520 Scientific Proceedings, Royal Dublin Society. 
placed on beacons and buoys, to guide him under such eireum- 
stances. 
I had the honour of reading a Paper before this Soest on the 
22nd of January last* on a method which I had devised for using 
common petroleum as the illuminant for beacons and buoys, by 
which, at exceedingly low cost, a continuous light can be main- 
tained day and night for weeks or months without the necessity 
for the attendance of a light-keeper. I described in that Paper 
the method by which that form of light was, by means of a 
revolving wick, kept burning for that length of time, without 
attendance. These lights have been permanently adopted in 
Belfast Lough, and other places, and Sane been found suc- 
cessful. 
Lighthouse authorities have determined that, for distinctive 
purposes, two kinds of buoys shall be used in marking rivers, and 
the fairway of harbours and estuaries, viz. conical buoys and can 
buoys; the former to mark the starboard side in entering the river 
or harbour, and the latter the port side. This distinction is, of 
course, useful in the daytime when the buoys are perfectly visible; 
but to establish a similar characteristic distinction at night, it 1s, 
advisable to differentiate the lights on the buoys or beacons, and 
it has been suggested that bright, white lights should be used on 
the starboard side, and red on the port side. 
Some harbour authorities having called upon me to produce an’ 
occulting light which might be suitably used as marking one side 
of a river in contradistinction to fixed lights which might be used 
for marking the other, I devised the lamp here described. It will 
be seen by the simple plan of its construction that we can not only 
have occulting lights on buoys and beacons, but that we can. 
superadd the further distinction of colour, say, besides light and. 
dark alternately, we can have white and red, or red and dark, or, 
green and dark, or amber and dark, or any other variety that se 
be fixed upon. 
In this case the arrangement by means of rotating wicks, by 
which the light is maintained for a month together. without 
attendance, is the same as that described in my previous Paper. 
* Scient. Proc., Royal Dublin Society, vol. viii., Part v., p. 877. 
