CERTAIN IMPROVEMENTS IN ARTIFICIAL LIGHT
Year: 1846

page_text: TO ALL TO WHOM THESE. PRESENTS SHALL COME, I, RICHARD
CLARKE BURLEIGH, of the City of Bath, in the County of Somerset, Gentleman,
send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Royal Letters Patent under the Great Seal of Great Britain, bearing date at
Westminster, the Twenty-eighth day of August, in the tenth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
Richard Clarke Burligh, Her especial licence, full power, sole privilege and
authority, that I, the said Richard Clarke Burleigh, my executors, admi-
nistrators, and assigns, and such others as I, the said Richard Clark Burleigh,
my executors, administrators, or assigns, should at any time agree with, and
no others, from time to time and at all times during the term of years therein
mentioned, should and lawfully might make, use, exercise, and vend, within Eng-
land, Wales, and the Town of Berwick-upon-Tweed, my Invention of "CERTAIN
IMPROVEMENTS IN ARTIFICIAL LIGHT;" in which said Letters Patent is contained
proviso, obliging me, the said Richard Clarke Burleigh, by an instrument
in writing under my hand and seal, particularly to describe and ascertain the
nature of my said Invention, and in what manner the same is to be performed,
and to cause the same to be inrolled in Her Majesty's High Court of Chancery
within six calendar months next and immediately after the date of the said
in part recited Letters Patent, as in and by the same, reference being there-
unto had, will more fully and at largè appear.

page_text: NOW KNOW YE, that in compliance with the said proviso, I, the said
Richard Clarke Burleigh, do hereby declare that the nature of my said Inven-
tion, and the manner in which the same is to be performed, is particularly
described and ascertained in and by the following description thereof (that is
to say):-
In order that the nature of the improvements forming the subject of the
present Invention may be rendered evident and intelligible, a few preliminary
remarks on the nature and properties of solar and artificial light are necessary.
In solar light three colors or-rays are so combined as to yield in transmission
through the azure-colored medium of the atmosphere a perfect or colorless
light, (that is to say,) those luminous rays which emanate by radiation from
the sun, and reach the earth, consist of three primitive colors,, red, yellow, and
blue, combined in proportions that form a compound ray having no predomi-
nating tint, in other words, perfectly colorless. Solar light therefore, or the
luminous rays emanating from the sun, being by composition the purest and
most perfect of any with which we are acquainted, I adopt such light as the
standard of comparison to which every other kind of light is to be referred in
judging of its quality and effects. Now, the difference between the illuminative
effects and qualities of solar or natural light, and of that produced by artifical
means, will be found to consist principally in this; viz., that in the artificial
spectrum, the red and yellow portions or rays greatly predominate over the
blue, (that is to say,) the former are present or emanate from the source of
artificial light in quantities over and above such as are required for a just and
harmonious combination with the blue rays to produce a perfectly colorless
light similar to solar light. This excess of red and yellow rays may not only
be proved by the prism, but as they appear to emanate (quoad their excess) in
a free or uncombined state, they can be recognized as a positive tint or color
overlaying or painting, as it were, all objects on which they fall; hence arises
the difficulty or inability of ascertaining with precision delicate shades of color
by artificial light, and the excess of these red and yellow rays also causes pain
and fatigue to the eye when long exposed to its influence. This vitiating and
injurious excess of color existing in the artificial spectrum can be corrected in
any desired degree in a perfectly simple and infallible manner. The correction
is effected by transmitting the rays of artificial light through glass, so prepared
as to present, when formed in a proper manner, a medium analagous to that
presented by the azure tint of the atmosphere to solar or natural light. It
cannot be doubted, that to the purifying medium of the azure atmosphere,
solar light was, in great measure, its extreme whitness and delicacy; and by

