IMPROVEMENTS IN ROOF LAMPS SPECIALLY USEFUL FOR RAILWAY CARRIAGES, APPLICABLE ALSO TO ELEVATED LAMPS GENERALLY
Year: 1877

page_text: LETTERS PATENT to James Nicholas Douglass, of Dulwich, in the County of
Surrey, Civil Engineer, for the Invention of "IMPROVEMENTS IN ROOF LAMPS
SPECIALLY USEFUL FOR RAILWAY CARRIAGES, APPLICABLE ALSO TO ELEVATED
LAMPS GENERALLY."
Sealed the 15th May 1877, and dated the 13th January 1877.
PROVISIONAL SPECIFICATION left by the said James Nicholas Douglass
at the Office of the Commissioners of Patents on the 13th January 1877.
JAMES NICHOLAS DOUGLASS, of Dulwich, in the County of Surrey, Civil Engineer.
"IMPROVEMENTS IN ROOF LAMPS SPECIALLY USEFUL FOR RAILWAY CARRIAGES,
APPLICABLE ALSO TO LAMPS GENERALLY."
This Invention has for its object improvements in roof lamps, especially useful
for railway carriages, and consists of a combination of cylindrical glass lenses and
prisms surrounding the flame of the lamp, and so arranged as to condense and
deflect by refraction and reflection, or by either of these agents, or both, the light
(now usually wasted on the ceiling and the upper part of the compartments of the
carriages) for the convenience and comfort of passengers occupying the same.
The lenses and prisms are so arranged as to form part of the glass or basin
usually attached to railway carriage roof lamps, or the lenses and prisms may be
made to surround and enclose the said glass or basin; or, in some cases, the usual
glass or basin may be used surrounded by lenses and prisms for the purposes above
set forth.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by the
said James Nicholas Douglass in the Great Seal Patent Office on the 12th
July 1877.
JAMES NICHOLAS DOUGLASS, of Dulwich, in the County of Surrey, Civil Engineer.
" IMPROVEMENTS IN ROOF LAMPS SPECIALLY USEFUL FOR RAILWAY CARRIAGES,
APPLICABLE ALSO TO LAMPS GENERALLY."
This Invention has for its object improvements in roof lamps for railway car-
riages, and elevated lamps generally of similar character, and consists in the peculiar
combination of cylindrical glass lenses and prisms surrounding the flame of the
lamp, and so arranged as herein-after specially set forth, described, and illustrated
[Price 411

page_text: by the accompanying Drawings as to condense and deflect by refraction and reflec-
tion, or by either or both, the light (now usually wasted on the ceiling and the
upper part of the compartments of the carriages) for the convenience and comfort
of passengers occupying the carriage.
The lenses and prisms are so arranged as to form part of the glass or basin
usually attached to railway carriage roof lamps, or the lenses and prisms may be
made to surround and enclose the said glass or basin.
Having thus far described the nature of the said Invention, and incidentally
intimated in what manner the same is to be performed, or carried out in practice,
I will now proceed (aided by the accompanying Drawing) to further and particularly
describe and ascertain in what manner the same is to be performed or carried out
in practice, that is to say :-
A is the flame of the lamp.
B, the oil receiver, from which the oil is conveyed to the burner by the usual
channels.
C is the outside case of the lamp.
D is the glass or basin formed with the lenses and prisms, as shewn. The glass
or basin is suspended from the outside casing (C) of the lamp, as shown at d, d.
E, the reflector placed as usual above the light.
The rays of light from the flame strike against the side of the basin and the
prism (D) and lenses (D2), which are are so formed (as shown) as to deflect the
rays of light (as shown by the dotted lines e) downwards. The rays that strike
the reflector (E) are deflected down vertically, the bottom of the basin being plain,
as shown.
By these means it will be seen that the whole of the rays of light are deflected
downwards, and thus the waste of light on the ceiling and upper sides of the com-
partments, as in the ordinary lamps, is overcome.
The central focal point of the flame is represented at F, and from this focus the
rays (e) issue.
The rays will, as will be understood, blend together when dispersed by the lenses
and prisms, as shown.
G represents the horizontal focal plane. Above this plane, as will be seen, the
ascending rays strike against the prism (D') and lenses (D2), and below the plane
the rays fall and strike against the lenses Dx and the lenses of form shown at 13
below the focal plane, the whole being deflected as shown.
The whole of the rays blend together, and form a beam of light, which is thrown
or deflected, as herein-before set forth and described.
Having now particularly described and ascertained the nature of the said Invention,
and in what manner the same is to be performed or carried out in practice, I
hereby declare that I claim the said Invention, substantially as the same is herein-
before set forth and described, and illustrated by the accompanying Drawing.
In witness whereof, I, the said James Nicholas Douglass, have hereunto set
my hand and seal, this Ninth day of July, in the year of our Lord One
thousand eight hundred and seventy-seven.
Witness,
T. MORGAN,
Secretary,
Inventors' Patent Right Assn., Ld.,
21, Cockspur Street, S.W.
JAS. N. DOUGLASS. (L.S.)