94 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76 



reduced but slightly, but the efficiency of the tungsten lamp has 

 materially increased and its cost reduced so that it is now possible to 

 obtain, with the ordinary 40-watt lamp 170 candle-hours for a cent. 

 If the gas-filled tungsten lamp were used the amount of light now 

 obtained for a cent would depend upon the size, which, for the 1000- 

 watt lamp, would be 382 candle-hours. 



STATISTICS REGARDING THE PRESENT DEMAND FOR LAMPS 



In the United States there are about 350 million incandescent and 

 about two hundred thousand magnetite arc lamps now (1923) in use. 

 They are increasing about 10 per cent each year. The annual demand 

 for incandescent lamps for renewals and new installations is over 

 200 millions, exclusive of miniature lamps. The use of incandescent 

 lamps in all other countries put together is about equal that in the U. S. 



The average candlepower of standard lighting lamps has increased 

 from 16, which prevailed during the period prior to 1905, to over 60. 

 The average wattage has not varied much during the past twenty-odd 

 years, the average lamp now consuming about 55 watts. This indi- 

 cates that the public is utilizing the improvement in lamp efficiency 

 by increased illumination. The present most popular lamp is the 40- 

 watt size which represents 20 per cent of the total demand. Second 

 in demand is the 25-watt at 18 per cent and third, the 50-watt at 15 

 per cent of the totalin numbers. While the aggregate demand of all 

 the gas-filled tungsten lamps is a little over 20 per cent in numbers, 

 they represent, on account of their greater efficiency and wattage, over 

 half the amount of total candlepower used. In the United States 

 about 85 per cent of all lamps are for the iio-volt range. About 5 

 per cent for 220 volts, 2 per cent for street series lighting, 3 per cent 

 for street railway and 5 per cent for trainlighting and miscellaneous 

 classes of service. 



