CERTAIN IMPROVED LEN- TIG GLASSES FOR LIGHTING AND REFLECTING OR REFRACTING
Year: 1857

page_text: LETTERS PATENT to Louis Emile Ossian Degrand, Gentleman, of Paris,
in the French Empire, for the Invention of "CERTAIN IMPROVED LEN-
TIG
GLASSES FOR LIGHTING AND REFLECTING OR REFRACTING."
PROVISIONAL SPECIFICATION left by the said Louis Emile Ossian
Degrand at the Office of the Commissioners of Patents, with his
Petition, on the 25th February 1857.
I, LOUIS EMILE OSSIAN DEGRAND, Gentleman, of Paris, in the French
Empire, do hereby declare the nature of the said Invention for "CERTAIN
IMPROVED LENTICULAR GLASSES FOR LIGHTING AND REFLECTING OR REFRACTING,',
to be as follows:-
My lenticular glasses are composed of striated glass. It is well known
that while this glass cannot be seen through yet it admits light, and has
therefore been used for blinds, and in doors and windows, instead of painted
or ground glass. The effect produced by these glasses is dependant upon
the deviation of the rays of light caused by the stria of waves in the glass,
and the direction followed by the rays of light on leaving the glass depends
upon the form of the striae or waves.
Now, my Invention consists in constructing lenticular glasses of striated
glass, and in shaping the striae or waves and the glasses according to the
direction in which rays of light or heat are to be reflected or refracted.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Louis Emile Ossian Degrand in the Great Seal Patent
Office on the 31st July 1857.
TO ALL TO WHOM THESE PRESENTS SHALL COME, 1. Louis.
EMILE OSSIAN DEGRAND. Gentleman, of Paris, in the French Empire, send
greeting.
WHEREAS er most Excellent Majesty Queen Victoria, by ler Leuters
Patent, bearing date the Twenty-fifth day of February, in the year of our
Lord One thousand eight hundred and fifty-seven. in the twentieth year of
Her reign, did, for Herself, Her heirs and successors. give and grant unto me.
the said Louis Emile Ossian Degrand, Her special licence that 1. the said
Louis Emile Ossian Degrand, my executors, administrators, and assigns, or
such others as I, the said Louis Emile Ossian Degrand, my executors, admi-
nistrators, 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 United
Kingdom of Great Britain and Ireland, the Channel Islands, and Isle of Man,
an Invention for "CERTAIN IMPROVED LENTICULAR GLASSES FOR LIGHTING AND
REFLECTING OR REFRACTING," "pon the condition (amongst others) that I, the
said Louis Emile Ossian Degrand, my executors or administrators, by an
instrument in writing under my, or their, or one of their hands and seals,
should particularly describe and ascertain the nature of the said Invention,
and in what manner the same was to be performed, and cause the same
to be filed in the Great Seal Patent Oflice within six calendar months next
and immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Louis Emile Ossian Degrand, 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 thereof, reference being had to the Drawings hereunto
annexed (that is to say):-
This Invention relates to the production of lenticular glasses which are
formed with striated, corrugated, or waved surfaces. The Invention includes
the various forms and applications of the glasses as well as the mode of their
manufacture.
It is well known that although glass corrugated, striated, or waved cannot
be seen through. yet it admits light, it has therefore been used instead of
blinds, and as a substitute for painted or ground glass. This sort of glass
too may be so made, and its waves, striae, or corrugations so formed, as to

