IMPROVE- MENTS IN OPTICAL & ILLUMINATING APPARATUS
Year: 1861

page_text: LETTERS PATENT to William Clark, of 53, Chancery Lane, in the County
of Middlesex, Engineer and Patent Agent, for the Invention of "IMPROVE-
MENTS IN OPTICAL & ILLUMINATING APPARATUS."-A communication
from abroad by William Ferdinand Count de Douhet, of 29, Boule-
vart St. Martin, Paris, in the Empire of France.
Sealed the 4th February 1862, and dated the 21st August 1861.
PROVISIONAL SPECIFICATION left by the said William Clark at the
Office of the Commissioners of Patents, with his Petition, on the 21st
August 1861.
I, WILLIAM CLARK, of 53, Chancery Lane, in the County of Middlesex,
Engineer & Patent Agent, do hereby declare the nature of the said Inven-
tion for "IMPROVEMENTS IN OPTICAL & ILLUMINATING APPARATUS," to be as
follows:-
This Invention relates to improvements in optical instruments, reflectors,
& illuminating apparatus. In optical instruments I construct all kinds of
lenses of two or more pieces or plates of glass, either blown or cast. I connect
these pieces together at the edges so as to leave spaces between, which I fill
with water, chloroform, sulphuret of carbon, or other liquid or solution of any
colors suitable for the purposes of augmenting the refracting power of the
lenses.

page_text: I also form partitions, reflectors, or illuminating apparatus for binnacles or
other purposes of glass, mica, or other translucent substances, which are made
hollow, and with or without divisions, and filled with one or various refracting
liquids, either colored or uncolored, for the purpose of allowing the light to
penetrate, and thereby produce luminous effects.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Clark in the Great Seal Patent Office on the
19th February 1862.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
CLARK, of 53, Chancery Lane, in the County of Middlesex, Engineer &
Patent Agent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-first day of August, in the year of our Lord
One thousand eight hundred and sixty-one, in the twenty-fifth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said William Clark, Her special licence that I, the said William Clark,
my executors, administrators, and assigns, or such others as 1, the said William
Clark, 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 OPTICAL
AND ILLUMINATING APPARATUS," a communication to him from abroad by
William Ferdinand Count de Douhet, of 29, Boulevart St. Martin, Paris, in
the Empire of France, upon the condition (amongst others) that I, the said
William Clark, 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 Office within six calendar months next and immediately after the date
of the said Letters Patent.
NOW KNOW YE, that I, the said William Clark, do hereby declare
the nature of the said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the fol-
lowing statement (that is to say):-
The electric light will always form an imperfect substitute for gas so long

page_text: as the problem of the divisibility of its spark remains unsolved, nevertheless
regulators now in use afford an equable light of an almost constant character,
and even now might be used with advantage in public squares, streets, and
otherwise, were it not for two great objections which still attend it, viz.,
1st, that of producing a dazzling effect, and being also of so small a volume as
to appear to contract itself instead of expanding in the atmosphere; 2ndly,
that of distorting objects illuminated by it and giving them an unnatural
appearance, which is unpleasant, and ultimately becomes intolerable to
the eye.
i
In order to obviate or at least diminish this double defect I employ the
improved apparatus herein described, which will also apply to various
other optical instruments. For this purpose I employ the crystal or flint
glass ordinarily used in similar cases, but as this substance is impracticable,
especially if bent surfaces of large dimensions are required, forming a kind of
continuously diverging meniscus round the luminous point. Experiments
have thus led me to employ blown glass as a substitute for the solid glass, or
in ordinary cases white glass, both of a less weight, and which by their
flexibility when heated are susceptible of taking any form. Thus the object
to be attained consists of producing in crystal or blown glass of a single piece,
or by preference of glass bent of different forms, and simply superposed,
either on convex, concave, or on plane surfaces, but always hermetically joined
together, representing the normal or derivative figures of all the ordinary
optical apparatus & instruments, so as to obtain at will either mirrors,' convex
or concave lenses, object prisms, and all other similar objects of all dimensions.
These objects thus obtained will be hollow or empty, & in order to give them
a beiter refractory power for producing the desired result I fill the hollow
space with .limpid water, adding, in winter, a quantity of alcohol necessary to
prevent the freezing if employed for outdoor illuminating purposes, and add
sulphuret of carbon, chloroform, and other liquid possessing greater power of
refraction than water. If they are required for the observation of stars &
scientific purposes, although water is suflicient in most cases, the chief
advantage of this kind of apparatus consisting in the possibility of obtaining
them at a less price and of large dimensions, which permits of interposing
layers of water of a sufficient extent.
The application of these principles may be greatly varied, but to mention
those only which are useful for lighting purposes, I would observe that an
ordinary lantern divided into chambers by means of circular concentric glasses
diverging the one from the other towards the upper part will disperse light in
all directions when the chambers are filled with water, especially if it is

page_text: furnished with a good reflector at top. The same lantern may have the form
of a polyhedron, with flat multiplied faces enclosed in an envelope consisting
entirely of glass, when the lighting effect will be very remarkable. In this
case the reflector of the cap should be composed of as many polished surfaces
as there are in the polyhedron, so that they will be constantly opposed the one
to the other. This improved lighthouse lantern may be applied to all lighting
purposes, and be constructed as required, either of glass or crystal blown of
the desired form of large or small dimensions. When lighted by a number of
gas jets its effect is very striking, and with the electric light burning in the
interior the effect becomes dazzling; while if the liquid in the interior is
colored of an orange tint, for example, the colored light resembles that of day,
and is no longer objectionable to the eye. It has been before mentioned that
the glass or crystal partitions which form the exterior of the lanterns may be
varied in form, as it is not the special form of the lantern which I claim, but
simply the principle of constructing them with partitions filled with refracting
liquids, which may be of any tint desired. All liquids in general may be
applied to the decoration. and when illuminating apparatus of this kind is to
be applied to the decoration of theatres or public entertainments the richness
and novelty of the shades or tints which radiate in a magnified form from the
lenticular apparatus produces a very effective display.
Thus the chief features of this Invention are,-
First, the application of apparatus furnished with compartments of crystal
or glass composed of one or more hollow pieces as substitutes for like or
different forms to those in present use for optical purposes, whereby to repro-
duce in all scales of magnitude of scientific or other experiments, by means
of liquids contained in the spaces between the glass, for the purpose of pro-
ducing the necessary refracting power.
Secondly, the construction of lanterns with partitions of crystal or hollow
glass filled with liquids, either colored or limpid, as herein described, for the
purpose of increasing the dispersive power of the candle, oil, gas, or electric
I also
light according to the nature of the illuminating agent employed.
claim all illuminating glasses, lanterns, or globular forms suitable as substi-
tutes for the plain or solid forms ordinarily used, having hollow partitions,
above described, for the introduction of white or colored liquids for the pro-
duction of infinitely varied and novel effects by regulating the shades of the
liquids and the containing sides.
Thirdly, I will add that by the word crystal I include flint and all other
glass, and also that material employed in optical experiments, the Invention
consisting of the application of all transparent matters, either colored or

page_text: uncolored, and polished or unpolished, having hollow spaces or compartments
filled with liquids instead of the ordinary solid glass hitherto employed for
general illuminating purposes, as also for the production of effects of white or
colored fire at public entertainments.
In witness whereof, I, the said William Clark, have hereunto set my
hand and seal, this Eighteenth day of February, in the year of our
Lord One thousand cight hundred and sixty-two.
Witness,
W. G. E. SWINNOCK,
53, Chancery Lane,
London.
W. CLARK. (L.S.)