Improvements in the Diffusion and Distribution of Light.
Year: 1893

page_text: This Print is in accordance with the Original Specification as it stands after
Amendment (under Section 18 of the Patents, &c. Act, 1883), as allowed by
the decision of the Comptroller General of the 19th day of December 1895.
Date of Application, 12th Oct., 1893
Complete Specification Left, 12th July, 1894-Accepted, 25th Aug., 1894
PROVISIONAL SPECIFICATION.
Improvements in the Diffusion and Distribution of Light.
We, SPIRIDION PSAROUDAKI of 96 Boulevard de Grevelle, Mechanical
Engineer, and ANDRÉ BLONDEL of 2 Boulevard Raspail, Lighthouse Engineer,
both of Paris, France do hereby declare the nature of this invention to be as
follows:-
:-
Our invention has for object -
-to replace the globes, shades, reflectors and
generally envelopes of all forms opal or otherwise actually in use, by others made
of transparent or crystal glass giving the three following results:-
1st. They are shining on almost the whole of their visible surface and receive for
this cause the name of "holophane" (entirely shining).
2nd. At the same time as they diffuse, they distribute the light vertically and
horizontally, according to a required law that seems best in each case of use,
whatever may be the source of light.
3rd. They avoid the loss of light caused by the bars or flutings.
We obtain these three results by means of moulded transparent or crystal glass
substitutes bearing vertical meridian flutings on the inner surface and horizontal
parallel flutings on the outer surface.
Our external flutings are intended to simultaneously distribute and diffuse the
light in the vertical direction; they are very small dioptrical, catadioptrical, or
mixed (both combined) rings, about 5 to 10 millimetres wide, the profiles of which
are not parts of one general distributing profile only, but are independant of each
other; each profile is calculated separately according to the laws of optics, for dis-
tributing its own light within the largest possible vertical angle, and there precisely
according to the law of distribution required for the whole of the light; thence it
follows that almost all the flutings seem simultaneously brilliant, and that the
distribution of light is nearly independant of the source of light placed in the
envelope.
These flutings may be made concave, convex or concavo-convex; they can be
dioptrical or catadioptrical, but the best are our mixed profiles made of two parts
belonging to the two kinds, and either joined directly, or separated by a straight
line, the rays reflected by the catadioptrical part going out through the neighbouring
dioptrical part in the first case or through the straight profile in the second case.
Our internal flutings are intended to simultaneously distribute and diffuse the light
in the horizontal direction. They are calculated for diffusing each its own light
within the largest possible angle of divergence and there precisely according to the
law required for the horizontal distribution. In the most complicated case each of
7.
A

page_text: the flutings should have a disymetrical profile; but under general circumstances it
is only desired to distribute the light uniformly. In that case we employ preferably
a concave or concavo-convex symmetrical profile, calculated for distributing the
light according to the law of cosines, viz. :-for making the intensity of the rays in
every direction proportional to the cosine of the apparent angle of emission of these
rays (as if the envelope were an incadesant black body), in order to make intrinsic
brilliancy as uniform as possible. Moreover in order that the envelope or globe
may appear shining not only in its central part but nearly to the edges, the curve
of the profile must present to the rays a maximum incidence angle of at least 70°;
we do not exceed this proportion for fear of causing losses of light as we will
proceed to explain, and experience has shown us that it sufficient for making the
globe appear "holophane" viz. :-nearly entirely shining. For large lights such
as gas lights, it is even necessary to take a lower angle of maximum incidence.