page_text: serve as powerful lenses or reflectors for lamps. lights. &c.. and as mirrors.
And as the effect produced by these glasses upon the rays of light which
penetrate or fall upon them, and the direction of the reflected or refracted
light depends upon the form of the lens or glass, and upon the form of the
waves or striae upon its surface. the object of the present Invention is to
construct lenticular glasses of corrugated glass, and in forming the corrugations
And the glasses of such shape or shapes as to produce any required effect
of refraction or reflection on light or heat.
The Drawings accompanying the present Specification, with the following
references and demonstrations, will make the nature and details of the Invention
perfectly intelligible.
Fig. 1 represents a diametral section of a corrugated lens producing the
same effects as an ordinary lens of the form called plano-convex. The surface
of this lens may be regarded as a surface of revolution generated by the
revolution of the colored figure about A. B. as an axis. This lens is of course
circular, as in Figure 2. and has one side quite plane, while the opposite side
is striated or corrugated. as the Figure 1 shews.
Figure 3 is a 'corrugated cylinder of glass. formed by the revolution of the
Figure 1 about the line C. D. which is parallel to the straight side m. n. of
the Figure. This glass is analogous to those used in lighthouses for producing
a fixed light.
Again, causing this same generatrix to move parallel to itself and in a
direction perpendicular to its own plane, a form of glass. Fig. 4. is obtained.
which, combined with that represented by Fig. 3, is capable of producing
exactly the same calorific or luminous effects as the circular corrugated lens,
Fig. 2. Figures 1 and 4. on a scale of half the full size. represent a lens
of 10 centimetres (about four inches) focal distance. 8 millimetres (about
inch) thick, and 16 centimetres (about 6 inches) broad. I must be under-
stood, however, that glasses of this kind can be made of any required dimensions
and focal length. If they are desired so large as to be inconvenient or
impracticable in manufacture in a single piece they can be made in separate
parts.
Glasses or lenses of the forms known as plano-concave. double concave, or
double convex can be formed in a precisely similar manner.
Mirrors or reflectors are produced by the use of glass properly striated.
Figure represents the section of a plate of glass plane on one side and
corrugated on the other. The plane of the section is perpendicular in the
straight striae. The faces of the striae are all equal and at right angles to
one another. Now, suppose a ray of light to fall on the plane face of the

page_text: plate in the line m. n, it penetrates to the interior of the glass without
refraction, then undergoes a first total reflection from the face a. b. then a
second from the face a. c, and finally escapes from the glass in the line
1. m. which is parallel to n. m, but the direction of the reflected ray is
exactly opposite to that which it had before entering the glass. A reflector
of this sort will reflect all light striking it in the direction of the normal.
and without permitting any to pass through it: in fact such a reflector acts
precisely like an opaque mirror. It will be seen that such plates of glass
are well fitted under some circumstances to serve the purpose of blinds.
Employed in glazing greenhouses and conservatories they will arrest the
direct rays of the sun without producing on the inside a darkness sufficient
to injure the plants. As reflectors for the inside of carriage and railway lamps
this sort of glass plate is almost as effective as plated copper mirrors. and
has not the liability to tarnish, which belongs to these latter.
If, instead of a plane sheet of corrugated glass, the material be adapted to
a curved surface, whether cylindrical or spherical. having such a section as
represented in Figure 6, the reflection of normal rays will hold for such a
surface as well as for that already treated. And thus, if a reflector so formed
he illuminated by a light placed in its axis or centre, all the rays of light pro-
ceeding from such a central or axial source will strike the mirror in the
direction of its normal at every point of incidence, and will. therefore, as has
already been seen. be reflected back in a direction exactly opposite to that in
which it at first proceeded. These mirrors or reflectors. unsilvered and un-
plated. produce in a greater or less degree the same effects which are attained
by the use of metallic or silvered glass reflectors.
In the practical manufacture of these various striated lenticular glasses
Iwo methods may be employed-first. the ordinary casting process: second.
stamping. by means of dies or moulds, when the glass has been sufficiently
softened by heat to allow it to receive under pressure the required impression.
In either case the first thing to be done is to make a mould precisely corre-
sponding to the form which the glass is required to receive. When the casting
process is adopted, a raised border or rim is made round the edges of the
corrugated mould. corresponding to the thickness to be given to the glass; a
mooth cover. of the form designed for the face of the glass, is then made;
then the quantity of melted glass corresponding to the volume of the casting
is taken from the crucible of the factory and transferred to the mould, the
cover is then put on, and the two pressed together with great force. Both
parts of the mould are, before the casting is commenced, heated to a very
high temperature.
The glass is afterwards annealed in the ordinary way

