152 Management of Light in Illumination. 



but, since I have substituted the double cone in lieu of 

 this vertical tube, this accident has never happened, 

 and a bare inspection of the figure is sufficient to show 

 that it never can happen. 



Any small quantity of oil on being thrown up into 

 the conical chamber must necessarily spread over the 

 bottom of it, from whence it will afterwards descend 

 slowly ; and the air that may happen to follow it imme- 

 diately into the conical chamber will pass through it 

 and escape by the small interior cone, which is evi- 

 dently out of the reach of the oil, and therefore cannot 

 be soiled by it. 



As the brass tube which forms the opening by which 

 the oil is poured into the lamp descends about a quar- 

 ter of an inch below the level of the upper part of the 

 circular reservoirs, it is evident that this reservoir can- 

 not be completely filled with oil, for the air cannot all 

 escape out of it. It would have been easy, by piercing 

 this tube on the side of the circular reservoir in the 

 same manner as it is pierced on the opposite side (to 

 facilitate the escape of the air out of the secondary 

 reservoir), to have opened a passage for the escape of 

 all the air out of the circular reservoir ; but I have not 

 done it, for I conceived that it might be advantageous 

 to leave some air in the circular reservoir, which on 

 inclining the lamp forward escapes, and makes room 

 for the oil which runs out of the trunk of the second- 

 ary reservoir, when the lamp is so inclined. 



This precaution could never be of any use except 

 when the lamp, after having been entirely filled with 

 oil, and before any sensible quantity of it should have 

 been consumed, should be so much and so long in- 

 clined as to endanger the overflowing of the oil in the 