One of the most important parts of our invention consists in having discovered large
losses of light caused by the flutings, and remedied them. Every ray of light,
when refracted through a horizontal external fluting is also partially reflected into
another direction which is generally too oblique to allow the reflected light to go
out immediately afterwards, so that it will be reflected many times before going
out, and consequently more or less weakened by absorbtion. To avoid this cause
of loss, we adopt a different arrangement in order that the reflected ray may be
sent back after a second reflection, without remaining in the glass; so we limit the
angles of incidence under values of 70° on the internal flutings and 34° to 35° on
the external flutings, in order that proportion of the reflected to the refracted light
may always remain trifling. This latter device has the inconvenience that the
angle of diffusion is limited to a very small value. To make it larger we add to
each dioptrical part a catadioptrical one constituting in that way the varied profiles
spoken of above. In these profiles we took care to put dioptrical parts between
every two catadioptrical ones, in order to leave a free space to the reflected rays for
going out, and to avoid thus a second very important cause of loss viz. :-the return
of part of these rays in the glass. A third cause of loss arises from the reflection
of the rays on the entrance surface of the inner flutings, when these have a convex
profile, for the reflected part of the light is refracted by the neighbouring fluting
into directions more oblique than the directly transmitted rays. We avoid that
inconvenience by employing concave instead of convex flutings, adding if necessary
for the solidity a convex part. For the purpose of grooving the flutings we may
keep this convex part constant on the whole length of the flutings.
Moreover we have devised two systems of moulding process that enable us to
make entire globes or closed envelopes fluted internally and externally in two pieces
cut horizontally or vertically that which has never been done before; the first
system consists of an exterior envelope with hinges, fluted horizontally and a central
core fluted vertically; the second consists of an external envelope with or without
hinges and a central core made of many parts that can be taken to pieces, for
instance of three parts, the central one playing the part of a keystone between the
two others, which can be at will attached to the same platform as the central one.
At last the same system enables us, by simply modifying the profiles of flutings,
to transform into perfect unalterable reflectors either parts of globes and envelopes,
or separate shades or envelopes intended to replace the reflectors actually used.
We obtain this result although the source of light may be of large size or may be
displaced from its appointed position, by means of combined triangular inner and
outer flutings, the edge angles of which are respectively 50° to 55° and 80° to 100°;
for the internal flutings impart to the rays a supplementary deviation that ensures
to the angle of incidence on the external flutings a value always superior to 42°
In some cases, for instance when the source of light is not placed in the centre of a
globe, we prefer to employ for the external profile a curved triangle. We can
combine the total reflection thus obtained with a supplementary effect of diffusion
in order to let the reflector shine on its whole internal surface, by curving slightly
the faces of the prismatic flutings; and to let it shine on its outer surface, by

page_text: adding to each reflecting inner and outer flutings parts more or less important of
our diffusing flutings described above.
S. S. BROMHEAD,
97 Newgate Street, Agent for Applicant.
Improvements in the Diffusion and Distribution of Light.
We, SPIRIDION PSAROUDAKI, Mechanical Engineer, of 96 Boulevard de
Grevelle, Paris, and ANDRÉ BLONDEL, Lighthouse Engineer of 2 Boulevard
Raspail, Paris, in the Republic of France, do hereby declare the nature of this
invention and in what manner the same is to be performed, to be particularly described
and ascertained in and by the following statement :-
Our invention consists principally in replacing the globes, shades, reflectors and
other envelopes for light of all forms, clear, opal or ground fluted or grated actually
in use for diffusing rays of light; by others made of glass or crystal which modify
the direction of the luminous rays by refraction or total reflection in such a way as
to give the three following results.
First, the shining part on these globes or envelopes is not reduced to one point
only, or to a dazzling line, cross, quadrant or star, but extends over almost the
whole of the visible surface; for this reason we call all our productions "holophane"
that is entirely shining.
Second, at the same time by realizing this effect of diffusion they distribute the
light in the surrounding space according to such a given law as seems best in each
particular case, whatever may be the source of the light they contain.
Third, they avoid the loss of light that is so serious in opal globes, and even in
fluted transparent glass, as we shall hereafter explain.
We obtain these three results by means of transparent moulded glass, or crystal,
having vertical meridional flutings on the inner surface, and horizontal parallel
flutings or fluted rings on the outer surface, these flutings being calculated and
impressed in the manner that will be explained hereafter, and this system is the only
one which enables us to get these results.