page_text: If. on the contrary, the stamping method be adopted. plaies of glass are
taken having exactly the dimensions designed for the finished glass lens or
reflector. These are placed in a furnace, so constructed as to raise the material
to the temperature proper to soften the glass to the required degree without
the glass becoming fouleil or injured by the ashes or cinders, and while the
glass is still in the furnace the proper mould, which is itself heated to an equal
temperature. is applied from above. An apparatus is arranged traversing the
interior of the furnace, by means of which a very greal force is brought to act
upon the die or mould. This process is like that generally used for striking
medals, except that in the present case it is conducted in the interior of a
furnace heated to a very high temperature.
This last and new method of making lenticular glasses has this advantage.
that it permits in the production of small lenses the use of the fragments of
plate, and, even of common window glass; it enables me too to make very
thin lenses of any extent of surface. It is only necessary for this object
that the striae or corrugations impressed upon the thin glass be made suffi-
ciently fine. In all cases the stamping has the advantage of the common
casting process. inasmuch as it produces lenses of a more uniform thickness.
As to the construction of the moulds, it is my intention that they should he
made in the turning lathe with the best possible tools, and that that metal
shall be employed in their construction which in the progress of the glass
manufacture shall be recognized as the best adapted to give a polish to the
surface of the glass cast in contact with the said. metal. At present the mate-
rial should be cast iron. of the best quality, and all the moulding surfaces
should be polished with the greatest possible care. If need be. these surfaces
may be electro-plated with a light coating of silver. gold. or platinum. to
preserve their polish and prevent oxidation. It is necessary that this coat-
ing should be very thin, in order that when the moulds are heated the
difference of expansion of the two metals may not cause them to separate.
The following are the principal applications of the present Invention:-.
First, lighting the public streets and thoroughfares.-If we suppose a
horizontal plane to pass through the flame of a gas lamp which lights the
public streets, it is easy to see that the rays of light whose courses lie below
that plane alone are effective in illuminating the street or road. All those
that radiate above this said plane are useless. and are lost. so that the useful
effect of the lamp would be almost doubled if a reflector were used to change
the direction of those upward rays and send them down to do service in illu-
minating the road and footpath.
The principal modes in which I apply my Invention to attain this desirable

page_text: object will be seen by Figures 8. 10, 12. and 14. The arrangement repre-
sented by Figures 8 and 9 is intended for streets of considerable breadth.
This system of apparatus is composed of half such a cylinder m, n, p, as is
represented in Fig. 3. having its striated side turned towards the street, and of
two portions of plane lenses perpendicular to the direction of the street 1. m,
p. q. This arrangement increases the power of the lamp to light the breadth
of the street. and strengthens the light upon the pavement.
The second arrangement. Figures 10 and 11. is composed of a conical lens.
which completely encircles the upper part of the lamp, and is adapted for
lamps placed in the middle of squares, crosses. avenues. &c.. where they are
required to light up the neighbourhood on all sides. The conical form is
adopted to produce the depression of the luminous rays, and it is applicable to
the lamp represented in Figures 8 and 9. as well as to all others which are
intended to light up, any considerable circumference.
The third arrangement, Figures 12 & 13. is designed for streets of ordinary
breadth. It is composed of two plane lenses, with circular striae. These are
intended to shed strong streams of light up and down the street. As these
lamps are ordinarily arranged along the side of the street on the fronts of or
near the houses, care must be jaken that these lenses be so inclined that their
axes be directed towards points in the streel midway between the lamp lo
which the lenses belong and those next it.
A fourth arrangement is represented by Figures 14 & 15 This method
may be conveniently adopted in large squares and areas which can only be
lighted round their peripheries. In this case. the rays proceeding above the
horizontal plane are thrown down by means of a reflector placed at the upper
part of the lamp and besides this, at the lower part of the lamp a plane lens
p. q. r. s. is placed so as to direct a stream of light towards the middle of the
square, place, or area.
:
Figs. 8. 10, 12, and 14, exhibit also various methods of deflecting the
upward ray's of the lamp, and rendering them useful in illuminating the street
or path below. The simplest is that represented in Fig. 10, which consists of
a spherical cap a, b, c. having a section like that represented in Fig. 6. already
described. This striated piece of glass forms a sperical reflector, at the centre
of which the flame of the lamp is situated. and the surface of which reflects
towards the ground all the light which falls upon it.
In Figure 8 the corresponding glass is striated or corrugated on both sides,
and the striae are so formed and combined as to produce an interior and total
reflection. These are technically called catadioptric glasses. On examination
of one of the elements a, b, c, of this reflector it will be seen that a ray of light

