IMPROVEMENTS IN THE MANUFACTURE OF LAMP GLASSES, APPLICABLE TO RAILWAY CARRIAGE AND OTHER the
Year: 1857

page_text: LETTERS PATENT to Thomas Hart, of Watts' Terrace, Old Kent Road, in
the County of Surrey, Agent, for the Invention of "IMPROVEMENTS IN THE
MANUFACTURE OF LAMP GLASSES, APPLICABLE TO RAILWAY CARRIAGE AND OTHER
the County of Surrey, Agent, for the Invention of "IMPROVEMENTS IN THE
MANUFACTURE OF LAMP GLASSES, APPLICABLE TO RAILWAY CARRIAGE AND OTHER
LAMPS."
Sealed the 13th November 1857, and dated 27th May 1857.
PROVISIONAL SPECIFICATION left by the said Thomas Hart at the Office
of the Commissioners of Patents, with his Petition, on the 27th May,
1857.
I, THOMAS HART, of Watt's Terrace, Old Kent Road, in the County of
Surrey, Agent, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN THE MANUFACTURE OF LAMP GLASSES, APPLICABLE TO RAILWAY
CARRIAGE AND OTHER LAMPS," to be as follows:-
The object of my improvements in the manufacture of lamp glasses,
applicable to railway carriage and other lamps, is to construct these glasses in
such a manner, that the light from the burner, instead of being dispersed and
diffused over parts where it will be useless, will be concentrated and thrown"
into parts where it is or may be required. The Invention is particularly
intended to be applied to railway carriage lamps, as well as to hall and other
lamps in which the light is required to be thrown downwards.
The object of the Invention is effected by constructing the glass which
encloses the lamp of a lenticular form, so that the rays of light in passing

page_text: through the glass may be refracted from a direct line, and thereby con-
centrated.
The glasses which enclose the lamps of railway carriages are, as is well
known, of a globular form, and of the same thickness, instead of which I
propose to construct them internally either with flat or conical surfaces,
which, in combination with the convexity of the external surface, will form a
kind of lens, which will refract the light as it passes through, as is well known.
The bottom of the glass inside is made flat, so as to form an ordinary
plano-convex lens immediately under the burner.
Sometimes I find it convenient to pierce the bottom lens at the centre for
the purpose of admitting air for ventilation, or for the introduction of a burner
should hydrogen gas be employed for the purpose of illumination.
An obvious modification of the above is the adaptation of one glass within
another, the space between them being filled with some liquid, which will
refract the rays of light:
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Thomas Hart in the Great Seal Patent Office on the
26th November 1857.
-
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS
HART, of Watts's Terrace, Old Kent Road; in the County of Surrey, Agent,
send greeting:
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-seventh day of May, in the year of our
Lord One thousand eight bundred and fifty-seven, in the twentieth year of
Her reign, did for Herself, Her heirs and successors, give and grant unto
me, the said Thomas Hart, Her special license that I, the said Thomas
Hart, my executors, administrators, and assigns, or such others as I, the
said Thomas Hart, my executors, administrators, and assigns, should at
any time agree with, and no others, from time to time and at all times
thereafter during the term therein expressed, should and lawfully might
make, use, exercise, and vend, within the United Kingdom of Great Britain
and Ireland, the Channel Islands, and Isle of Man, an Invention for
"IMPROVEMENTS IN THE MANUFACTURE OF LAMP GLASSES, APPLICABLE TO RAILWAY
CARRIAGE AND OTHER LAMPS," upon the condition (amongst others) that I, the
said Thomas Hart, by an instrument in writing under my hand and seal,
should particularly describe and ascertain the nature of the said Invention,

page_text: and in what manner the same was to be performed, and cause the same to
be filed in the Great Seal Patent Office within six calendar months next and
immediately after the date of the said Letters Patent.
NOW KNOW. YE, that I, the said Thomas Hart, do hereby declare the
nature of my said Invention, and in what manner the same is to be performed,
to be particularly described and ascertained in and by the following statement,
reference being had to the Drawing hereunto annexed, and to the letters and
figures marked thereon (that is to say) :-
The object of this Invention is so to construct lamp glasses, that, instead of
diffusing the light (from the burners to which they are applied) equably over
the surrounding space, 'they will concentrate it and throw the concentrated rays
into parts where it is specially required.
The Invention is more particularly applicable to railway carriage lamps, and
to other lamps where the light is required to be thrown downwards. I propose
to attain this object by constructing the glass which encloses the lamp of a
lenticular form, so that the rays of light in passing through the glass may be
refracted from a direct line, and thereby concentrated.
The glasses which enclose the lamps of railway carriages are, as is well
known, semi-globular, resembling somewhat a bowl in shape, and the glass is
of the same thickness throughout; but in manufacturing such, glasses accord-
ing to my Invention, I propose to form on their inner surface flat or convex
parts, which, in combination with the convexity of the external surface, will
form a kind of lens, which will refract the light as it passes through, as is well
known.
In the accompanying Draving I have shewn in section various forms of
glasses suitable for railway carriage lamps, and made according to my Inven-
tion, the object in all the cases being to direct the rays of light downward
towards the floor of the carriage.
Fig. 1 is the section of a railway carriage roof lamp glass with an annular
plano-convex lens only; Fig. 2 is a section. of a railway carriage roof lamp
glass with annular and bottom bull's-eye plano-convex lens; Fig. 3 is the
railway carriage roof lamp glass as fixed, shewing the inclination of the rays
of light from the lamp within it; Fig. 4 is the section of a glass with double
convex, annular, and bull's-eye lenses; Fig. 5 is the section of a glass, with
plano-convex annular lens, open at bottom for the admission of a gas burner;
Fig. 6 is a sectional view of a perforated bull's-eye lens. The part of the
glass from a to b, in Figures 1 and 2, will, by reason of its flat internal surface,
form an annular lens, and the part from a to a in Fig. 2 will form a central
plano-convex lens immediately under the burner. In Fig. 4 the parts from

page_text: a to bas well as from a to a are made convex, so as to form with the outside
four double convex lenses. All these forms of lamp glass I propose to produce
by casting them in an iron or other metal mould.
When adapting the Invention to hall and other lamps, I may find it con-
venient to pierce the bottom of the glass for the purpose of admitting air
for ventilation, and also for the introduction of a gas or other burner when
that is required. This form of glass will be understood by referring to
Figures 5 and 6.
An obvious modification of the above is the adaptation of a glass bowl
flattened or concaved in parts within a globular shaped glass, and filling the
space between them with some liquid which will refract the rays of light.
I would here remark that, although in the Drawing I have shewn all the
glasses as perfectly plain and unornamented, I sometimes propose to orna-
ment the upper part above the lenses, either by cutting, pressing, or coloring
designs thereon. The nature of the ornament must, of course, be left to the
taste of the manufacturer..
Having now explained the nature of my Invention of improvements in the
manufacture of lamp glasses, I wish it to be understood that I claim forming
them with annular and other shaped lenses, in the manner and for the purpose
above described.
In witness whereof, I, the said Thomas Hart, have hereunto set my hand
and seal, the Twenty-third day of November, in the year of our Lord
One thousand eight. hundred and fifty-seven.
Witness,
J. W. MOFFATT,
66, Chancery Lane.
THOMAS HART. (L.S.).