Moreover the same system enables us, by simply modifying in a suitable way the
profiles of the flutings, to transform into perfect unalterable reflectors either parts
of globes and envelopes, or separate shades or envelopes, intended to replace the
reflectors actually employed. Figures 1, 2, 3, 34 show some examples of this
system.
We will now proceed to describe and explain the principal points that make our
invention a new one, and which we intend to claim accordingly as our own.
First portion of the invention: Particulars of new forms and profiles of the
diffusing flutings.
The first portion of our invention consists in the new system of flutings which
enable us to obtain simultaneously the three above mentioned results, i.e. diffusion
and distribution without loss. This system comprises two parts, the inner and the
outer flutings, which shall be explained independently because we have introduced
new devices for each of them.
First. External flutings. These fluted rings are intended to distribute and
diffuse the light in the vertical direction.
Distribution has been previously realized by others by means of steps, the
profiles of which were parts of one complete profile, (sce M, A, N, Fig. 30,)
calculated for distributing the rays according to the required law, and cut after-
wards into small steps, according to Fremel's method, in order to diminish the
thickness of the glass.

page_text: But such a system could not produce diffusions because each step sends light in
one direction only and does not mix the rays with those emitted by the neighbouring
zones; and should the source of light be a simple point, an observer placed for
instance at A could only see one spot a, shining with a dazzling brightness. Other
systems of refracting zones have been tried in order to give some diffusion, but
have been unable to get a large angle of diffusion without loss of light. Our
system, on the contrary, enables the observer, under the same circumstances, to see
almost all the flutings shining at the same time and with a very soft intrinsic
brilliancy. Each of our flutings is a very small mixed (combined dioptrical and
catadioptrical) ring, about 5 to 10 millimeters wide, the profile of which is calculated
by the formule of optics, for distributing its own light within a very large vertical
angle, and there precisely according to the law of distribution chosen by us or
required by the circumstances.
In consequence of this method of calculating profiles all our flutings run their
rays together, as shewn in Fig. 2.; diffusion is thus obtained whereby the same law
of distribution is nearly realized by the whole of the emitted light, almost inde-
pendently of the employed source of light, so that the same envelope may be applied
to many different kinds or sources of artificial light.
We could make according to that general proceeding dioptrical flutings with
concave profiles, similar to Fig. 22; convex or concavo-convex profiles as in
Fig. 24, preserving in the three cases the same curvatures but inverting them. We
could also cut a calculated profile, such as that shewn in Fig. 22, into two or more
parts that are afterwards introverted, as in Fig. 23 in order to avoid sharp angles.
But we prefer as far more advantageous to join together in one profile two parts,
the first dioptrical (refracting) the other catadioptrical, (reflecting,) either
separated by a straight line, drawn in such a direction that no incident ray may
fall on it, as shown in Figs. 15, 16 and 17; or directly joined as shewn in
Figs. 18, 19, 20 and 21.
The rays reflected through the catadioptrical zone go out through the straight
profile in the first case or through the neighbouring dioptrical part in the second
case. The profiles of the two parts are calculated separately in the above named
manner, and when combining both together we preserve only portions that do not
send rays
in one common direction, while taking care that there remains no obscure
angle between the two groups of rays produced by the dioptrical and catadioptrical
parts.
These mixed profiles enable us to realize an angle of diffusion greater than
single profiles, and enjoy the most valuable advantage of avoiding the ordinary loss
of light as explained in a following paragraph.
Second. Internal flutings. The object of our internal flutings is to diffuse, and
sometimes to distribute the light in the horizontal direction. We calculate the
profile of the horizontal section of these flutings by a method similar to that
employed for the external rings, that is to say, we make each of the flutings diffuse
its own light within the largest possible angle of divergence, and precisely according
to the law required for the horizontal distribution. We obtain thus the important
result that the envelope or globe becomes shining over its whole surface.
In the most complicated case where the light is to be distributed unequally, each
of the flutings should have a dissymmetrical profile analogous to that of Fig. 29.
But under ordinary circumstances it is only desired to distribute the light uniformly
in the horizontal direction and all the flutings may have one similar and symmetrical
profile analogous to those of Figs. 26, 27, and 28.