page_text: the use of such prepared glass, to which I have (looking to its effects in use)
given the name of achromatic glass, the following important improvements are
gained: The quality of artificial light becomes greatly improvedl as to purity,
being more or less deprived at pleasure of its excess of color, and consequently
of its offensive and painful glare; its powers of diffusion, and the ability to
ascertain by its delicate shades of color correctly, are greatly increased; the
shadows thrown by the objects exposed to its rays are transparent, gray, and
cool, thus altogether different from the hot and brown opacities forming the
shadows of incorrected light; and, lastly, the points most highly illuminated by
the corrected light are brilliant, pure, and of true tone, in place of being loaded
with a glaring and unnatural ruddiness.
Of the quality and source of the achromatic power. It is a law of light
that when luminous rays are transmitted through a colored medium, a certain
proportion of the rays, complimentary to the color of the medium presented,
shall be neutralized, or so disposed of as not to be in active and visible agency
as portions of the light transmitted. Thus, if light be made to pass through
ruby tinted glass, it will appear ruddy, because the ruby tint, neutralizing the
colors complimentary to its own hue, namely, the yellow and the blue; allows
the red to predominate in radiation; yellow tinted glass will also neutralize
the blue and the red ray; and blue tinted glass, "the yellow and the red.
From this it will be evident that, inasmuch as the excess of color to be
corrected in artificial light exists in the red and yellow portions of the artificial
spectrum, the base of the material or compound possessing such power of
correction must always be such as shall impart to glass a blue tint or tinge
of color, and such tint or color will, within certain limits, always be a warranty
and assurance that the glass so tinted possesses achromatic or purifying pro-
perties with regard to artificial light. The material now in general use for the
purpose of imparting a blue color to all vitrifiable substances, namely, cobalt,
in those states of preparation known as "smalt," or "azure blue," and ""zaffre,"
imparts to glass the power of achromatizing artificial light with certainty. The
lightest appreciable tint that can be given to glass by these preparations of cobalt,
(that is to say; a tint or tinge but just or barely visible to the eye: when. the
glass is in the form adapted to use,) renders such glass achromatic, or a purifyer
of artificial light, by..imparting to it the power of correcting some certain por-
tions of the degree of color existing in its spectrum; and. from this the lightest
appreciable tint or tinge of color, which I call the lowest achromatic power, a
succession of powers may be obtained by a gradual increase in the proportion
of the achromatizing material added, and consequently in the depth of tint,

page_text: until that point or power be reached which forms the natural boundary of their
range, (that is to say,) a point or power where or by which all excess of red or
yellow color in the emanating rays is neutralized. It is manifest that the
range between the lowest and the highest achromatic powers is capable of
numerous divisions into progressive degrees or intensities, each of which will
'be found to possess some peculiar quality or property in use that renders it
most desirable in accordance with the required effects of illumination, such
effects commencing at the lowest and ending at the highest attainable point or
*degree of improvement. Thus, the exact tint or power sought in any particular
instance will depend on the judgment of the manufacturer, guided by the
considerations of the nature of the medium required as to form and thickness,
and the character and quality of the light previous to correction, while the
exact quantity of achromatizing material added to obtain the required result
will depend on its purity and strength as a coloring agent, and also upon the
peculiar character of artificial light to be corrected or achromatized. I adopt
the following tests to determine the point of highest achromatic power :-Let
a direct ray of the corrected artificial light to be tested (the light being
enclosed in a fitting box or lantern), fall on a white substance, as paper, side by
side with a direct ray of a warm sun-light (as of a summer noon), in a room
to which no other ray of light has access; so long as the ray of corrected
artificial light is of a warmer or ruddier quality than the ray of solar light,
the achromatic power is short of its highest intensity, and therefore within the
range of true achromatic powers, or further and more perfect correction. If
the artificial light appear colder or bluer, the medium is too deeply tinged, and
is not an achromatic but a colored medium, applicable in no way to the true
improvement of artificial light by the correction of the excess of colored rays
emanating therefrom. If the qualities of the respective rays be the same, then
it will be evident that the highest point has been reached, and the medium is
at its highest available power or state. I sometimes adopt other tests to
ascertain whether the corrected artificial ray has been properly achromatized.
I do not, however, think it necessary to give a detailed explanation of all the
different means that may be employed, as the above has been found both
simple and effective.
It may here be observed, that the highest possible attainable correction of
the artificial spectrum fails to produce a light in all respects identical with sun-
light; a point may, indeed, be reached beyond which the corrected light ceases
to improve in purity as compared with the ray of sun-light; but the essential
difference in the two sources of light, as to intensity of combustion, powers of

