The stand for the lamp is admirably supplied by the ordinary camera tripod.
For the illuminant we may select any good acetylene cycle lamp.
For this a holder is made of 1/2-inch wood, according to the sketch shown
in Fig. 189. The width of all the four parts should be about 2 inches
greater than the front glass of the lamp. B and C should be sufficiently
far apart to allow the lamp to rest on the rim above the carbide chamber;
and the front, A, should be at least an inch higher than the top of the
lamp glass.
[Illustration: FIG. 189.--Signalling lamp with quick-moving shutter.]
The hole cut in B must be so situated as to bring the front of the lamp
close to the front of the holder, so that the greatest possible amount of
light may be utilized. The hole in A should be rather larger than the lamp
front, and, of course, be accurately centred. Mark these two holes off
carefully, and cut out with a pad saw or fret saw.
A socket must be attached to the centre of the underside of the base to
take the camera screw; or, if such a socket is not easily obtainable, a
hole should be drilled in the base to take an ordinary wood screw of good
size, the surplus of which is cut off so as not to interfere with the lamp.
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