We consider it desirable in that case that the shining surface may extend from
the centre to the edge of the envelope or globe, and that its apparent brilliancy
shall be nearly uniform. We obtain the first result by giving to the profile of our
flutings an obliquity at most equal to 20° from the direction of the incident rays.
The angle of incidence of about 70° thus realized is theoretically too small to allow
the rays to go out tangentially from the surface of the globe, but in practice it is
sufficient to let the shining surface seem to reach the apparent edges, and we shall

page_text: explain in the next paragraph that a greater angle of incidence would cause loss of
light. We obtain the second result by giving to our flutings a concave, convex or
concavo-convex profile so calculated that within a horizontal section such as Fig. 1
the group of rays emitted, present in each direction an intensity proportioned to
the cosine of the apparent angle of emission, that is accordingly to the same law as
the rays emitted by an incandescent black body, (known as Lembert's law). The
profiles of Figs. 26, 27, and 28 which present all three exactly the same properties
for diffusing have been calculated in that way.
We purpose retaining also the right to distribute the light horizontally according
to any other law as beforesaid, for instance to give more or less intrinsic brilliancy
in the centre than on the edges of the envelopes or globes.
Second portion. Suppression or reduction of the loss of light caused by the
employment of flutings.
All such envelopes as are made of transparent glass or crystal, may, when they
are fluted, cause a very large loss of light, which we were the first to discover by
experiment.
1st. The first and most important cause of this is the following. Every ray of
light when refracted through a horizontal dioptrical fluting, such as M, N, P,
Fig. 10, is also partially reflected into another direction b, c, which is generally too
oblique to allow the reflected light to come out of the glass when meeting again one
of its surfaces. In this way the reflected ray will be reflected many times more
before going out and get completely or partially extinguished in consequence of the
absorbing power of glass or crystal.
The proportion of light lost in this way is proportionally larger as the flutings
are more inclined upon the incident rays. It is still further increased by the effect
of the inner flutings, which give a prior deviation to the rays, thus increasing the
angle of incidence.
A triangular zone like that of Fig. 94 making an angle of incidence of 40° only in
the vertical section, reflects the rays almost totally when we add inner flutings, and
the whole of this reflected light, following the way marked by dotted lines becomes
absorbed in the glass.
We have tried different ways of more or less remedying this unknown and yet
most important defect; for example we can employ for the outer flutings concave
profiles only, disposing them in the manner shewn in Fig. 11., or preferably in
Fig. 12., (derived from Fig. 11 by simply turning over the portion p, m, g, of the
profile), in order that the reflected part of the rays may be sent back directly
towards the other side of the globe or envelope and pass out through it.
But there remains nevertheless an important loss, much of the reflected light
being too much deflected, consequently we prefer to limit the obliquity of the
dioptrical flutings to such a value that the proportion of the reflected light may
remain very small, by retaining the angle of incidence under 70° to 72° for the
inner flutings, and under 30° to 35° in vertical projection for the outer flutings.
Or, to give to the profile much obliquity (see Fig. 9) in order to obtain the total
reflection of the rays on the whole profile, p. h, and make them to go out in the
required direction through a neighbouring plane or curved profile g. h, arranged for
that purpose.
But should such catadioptrical rings be placed side by side as shewn in Fig. 9
an important part of the rays passing out of each of them, would meet the surface
of the next ones and be sent again into the glass, following a course such as that
indicated by the letters a¹, b, c, d', e¹‚ f¹, g', k', i'.
To avoid this new cause of loss, as well as to increase the vertical angle of
divergence of the group of rays emitted by each of the flutings, we have been led to
construct our special mixed profiles made of two parts, one dioptrical limited to
suitable obliquities as stated above, and the other catadioptrical, and we place the
dioptrical between the catadioptrical to give a free space to the rays going out of
the latter; moreover we suppress the sharp angles of these, which are liable to
break, by cutting a suitable portion of the dioptric part and inserting it at the

page_text: extremity of the catadioptrical profile. Thus the profiles are very thick and do not
catch dust.
