(orad7 
XLIV. 
A METHOD OF INCREASING THE POWER OF CONTINUOUS 
LIGHTHOUSE LIGHTS. By JOHN R. WIGHAM, M.R.LA., 
Member of the Council of the Royal Dublin Society. 
[Read DecemBer 19; Received for publication DecempeEr 20, 1894; 
Published Jury 22, 1895.] 
From this title it will be seen that I do not propose to bring 
under the notice of the Society any new lighthouse illuminant. 
On a previous occasion I brought before this Society what I believe 
was then, and still és, the most powerful lighthouse light, viz. the 
intensity burner with the giant lens. On this occasion I propose 
to describe a method of increasing the efficiency of any lighthouse 
light, not by increasing the power of the illuminant, but by 
altering the method of the application of the optical apparatus 
with which it is associated, so as to give continuity to revolving 
lights and greater power to fixed lights. Notwithstanding the 
many names by which lighthouse lights are distinguished, there 
are practically but two classes into which they can be divided, viz. 
fixed lights, and revolving or flashing lights. The light of “ fixed 
lights” is generally transmitted through refracting belts and 
prisms. On placing a burner in the focus of the apparatus the 
vertical light is refracted in parallel rays, the horizontal light being 
allowed to proceed to every part of the horizon without reflection 
or refraction. The effect of this fixed light apparatus at a short 
distance (say about 100 feet) is to produce a column of light the 
height of the apparatus and the breadth of the burner. It is, of 
course, immensely less powerful than the light which is trans- 
mitted by annular lenses by which the light is parallelized, both 
vertically and horizontally, into beams, transmitting to the observer 
all the light from the burner which falls upon them. In order 
to send these beams to every part of the horizon the lenses must 
of necessity be caused to rotate, and this constitutes the revolving 
light of lighthouses. 
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