page_text: radiation and penetration, of refrangibility, distance of source, and nature of the
respected media interposed, must prevent the attainment in corrected artificial
light of many qualities which exist in the luminous rays emanating from the
sun; but that there is a visible and positive improvement in the quality of the
artificial spectrum by transmitting the artificial rays through the achromatic or
purifying medium presented under the form of achromatic argand chimney or
glass is evident, and that such improvement is caused by means analagous to
those which render solar light so perfect, can be demonstrated by practical
experiment. The achromatizing material, though necessarily producing a bluish.
tinge in the glass containing it, as evidence of its presence, cannot be considered
a coloring agent merely, but is an essential constituent of achromatic glass,.
a constituent on the presence of which in proper proportions absolutely and
entirely depends the existence of those qualities which render the glass,
achromatic, and permit its successful application to artificial light. With the
exception of the achromatizing material, the ingredients of achromatic glass in
no respect differ from those of glass employed in the manufacture of articles,.
such as chimnies, globes, bulbs, shades, or other shapes which are usually.
employed to protect artificial light from the influence of currents or draughts
of air, or other disturbing causes, or to produce the proper current of air
that may be necessary to maintain perfect combustion.
My Invention does not, therefore, relate to improvements in the process
of manufacturing glass, nor to the ingredients employed in such manu-
facture, and I do not intend to confine myself to the employment of any
particular substance or substances, such as cobalt, azure blue, or zaffre, by.
mixing which with the other ingredients of glass during the manufacture,
a blue tint, of any required depth of color, may be imparted to the glass,
by employing suitable proportions or quantities; nor do I intend to confine
myself to any particular proportions or quantities in which the achro-
matizing ingredient or ingredients is or are to be mixed with the other
ingredients, as such proportions must depend upon the quality of the artificial
light to be corrected, and the nature of the materials of which the glass is to
be composed, and can only be arrived at by actual experiment to suit the
several cases. The degree of intensity of color which will be required to
correct the colored rays of artificial light having been ascertained in the manner
herein described, the manufacturer will be at no loss to impart the proper tint
to the glass, by the admixture of a suitable quantity of the achromatizing
ingredient. The molten metal having been properly prepared, glasses of
various shapes and forms may be made by the workman, to suit different kinds.

page_text: of burners, such as plain, straight, or other shaped chimnies, bulbs, globes,
shades, or glasses of various kinds, as circumstances or cases may render
desirable or necessary, or taste may direct; or, in place of mixing the achro-
matizing material with the ingredients of which the glass is composed, so as to
cause thein to enter into and pervade the mixture of vitrified matters, I some-
țimes 'case uncolored glass with blue or colored glass of a proper tint, or I
paint or stain the surface of uncolored glasses made in the ordinary manner,
taking care to impart the proper tint for correcting the colored rays. This
operation is performed in precisely the ordinary manner, and with the materials
usually employed for painting or staining glass. The colored rays of artificial
light may also be, to a great extent, corrected by reflection, by employing
shades or reflectors made of porcelain or semi-transparent glass, the reflecting
surfaces of which should be stained, painted, or colored blue of the
proper tint.
Having now described the nature and object of my Invention, and the
manner of carrying the same into effect, I wish it to be understood that I am
aware that glasses have been heretofore stained of various colors, and have been
employed for the purpose of ornament, or for imparting various hues or colors
to objects which have been illuminated by light passing through them. I do
not, therefore, wish to claim the broad principle of employing variously colored
glasses; but that which I consider to be new, and therefore wish to secure to
myself under the herein-before in part recited Letters Patent, is, the improve-
ment of artificial light by the application or employment of glass composed of
the substance or substances usually employed, or any other analagous ones
suitable for this manufacture, with the addition of a material which, when in
union with the vitrifiable matter or glass, or painted on, laid over, or made to
cover the same, shall produce or impart a shade or tinge of a blue color of a
varying depth, according to the ratios or proportions in which the said colouring
material is added to, painted on, laid over, or made to cover the other usual and
well-known.ingredients necessary to the formation of glass; and by the employ-
ment of which coloring matter I am enabled to achromatize, purify, or correct
the rays of artificial light, by causing them to pass through glass so tinted or
colored, in the manner and within the limits above detailed. I also claim the
use of colored shades or reflectors, as above set forth, in which the reflecting
surfaces are colored, tinted, stained, painted, or covered with some achroma-
tizing material, for the purpose of correcting the colored rays of artificial light.
I claim the application of such achromatic glass or reflector, in combination
or union with any form or shape that may be employed for the purposes above
mentioned, or which may be suitable for shading, or protecting, or reflecting

page_text: artificial light from currents or draughts of air, or for other purposes, such as
producing and guiding such artificial currents of air to the flames, as may be
found necessary to produce a perfect combustion of the matter yielding such
light.
In witness whereof, I, the said Richard Clarke Burleigh, have hereunto
set my hand and seal, this 18th day of February, in the year of our
Lord One thousand eight hundred and forty-seven.
RICHARD CLARKE (L.s.) BURLEIGH.
AND BE IT REMEMBERED, that on the same Eighteenth day of
February, in the year above mentioned, the aforesaid Richard Clarke Burleigh
came before our Lady the Queen in Her Chancery, and acknowledged the
Specification aforesaid, and all and every thing therein contained, in form above
written. And also the Specification aforesaid was stamped according to the
tenor of the Statute in that case made and provided.
Inrolled the Twenty-seventh day of February, in the year above written. .