We obtain another kind of mixed profiles by suppressing the straight line
between the two said parts as often as the dioptrical one may be put close by the
catadioptrical without presenting two sharp angles and in such a way that the rays
reflected by the latter part may pass out in the required direction through the
former, as shewn in Figs. 18, 19, 20, 21.
2nd. Another cause of loss arises from the reflection of the rays on the entrance
surface of the inner flutings, when these have a convex profile such as Fig. 28, for
the reflected part b. c of the light being sent on the neighbouring flutings, becomes
refracted into a direction c. d, always more oblique than the directly transmitted
rays, and can therefore be totally reflected on the outer surface of the glass,
notwithstanding the above mentioned precaution. We avoid that inconvenience by
employing concave instead of convex flutings, for as will be easily ascertained the
reflected rays are then less diverted by refraction on the near flutings, than the
directly transmitted rays. Instead of simply concave, we can employ concavo-
convex flutings with a more or less considerable convex part, as those shewn in
Figs. 26 and 27, which present greater solidity, while preserving the same
advantage.
When the flutings are grooved on the mould's surface by a grooving machine we
keep the same convex part on the whole length of each fluting varying only the
size of the concave part of the profile.
In order to make the invention easily practicable we have devised a process of
moulding, by means of moulds, glass or crystal in form of complete globes or closed
shades, with inner meridianal flutings.
In order to obtain complete globes or closed envelopes of any shape, such for
instance as spherical, ovoid and others, with interior meridianal flutings of any
profile, and with or without exterior rings or flutings of any profile which has never
yet been done, we have devised processes to form them in two parts, cut in two by
a vertical or horizontal section, and we afterwards join these parts together by
one of the known methods, glue or cement glass-soldering, metallic lattice or
otherwise.
Each of these parts is made of melted or softened glass or crystal moulded by
means of a metallic mould comprising an inner core and an outer envelope. The
flutings to be impressed on the internal surface of the globe or envelope are more or
less analogous to slices of melon and are grooved on the surface or on the core by
one of the ordinary methods such as grooving, recessing, channelling and the like.
The flutings or rings to be impressed on the outer surface of the globe are recessed
on the inner surface of the mould by means of a turning or channelling machine, or
other suitable tool.
The tools employed for this work may be either of the ordinary sort or may be
special steel tocls made on purpose, and cut exactly according to the shape of the
flutings or channellings they are intended to form.
The maker verifies the exactness of the profiles by comparison with small steel
plates or sheets cut on a reduced scale from the drawings. For the flutings of the
core that grow bigger from the poles to the equator of the globes, we use two or
more steel cu's of various sizes. We give to every inner or outer fluting the
smallest possible size, the maximum being six to ten millimeters.
When the plane of section is to be made horizontal, the envelope of the mould
has the shape shown by Fig. 4, and the core (Fig. 5) can be easily taken out of
the moulded glass. To remove the half globe we open the envelope provided with
hinges.
When the plane of section must be vertical, the envelope has the shape shown
in Figs. 6 and 7. Should the core be made of one piece only, it would be
impossible to get it out of the glass once moulded. We make accordingly the core
of many separate pieces. For instance we employ three pieces, A. B. C, shown in
vertical section in Fig. 8, and cut in such a manner that the central one A, serving

page_text: the part of a keystone between the two others, may be taken out first, the remaining
side pieces B, and C, are joined again to the platform P, which is part of the central
core A.
Third portion. Application of doubly fluted envelopes for totally reflecting the
light.
In some cases, for instance when it is required to send the whole of the light
on the ground under the envelope or globe, it is advantageous, and even necessary
to transform the upper part of it with a mirror sending the light back towards the
optical centre as shewn in Fig. 3. For that purpose the entirely reflecting prisms
used for a long time in some lighthouse apparatus are not satisfactory, for the
volume or the possible displacement of the scurce of light, is rather considerable in
comparison with the radius of the globes or envelopes, and hence it follows that a
more or less important part of the rays to be reflected does not reach the necessary
angle of incidence, and consequently escapes reflection.
