blaizolite
The lantern has a cylindrical body which encloses a system
of seven plano-convex lenses and six mirrors surrounding the lamp-bulb. Six of the lenses are mounted round the lamp, and opposite to
each of these is placed a mirror which can be so adjusted that the light can be reflected at any desired angle. The seventh lens is mounted
in front of the bulb and between it and the diffusing glass front. The six mirrors are hinged at their inner edge, the outer edge being
fastened to a quadrant passing through the back plate, where it is secured at the desired position by wing-nuts. Each mirror may also be
rotated through slots in the back plate in the plane of the latter. The lantern is enclosed by hinged doors at the back and front, the hinges
being so arrraged that any door may be reversed. The door frame carries a sheet of hammered cathedral glass, which effects the
requisite diffusion. Used extensively for the illumination of large exterior areas such as railway sidings,
colliery works, quarries, harbours, etc. They were used experimentally for street lighting in 1928 as part
of the Sheffield Experiment.