page_text: In the Matter of a Patent granted to Richard Clarke Burleigh, late
of the City of Bath, but now of Featherstone Buildings, Holborn, in
the County of Middlesex, Gentleman, for his Invention of "CERTAIN
IMPROVEMENTS IN ARTIFICIAL LIGHT," bearing date at Westminster,
the Twenty-eighth day of August, One thousand eight hundred and
forty-six.
DISCLAIMER AND MEMORANDUM OF ALTERATION entered by the
said Richard Clarke Burleigh with the Clerk of the Patents of England,
pursuant to an Act passed the fifth and sixth years of His late Majesty's
reign, intituled "An Act to amend the Law touching Letters Patent for
Inventions."
I, the said Richard Clarke Burleigh, do hereby declare that in compliance
with the proviso contained in, the said Letters Patent, I enrolled on or before
the Twenty-seventh day of February, One thousand eight hundred and forty-
seven, in the Petty Bag Office of the High Court of Chancery, a Specification
of my said Invention.
And I do hereby further declare that since the enrolment of the said Speci-
fication I have discovered in a printed book certain suggestions for purifying
light by means of tinted shades similar to those proposed by me, and that from
this cause, and from my belief, after various experiments, that the purification
of light by such means cannot, with any degree of certainty, be effected, I am
desirous of disclaiming such parts of my Specification as describe my Invention
to consist in purifying artificial light by means of tinted or painted shades,
for the purpose of making my said Invention of more general benefit and
advantage.
And for the reasons aforesaid, I, the said Richard Clarke Burleigh, do hereby
disclaim and omit such parts of my said Specification as relate to purifying
artificial light by means of tinted or painted shades; and after making such
disclaimer or omission, I add such words as are necessary to make my said
Specification more intelligible, and which said Specification will then be in the
words following, that is to say-
"In order that the nature of the improvements forming the subject of
"the present Invention may be rendered evident and intelligible, a few pre-
liminary remarks on the nature and properties of solar and artificial light are
66 necessary.
$6