Our new system of reflectors consists in combining such external rings (Fig. 13).
with internal prismatic flutings (Fig. 25) both disposed as our diffusing flutings, but
having triangular instead of curved profiles, the edge angle being 80° to 100° for
the former and 50° to 55° for the latter. Thus the incident rays already deflected
by the internal flutings undergo the total reflection on the external flutings with
absolute certainty, and moreover they are sent back, not within the plane of
incidence but in an oblique direction, that prevents them from falling again on the
source of light that would absorb them. When the place of the source of light is such
that the rays do not fall perpendicularly upon the middle surface of the envelope,
as for instance in Fig. 3, we must incline our external rings so that their bisector
remains parallel to the rays to be reflected.
We think it more advisable in some cases to alter the form of these rings by
giving them a triangular profile, with curved sides, so calculated that all the rays
falling on one of them may be sent back by the other with a suitable incidence
greater than 42° and inversely as seen in Fig. 14.
This new system of double prismatic flutings combined for total reflection, can
be employed either on some parts of our diffusing globes or envelopes, or on separate
envelopes or shades intended to serve as unalterable reflectors.
In order to make the aspect of these more agreeable we may modify the profiles
of the prisms in the following ways. 1st. By curving slightly the lines of the inner
and outer profiles, as shewn for instance in Fig. 25 by dotted lines, the result of
which would be to diffuse the reflected light and make the reflectors appear
entirely shining on their inner surface. 2nd. By adding to each of the reflecting
flutings a more or less considerable diffusing surface, as shewn for instance by dotted
lines in Fig. 13, calculated similarly to our distributing flutings, the result of
which is to produce the effect of a reflector shining on part or on the whole of its
external surface.
We will now describe the invention with reference to the accompanying drawings.
in which Figs. 1, 2, 3 and 34, represent specimens of some few selected designs of
our doubly fluted envelopes called "holophane," and Figs. 10 to 29 are similarly
selected examples of the corresponding profiles of flutings. Figs. 14 to 21 are our
special mixed profiles. Fig. 1 is a horizontal section of the envelope of Fig. 3^, or
a horizontal section drawn through the centre of the globes 2 and 3. Figs. 26, 27,
and 28 show on an enlarged scale (about five to ten times the actual size) the
profiles applicable to the internal flutings, calculated according to the law of cosines
as before stated, in order to make the globes or envelopes entirely and almost
uniformly brilliant. Profiles 26 and 27 are preferred to profile 28 on account of
the loss of light caused by the convex form.
Fig. 2 is a vertical section of a primary kind of globes intended to diffuse the
light without distributing it. The profiles being disposed in such a way that the
globes appear entirely shining when seen from below. Most of the profiles are
mixed profiles like those of the next globe Fig. 3.
Fig. 3 is a vertical section of another kind of globe for streets or other large

page_text: open spaces, intended to diffuse the light and simultaneously distribute it entirely
on the ground, according to the most suitable distribution.
Figs. 15 to 21 show on an enlarged scale the profile of the external flutings of
the globes, the portions of the surface to which each of them is applicable being
pointed out in Fig. 3. These profiles which we call mixed present the four
following advantages. They give a large angle of diffusion, avoid loss of light,
possess a good amount of solidity, and are not liable to catch dust.
Fig. 3 shows the rays issuing from the various external rings mixing themselves
together, the globe being thus made to appear brilliant almost ou its entire
height.
Fig. 3 is another example of a lantern applicable to gas or Aüer burner, or arc,
or any other light.
Figs. 22, 23 and 24 represent three profiles identical for diffusing purposes, but
having the inconvenience of causing loss of light as opposed to our mixed profiles
(Figs. 14 to 21) which avoid loss. Fig. 3 shows on the upper part of the globe
double flutings acting as a mirror.
Figs. 25 and 14 reproduce on a large scale the internal and external corresponding
profile.
