Management of Light in Illumination. 117 



difficulty. This reservoir is always removed and taken 

 away and carried into another room, when the illumi- 

 nator is cleaned and replenished with oil. 



The reservoir is a hollow, flat, horizontal ring made 

 of tin (tinned iron), just 0.8 of an inch in thickness or 

 depth, and from i inch to 2\ inches in breadth, accord- 

 ing to the number of burners it is destined to supply. 

 These burners are fixed in its centre in a cluster, as 

 has already been observed ; and their openings above 

 are just i inch above the level of the bottom of the 

 reservoir. Each burner is supplied with oil from the 

 reservoir by a small tube, a quarter of an inch in diam- 

 eter, which, descending obliquely from the inside of the 

 reservoir, enters the burner on one side of it, and at 

 such a distance below its upper extremity as is just 

 sufficient to allow the glass chimney of the burner 

 to be fixed in its proper place. 



Each of the burners is cylindrical; and it is fixed 

 in the axis of a cylindrical tube, 1.88 inch in diariieter 

 and 5 inches in length. This vertical tube receives 

 the glass chimney into its opening above. The wick, 

 which is in the form of a tube, is moved either by a 

 rack or by a vertical endless screw, concealed in the 

 interior of the vertical tube just described, and attached 

 to the side of the burner. When this last contrivance 

 is used, the small horizontal wheel, by means of which 

 the screw is turned, should not be made flat, as they 

 are co7nmonly made, but dishing, in order that the oil, 

 which sometimes finds its way through the collars in 

 which this screw^ turns and runs down slowly on the 

 axis of the wheel, may not be able to spread on the 

 wheel, so as to arrive at its periphery, where it is 

 touched by the finger in turning it, in moving the 