page_text: from the flame entering the prismatic element by the face a, c, undergoes a
total reflection from the face a, b, and escapes through the face b, c, al the
desired inclination towards the ground. The coloured section k, l, turning
round a vertical axis, generates a conical refractor, of which d, e, 1, 9, is a
partial elevation, and the same section revolving about a horizontal axis
generates the plane lens, of which h, d, g, l, is a partial elevation.
It is by means of this same generating section, turning about a horizontal
axis, that the glass a, b, c, d, with which the lamp represented in Figure 12 is
glazed, is produced.
At Figure 14 is represented, at the upper part of the lamp, a reflector
having striae on one face only, and disposed, like the catadioptric rings in use
in lighthouses, with this new feature, that it is a sort of catadioptric system
of steps.
Examining an element a, b, c, of the section, it will be seen that the light
impinging on a, b, penetrates the glass to be reflected by the face m, n, and
then escapes by the face a, c, with the desired inclination. In order to save
all the light with this method there must be two plates of glass, as m, n,
and m, n. This section may turn about a vertical axis, as in Figure 14,
generating a conical reflector, or it may turn about a horizontal axis, and so
generate a lens.
It need scarcely be stated that, independently of the particular applications
and methods of arrangement herein-before specified, the striated lenticular
glasses may be applied publicly or privately, and in any desirable combination,
to change either by reflection or refraction, or by both, the direction of
luminous rays of a flame or light in any required manner. In all cases the
glasses take the place of the ordinary glazing of street lamps, &c.
The second application is to railway signal lamps of all kinds.-The striated
glasses of equal size produce a better effect and throw a stronger light
than the reflectors commonly in use in railway lamps; they can be manu-
factured at a cheaper rate, are much lighter, and at the same time more handy
and more easily preserved. Figures 20, 21, 22, and 23 represent a few of
these signals.
The first, Figures 20 and 21, is an engine lamp, of a circular form, com-
posed simply of a circular lens and of a reflector.
Figures 22 and 23 represent a signal lamp for the hand; it is glazed on
three sides with lenses, each accompanied by a piece of coloured glass, so that
red, green, and white siguals are united in the same, lamp. This method of
doubling the lens with plane coloured glass deserves special mention. At first
sight it may appear that dust lodging on the striae of the lenses would make

page_text: the difliculty of preserving them bright too great. Such, however, is not the
case, as this dust can be easily and quickly removed by the use of a brush.
But to make this still better, when the lens is doubled with the plane glass,
à little cement placed round the edges will keep all dust from the striae and
reduce the cleaning to that of two plane surfaces. It must be understood
that this same arrangement may be adopted not only in railway lamps, but
also in lamps and lights furnished with striated lenses or reflectors, whatever
their purpose or object.
The various kinds of lamps used on railways are too numerous to be
individually enumerated here. It is enough to state that the striated lenses
may with advantage be substituted for every species of reflector in ordinary
use in connection with these lamps.
The third application is to carriage lumps.-The common metal reflectors
used in carriage lamps are generally costly, while they speedily get tarnished,
and so become more or less non-effective. By substituting the striated
lenticular glasses for these reflectors, the lamps are made less expensive, easier
to keep clean and bright, more convenient, and their light more powerful.
Figures 16 and 17, 18 and 19, represent two of these lamps, one square, the
other hexagonal. The rationale of their construction may be readily under-
stood by inspection.
With equal advantages these glasses may be applied to any or every other
form of carriage lamp, whether it be that of the cylinder or of any sort of
prism. It will be necessary in all cases that the flame of the candle or lamp.
be placed in the focus of the lenses employed in glazing the lamp.
The fourth application is to screens, shades, blinds, &c.-These glasses
may be substituted for the porcelain and opaque glass shades in common use
for various kinds of lamps.
Again, globes of striated glass may be made for lamps of the form repre-
sented in Figure 7, which is so formed as to be globe and shade in the same
piece.
i
The fifth application is to glasses for lighthouses.-This important application
of the present Invention claims more attention and more explanation than
any of the preceding.
It is well known that the glasses of lighthouse apparains and beacons
manufactured after the process of Augustin Fresnel are composed of as many
separate pieces as there are rings, and that each of these rings, after having
been roughly cast, is put in the lathe, where it receives its proper form and
polish. This process, while it gives the rings great precision of form, is ex-
cessively expensive, and makes it necessary to give the rings considerable

