I ROM DIFFERENT APPARATUS. o? 



otherwise remain longer in contact with the flame. If tin 

 chimney be removed from (he burner, the flame will be increas- 

 ed to double its former length, yei the light is pale, and the 

 quantity emitted is much less. When the burner is surrounded 

 by the glass chimney, if the wick remain at the same height, the 

 strength of light required can be better regulated by the quail' 

 tity of air admitted, than in any other manner; and for tin* 

 purpose, these lamps should be Furnished with delicate valv< s, 

 and the most intense light will not be found, when the largest 

 quantity of air is admitted. 



The advantage of elevating the temperature of the air. i- 

 demonstrated by the increased intensity of Light, which is pro- 

 duced by the button sometimes used in these lamps. 



VOL. in. 



