196 Management of Light in Illumination. 



300 of light, that lamp was now laid aside ; and these 

 researches were continued with the two more powerful 

 lamps No. 2 and No. 3. 



When these were made to furnish each 400 of light, 

 the quantities of oil consumed in one hour were as 

 follows : 



By the lamp No. 2 320 parts. 



By the lamp No. 3 361 



Wax required for producing the same quantity of 



light ' . . 400 



Here again we find that the smaller light has still the 

 advantage over the larger. 



When 500 of light were furnished, the quantities of 

 oil consumed were : 



By the lamp No. 2 357 parts. 



By the lamp No. 3 405 



Quantity of wax necessary to produce the same 



quantity of light 500 



The smaller lamp still continues to maintain its 

 superiority, but we shall soon find that the larger one 

 will get before it. 



When both lamps were so regulated as to produce 

 each just 600 of light (equal to that of six wax can- 

 dles), the quantities of oil consumed per hour were 

 found to be as follows : 



By the lamp No. 2 ... 474 parts = 512 grains Troy. 

 By the lamp No. 3 ... 441 = 476 

 Quantity of. wax necessary 



for producing the same 



light 600 =648 



As the smaller lamp could not be made to furnish 

 much more than 600 of light, it could no longer be 

 compared with the larger ; but, in order to find out 

 how much farther the economy of oil could be carried 