page_text: thickness in order that they may stand the turning and polishing which they
undergo; it causes also large opaque joints where the various pieces are
cemented together.
I propose to substitute for this process my own mode of manufacturing
striated glasses. By this method the glass is obtained either in one single
piece or in a very small number of pieces at first cast, and afterwards the
pieces are placed in the lathe merely to perfect their polish. in which latter
process the layer of material which is removed is imperceptibly thin. These
pieces when cast have a polish of their own, which may be improved by
exposure to the heat of an active fire, so melting their surfaces. But the
polish so obtained is inferior to that obtained by turning; and glasses like
those for beacons and lighthouses, intended to produce powerful effects,
should receive the best possible polish, which can only be obtained by the
cutter and the lathe.
The area
A com
Figure 25 represents in dotted lines the diametral section of the lens in
present use. having a focal length of 92 centimetres (about 3 feet).
bounded by drawn lines and coloured green is that adopted by me.
parison of these two sections will shew the economy of material given by the
new process.
:
Figure 28 and 29 represent a cylindrical glass and an annular lens, each
subtending from its focus an angle of 45 degrees. The first is obtained by the
revolution of the section, Figure 27, about a vertical axis. and the second by
the revolution of the same section about a horizontal axis. In these Figures
the red lines mark the joints of the lens proper to the old process, and the
blue lines denote the joints which necur in the lenses manufactured by me.
It will be seen from these lines that the joints in the old are much more con-
siderable and extensive than in the new process proposed by me, so that while
the lens represented in Figure 29 would by the old method be composed of
27 pieces, it is made by the new process in not more than 1 pieces, a number
which will doubtless be reduced as the art of casting and moulding glass
progresses.
Figure 2 represents in dotted lines A, B. C, the old section of a cala-
dioptric ring, and in drawn lines the section of the improved ring. It will be
seen that the sides of the latter. which are parallel to the side A. B, of the
former, will produce the same effect as that side, except in so far as regards a
little loss of light corresponding to the lines drawn in red.
Figure 30 represents a series of catadioptric rings for a lighthouse of the
first order, and shews that considerable economy of material is thereby
produced, and the glasses of course rendered much lighter. Glasses generated

page_text: in various ways by this form of section may be adapted to either permanent
or occulting and flashing lights.
Figure 31 is the vertical projection of a catadioptric glass for a permanent
light. The red lines represent the stops in the old system and the black lines
those in the new.
For calculating the forms to be given to the striae or waves of the improved
glasses. I prefer the formulae of Fresnel because of their accuracy.
Where
the striae or waves are very numerous. I do not propose to calculate them
separately. but to construct a line of centres of curvature. like that shewn in
Figure 26. The points A. B. C. D. &c., on this line are first ascertained by
calculation, and any intermediate points may of course be readily obtained for
corresponding intermediate striae or waves.
The construction of the moulds employed for making the improved glasses
may be simplified by disposing the striae or waves in equal groups with their
refracting faces parallel to one another. This process may be further simplified
by substituting the chords for the small ares of circles which form the surfaces
of the striae.
And having now described the nature of the said Invention, and in what
manner the same is to be performed, I declare that I claim,-
First, the manufacture of lenticular glasses of striated, waved, or corrugated
glass, as herein-before described.
Secondly, the application of lenticular glasses formed of waved. striated. or
corrugated glass to the manufacture of public lamps, railway lamps, carriage
lamps. hand lamps, screens, shades, blinds, and apparatus or lanterns for
lighthouses, as herein-before described, and represented in the Drawings
hereunto annexed..
In witness whereof, I, the said Louis Emile Ossian Degrand. have here-
unto set my hand and seal, this Fifth day of July, One thousand eight
hundred and fifty-seven.
L. E. O. DEGRAND. (..s.)