This term is applied to prism plates
composed of selected prism lenses which are not tested, polished,
or provided with the Iridian lines on the receiving surfaces.
They are sized and electro-glazed.
This term is applied to the prism plates
composed of prism lenses known in the practice as "Seconds," sized
For the illumination of basements we
manufacture pavement prisms, sometimes called vault lights. These
prisms may be used to produce a certain effect without what is
known as the lucidux, but where a well illuminated basement is
desired, the lucidux, or prism plate placed vertically in the front
end of the basement, so as to receive the light from the pavement
prisms, and transmit it into the basement, is essential.|
The various classes of pavement prisms are
described as follows:
In this pavement prism there is preferably
an oblong top about 5×2¼ inches, with a single lenticular
pendant, both sides of which have been computed on optical principles,
so as to produce the greatest possible degree of illumination, and the
ends of which are prismed, so as to take the light coming from up and
down the street and add it to the quantity of light thrown into the
"Double Prism Extra."
This pavement prism is substantially 4
inches square on top, and has two pendants, varying in length and angle,
and prismed on their ends.
This product is the same as the Double
Prism Extra, except that the pendants are not prismed on the ends.
"Single Prism Extra."
This product is substantially rectangular
on top, 2½×3 inches, with a single pendant prismed on the