Management of Light in Illumination. 155 



the burner, and which is moved by means of a pinion, 

 connected with a button (seen at Fig. i, Plate V.), 

 placed on the outside of the vertical tube, which con- 

 ceals both the burner and the rack, by turning this 

 button to the right or to the left the cylindrical rod is 

 moved either up or down in the burner, as the occasion 

 may require. 



To the upper end of this cylindrical rod is fixed a 

 pair of small elastic nippers with sharp teeth, which 

 hold the lower end of the wick. As long as these nip- 

 pers are within the burner, they are so pressed together 

 by its two opposite sides that they hold the wick very 

 fast ; but, when they are pushed up so high as to come 

 out of the burner, they separate from each other, in 

 consequence of their elasticity. 



When they are in this situation, the remains of the 

 old wick may be removed without difficulty; and the 

 end of the new wick being put in their place, in caus- 

 ing the nippers to descend into the burners, they will 

 necessarily draw the new wick after them. 



The changing of the wick of a lamp has hitherto 

 been a very disagreeable and filthy operation ; but from 

 this description it is evident the wick of this lamp may 

 be changed in an instant, and that there is nothing 

 either difficult or disgusting in that momentary pro- 

 cess. 



Care must be taken in trimming the new wick, first, 

 to make it descend as far as possible into the burner ; 

 then to cut off with a pair of sharp scissors all that 

 projects above the level of the top of the burner ; and, 

 when this has been done, the wick must be raised about 

 i^j- of an inch, and again cut off level with the top of 

 the burner. If this precaution be neglected, the wick 



