Management of Light in Illumination. 197 



in the production of light, the experiments were con- 

 tinued with the larger lamp, and it was found that 

 more light was produced by this lamp in the combus- 

 tion of a given quantity of oil when the lamp was so 

 managed as to furnish 900 of light than when the 

 flame was either longer or shorter. 



When the lamp was burning in such a manner 

 as to produce uniformly 900 of light, the oil 

 consumed in one hour was found to be . . . 560 parts. 



The wax consumed by nine wax candles in fur- 

 nishing the same quantity of light would 

 amount to 900 



When this lamp furnished 800 of light, the oil 



consumed per hour was 515 



Wax required in producing the same quantity of 



light by means of wax candles ..... 800 



When the lamp was forced so as to make it give 

 1000 of light, its flame became very long, and it 

 emitted smoke at intervals, and more oil was employed 

 in producing a given quantity of light than when less 

 light was demanded. 



When 1000 of light were furnished, the expense 



of oil per hour was 669 parts. 



Ten wax candles must have been employed to 

 produce this quantity of light, and they would 

 have consumed of wax 1000 



When this lamp furnished 800 of light, 100 parts of 

 the oil gave as much light as could be furnished by 

 155 parts of wax. 



When the lamp furnished 900 of light, 100 parts of 

 the oil then consumed furnished as much light as 

 could be produced in the combustion of 160 parts of 

 wax. 



But when the lamp was made to give 1000 of light. 

 100 parts of the oil then burned or dissipated produced 



