Wicuam—Petroleum as an Illuminant for Beacons, etc. 379 
time during which the lamp is to be maintained: (in the case of 
this particular lamp thirty-one days). It is constructed on the 
bird-cage fountain principle, and has a cock, or valve, to enable the 
oil to be cut off whenever necessary. The lamp receives oil from the 
above fountain as it is required for the maintenance of the light. 
The wick is passed over a roller which is surmounted by a combus- 
tion cone and surrounded by lenticular apparatus ; one end of the 
wick being conveyed up in an oil-tight tube, with holes in its sides as 
it passes through the body of the lamp, and the other passing down 
through a tube standing above the level of the oil in the lamp and 
soldered or secured at the lower end. A circular float is placed in 
a cylindrical tank fixed to the bottom of the lamp and filled with 
oil. When the lamp is first lighted, this float is at the top of 
the tank and is attached by means of hooks or loops to the 
wick. The oil from the tank is permitted to drop through 
a valve or cock supplied with a cotton core through which, 
drop by drop, at such speed as may be necessary, the oil 
descends into the receiver, bringing with it the float and the 
wick which is attached to it. When, at the end of a month or 
such other period as may be desired, it is necessary to replenish 
the lamp with oil, the receiver is emptied and the fountain and 
tank refilled. 
Buoys.—Such a lamp as fig. 1 is suitable for permanent beacons 
or perches, but when a light on this principle is required for buoys 
a smaller lamp is used, and the supply of oil, instead of being 
overhead as in the beacon lamp, is underneath the burner. 
This arrangement is adopted mainly to keep the centre of 
gravity low. In the case of buoys it is necessary to fix the 
lamp upon swivels or gimballs, so that however great may be 
the motion of the sea, the lamp may be kept practically level. 
Arrangements are also made by divisions in the oil-chamber 
by which, when it is for a moment brought out of level by 
the motion of the sea, the oil is prevented from flooding the wick, 
because of its having but slow access to it during the time of the 
passing of the wave, after which its proper level is again main- 
tained. 
A full-sized working example of this lighted buoy lamp, with 
gimball arrangement, by which it may be kept practically level, 
was exhibited, and is shown in fig. 2. 
