Management of Light in Illumination. 151 



were necessary to prevent its being thrown out of the 

 lamp by the opening which it was necessary to leave 

 for the air to pass freely in and out of the reservoirs. 

 The most convenient situation for this opening is in 

 the middle of the stopper which closes the passage by 

 which the oil is poured into the lamp; and there I 

 have established it. This stopper is perforated at its 

 centre by a vertical hole of about one tenth of an inch 

 in diameter; and on the top of this stopper, which is 

 flat, there is soldered a thin, hollow, truncated cone, 

 made of tin, half an inch in diameter below, o.i of an 

 inch in diameter above, and three fourths of an inch in 

 height, in the axis of which another smaller truncated 

 cone is placed, in such a manner as to remain* sus- 

 pended in it. This smaller cone is 0.15 of an inch in 

 diameter below, 0.5 of an inch in diameter above, and 

 half an inch in height ; and it is entirely concealed in 

 the larger cone, except only about o.i of an inch in 

 length of its upper end, which comes through the 

 small opening of the larger cone to which it is sol- 

 dered. 



This simple contrivance has proved to be an effect- 

 ual remedy for an accident which embarrassed me for 

 some time. When the lamp happens to receive any 

 violent jolt, the regurgitation of the oil in the circular 

 reservoir is sometimes such as to cause a small portion 

 of oil to be thrown up through the small hole left for 

 the passage of the air in the centre of the brass stop- 

 per ; and, although I had taken the precaution to cover 

 this opening by a vertical narrow tube, near an inch 

 long, the oil was, nevertheless, sometimes forced out of 

 the top of this tube by the air which escaped from the 

 secondary reservoir, on its being warmed by the hand ; 



