Descript ion of La mps Mild Concentric Wicks, 38$ 
which receives the oil by a tube sliding in a leather box, which 
may be raised or depressed at pleasure, and which serves to re- 
gulate the level of the discharge of the oil. The superabun- 
dant oil falls into a reservoir placed below the wick, which is 
emptied into the reservoir when the lamp is extinguished. 
It is of the greatest consequence in all these lamps, to regulate 
the current of air. When the chimney is too low, the wick be- 
comes hot, and the flame lengthens and reddens ; and when the 
chimney is too high, the current of air becomes too rapid, the 
flame grows white, but is very small, and experiences a con- 
stant agitation by the too great velocity of the air. 
In order to regulate the velocity of the air, the authors above 
mentioned have used the construction in Fig. £1. Plate VII., 
where F is a second tube, moveable up and down in E, by means 
of the screw nut D, working in a rack GGr, till the flame has the 
proper colour and size. This contrivance, however* was found not 
to answer well in practice, and they afterwards substituted in 
place of it a sort of valve made of iron or platinum, placed at the 
bottom of the chimney, and made to turn upon an axis, so as to 
admit more or less air. In this case, the chimney must be made 
larger than is necessary, and the current has its velocity dimi- 
nished by means of the valve. 
The construction of the burners will be understood from' 
Plate VII. Fig. 18., which is the plan of one with four wicJcSj 
and which is nearly equivalent in its light to twenty of CarceFsr 
lamps. The intervals which separate the wicks, and allow the 
currents of air to pass, diminish a little in width from the cen- 
tral to the external wick. The section of this burner is repre- 
sented in Fig. 19., where C, C', C", C'", (See also Fig. 18.) are 
the racks by means of which each wick may be raised or depres- 
sed. AB is the horizontal projection of the tube, which con- 
ducts the oil to the wicks. L, L, L, L, are small plates of white 
iron, to which the beaks are soldered. „ N is a pressure screw for 
keeping at a proper height the piece MIR, which supports the 
chimney. 
Fig. 21. shows the elevation of the burner with four wicks, 
supporting the chimney. 
Fig. 20. shews the way in which the moveable ring which car- 
ries the wick is placed upon the fixed ring soldered to the rack. 