Fig. 3 shows on the upper part of the lantern a separate piece acting as a
reflector. Figs. 25 and 13 are the corresponding profiles on a large scale.
Figs. 9, 9 and 10 are intended to point out how loss of light arises from partial
reflection on the external flutings when the angle of incidence exceeds 34° to 35°;
and Fig. 28 to show how other losses arise from partial reflection on the surface of
the inner flutings when their profile is made convex only.
Fig. 29 shows an example of dissymmetrical inner flutings intended to distribute
light unevenly in the horizontal direction while effecting perfect diffusion.
Fig. 30 points out the ancient method of steps employed for making on the
outer surface of a lantern globe for distributing but not diffusing steps, as opposed
to our system of simultaneously distributing and diffusing flutings shown in Fig. 3.
Figs. 4 and 5 show the system of moulding by pressure devised for making
doubly fluted globes in two pieces cut horizontally, Fig. 4 being a vertical section
of the envelope provided with hinges, and Fig. 5 a vertical elevation of the fluted
core.
Figs. 6, 7 and 8 show a second system of moulding by pressure devised for
making the same globes in two halves cut vertically. Figs. 6 and 7 being the
horizontal plane and vertical section of the envelope, and Fig. 8 the vertical section
of the core.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that we
claim is
1. The manufacture on every kind of globes, envelopes, shades or lantern glasses
of transparent, colorless or colored glass, or crystal, of small external parallel
flutings in form of mixed rings, i.e. rings consisting practically of two profiles the
ope refracting (dioptrical,) the other reflecting before refracting (catadioptrical,)
these two profiles being assembled or intermingled together with or without the
help of a neutral part, each of them being calculated for distributing its own
light within the largest possible vertical angle and there as much as possible
according to the law of distribution required for the whole of the light, in order
to obtain diffusion combined with the most suitable distribution in each special
case, as herein described and set forth.
2. The combination on the same globes, envelopes, shades or lantern glasses of
the said horizontal flutings with internal vertical flutings, offering to the incident
rays an angle of incidence of at least 70° when the source of light is of small
size, and a lesser angle when the source of light is large, in order that the globe
may appear "holophane" that is to say brilliant on nearly the whole of its
apparent surface; the profile of these flutings being calculated to realize in the

page_text: horizontal direction the law of distribution specially required in each case and when
diffusion only is needed, the law of the cosine of the angle of emission in order to
render uniform the apparent intrinsic brilliancy, as herein described and set
forth.
3. The suppression or reduction of the loss of light caused by the use of external
flutings by taking off from the dioptrical or catadioptrical profiles every part that
could reflect the rays totally or even partially (while taking account of the prior
deviation due to internal flutings) into directions that cause them to remain in
the glass or crystal instead of passing directly outward, and by inserting dioptrical
parts between every two catadioptrical rings, in order that the rays may pass out
freely through the straight or curved surfaces disposed for that purpose without
encountering any other fluting, as herein described and set forth.
4. The suppression or reduction of the loss of light caused by the use of internal
flutings and by making their profiles concave or concavo-convex, instead of simply
convex, and by reducing to 70° at most, their maximum angle of incidence, in
order to reduce the resulting angle of incidence on the external surface as herein
described and set forth.
5. The method of forming parts of the globes or envelopes as separate envelopes,
reflecting the rays entirely, and sending them back as a mirror, although the source
of the light may be of large size or be displaced from its proper position; by means
of combined triangular inner and outer flutings, the former being made to impart
to the rays a supplementary deviation; and to make the sides of the profiles
either plane or curved according to the circumstances, as herein described and set
forth.
6. The combination of the total reflection thus obtained with a supplementary
effect of diffusion, in order to let the reflector shine on its whole internal surface by
curving slightly the faces of the prismatic flutings and allowing it to shine on its
outer surface by adding to each reflecting inner and outer fluting portions more or
less important of our diffusing flutings described in Claims 1 and 2, as herein
described and set forth.
Dated this 12th day of July 1804
S. S. BROMHEAD,
97 Newgate Street, London, E.C., Patent Agent.