Management of Light in Illumination. 143 



The circular reservoir is composed of two pieces of 

 tin, a and q, formed under the hammer, which are 

 soldered to each other and to the tube b. That which 

 forms the upper part of the reservoir is convex : the 

 other, q> is in the form of the large end of a trumpet. 



The oil passes from this reservoir into the burner 

 through a very small hole made in the side of the 

 tube b, which opens into the interior of the short 

 tube /. 



The greatest diameter of the circular reservoir is 

 two inches and a half ; and its depth, measured from 

 the level of the highest part of its sloping bottom, is 

 0.8 of an inch. The vertical height of this .sloping 

 bottom q is also 0.8 of an inch, which makes the 

 greatest depth of this reservoir 1.6 inch ; but the 

 lower part of it being very narrow holds very little 

 oil. 



The hoop h, which serves as a screen to the air- 

 holes in the tube b, is three fourths of an inch in width 

 and 1.7 inch in diameter. 



Before this hoop was used, the flame of the lamp 

 was liable to be deranged, not only by sudden blasts 

 of wind blowing directly into these air-holes, but also 

 by sudden jerks accidentally given to the lamp in 

 carrying it ; but the hoop has been found to be an 

 effectual security against both these accidents. 



The rings k and z, Fig. 2 (Plate VI.), which have the 

 appearance of being introduced for mere ornament, 

 serve two important purposes. They prevent the air 

 from being forced into the air-holes in such a manner 

 as. to derange the flame in moving the lamp very sud- 

 denly, or with a jerk, either upwards or downwards ; 

 and they also prevent the air within the tube b from 



