would be held down to 

 15. 15. and 12 miles an hour. 