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"
In solar light, three colors or rays are so combined as to yield in trans-
"mission through the azure-coloured medium of the atmosphere a perfect or
colorless light, (that is to say,) those luminous rays which emanate by
"radiation from the sun, and reach the earth, consist of three primitive
colors, red, yellow, and blue, combined in proportions that form a com-
"pound ray having no predominating tint, in other words, perfectly colorless.
"Solar light therefore, or the luminous rays emanating from the sun, being
by composition the purest and most perfect of any with which we are ac-
"quainted, I adopt such light as the standard of comparison to which every
"other kind of light is to be referred in judging of its quality and effects.
"Now, the difference between the illuminative effects and qualities of solar
or natural light, and of that produced by artificial means, will be found to
"consist principally in this, (viz), that in the artificial spectrum the red and
yellow portions of the rays greatly predominate over the blue, (that is to
"say,) the former are present or emanate from the source of artificial light in
quantities over and above such as are required for a just and harmonious
"combination with the blue rays to produce a perfectly colorless light, similar
"to solar light. This excess of red and yellow rays may not only be proved by
"the prism, but as they appear to emanate (quoad their excess) in a free or
"uncombined state, they can be recognized as a positive tint or color, overlaying.
or painting, as it were, all objects on which they fall; hence arises the diffi-
"culty or inability of ascertaining with precision delicate shades of color by
"artificial light, and the excess of these red and yellow rays also causes pain
"and fatigue to the eye when long exposed to its influence. This vitiating.
"and injurious excess of color existing in the artificial spectrum can be cor-
"rected in any desired degree in a perfectly simple and infallible manner.
"The correction is effected by transmitting the rays of artificial light
through glass, so prepared as to present, when formed in a proper manner, a
"medium analogous to that presented by the azure tint of the atmosphere to
"solar or natural light. It cannot be doubted, that to the purifying medium
"of the azure atmosphere, solar light owes, in great measure, its extreme
"whiteness and delicacy, and by the use of such prepared glass, to which
"I have (looking to its effect in use) given the name of "achromatic glass,"
"the following important improvements are gained:-The quality of artificial
light becomes greatly improved as to purity, being more or less deprived
(at pleasure) of its excess of color, and consequently of its offensive and
painful glare; its powers of diffusion, and the ability to ascertain by it
"delicate shades of color correctly, are greatly increased; the shadows thrown
by the objects exposed to its rays are transparent, grey, and cool, thus
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page_text: altogether different from the hot and brown opacities forming the shadows
"of incorrected light; and, lastly, the points most highly illuminated by the
"corrected light are brilliant, pure, and of true tone, in place of being loaded
"with a glaring and unnatural ruddiness."
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"Of the quality and source of the achromatic power.-It is a law of light
"that when luminous rays are transmitted through a colored medium a
" certain proportion of the rays, complimentary to the color of the medium
"presented, shall be neutralized or so disposed of as not to be in active and
"visible agency as portions of the light transmitted. Thus, if light be made to
pass through ruby tinted glass, it will appear ruddy, because the ruby tint,
neutralizing the colors complementary to its own hue, namely, the yellow and
"the blue, allows the red to predominate in radiation; yellow tinted glass will
"also neutralize the blue and the red ray; and blue tinted glass, the yellow and
"the red. From this it will be evident that inasmuch as the excess of color
"to be corrected in artificial light exists in the red and yellow portions of the
"artificial spectrum, the base of the material or compound possessing such
power of correction must always be such as shall impart to glass a blue tint
or tinge of color, and such tint or color will, within certain limits, always be
a warrantry and assurance that the glass so tinted possesses achromatic or
purifying propertics with regard to artificial light.
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66
"The material now in general:use for the purpose of imparting a blue color
"to all vitrifiable substances, namely, cobalt, in those states of preparation
"known as "smalt," or "azure blue," and "zaffre," imparts to glass the
< power of achromatizing artificial light with certainty.
"The lightest appreciable tint that can be given to glass by these prepa-
"rations of cobalt, (that is to say,) a tint or tinge but just or barely visible to
"the eye when the glass is in the form adapted to use; renders such glass
"achromatic or a purifier of artificial light, by imparting to it the power of
66
correcting some certain portions of the degree of color existing in its spec-
"trum; and from this, the lightest appreciable tint or tinge of color (which I
"call the lowest achromatic power), a succession of powers may be obtained
by a gradual increase in the proportion of the achromatizing material added,
"and consequently in the depth of tint, until that point or power be reached
"which forms the natural boundary of their range, (that is to say,) a point or
power where or by which all excess of red or yellow color in the emanating
rays is neutralized. It is manifest that the range between the lowest and
the highest achromatic powers is capable of numerous divisions into pro-
gressive degrees or intensities, each of which will be found to possess some.
peculiar quality or property in use that renders it most desirable in accordance
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"with the required effects of illumination, such effects commencing at the
lowest and ending at the highest attainable point or degree of improvement.
"Thus the exact tint or power sought in any particular instance will depend
"on the judgment of the manufacturer, guided by the considerations of the
"nature of the medium required as to form and thickness, and the character
"and quality of the light previous to correction, while the exact quantity of
achromatizing material added to obtain the required result will depend on
its purity and strength as a coloring agent, and also upon the peculiar
"character of artificial light to be corrected or achromatized. I adopt the
following tests to determine the point of highest achromatic power:-
"Let a direct ray of the corrected artificial light to be tested (the light
"being enclosed in a fitting box or lantern, fall on a white substance, as
paper, side by side with a direct ray of a warm sun-light (as of a summer
"noon) in a room to which no other ray of light has access.
So long
as the ray of corrected artificial light is of a warmer or ruddier quality
than the ray of solar light, the achromatic power is short of its highest
intensity, and therefore within the range of true achromatic powers, or
"further and more perfect correction. If the artificial light appear colder
"or bluer, the medium is too deeply tinged, and is not an achromatic, but a
"colored medium, applicable in no way to the true improvement of artificial
light by the correction of the excess of colored rays emanating therefrom.
"If the qualities of the respective rays be the same, then it will be evident
that the highest point has been reached, and the medium is at its highest
"available power or state. I sometimes adopt other tests to ascertain
"whether the corrected artificial ray has been properly achromatized.
66
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6
I
do not, however, think it necessary to give a detailed explanation of all
"the different means that may be employed, as the above has been found
"both simple and effective.
66
"It may here be observed, that the highest possible attainable correction
"of the artificial spectrum fails to produce a light in all respects identical
"with sun-light. A point may indeed be reached beyond which the corrected
light ceases to improve in purity as compared with a ray of sun-light, but
"the essential difference in the two sources of light, as to intensity, of com-
bustion, powers of radiation and penetration, of refrangibility, distance of
"source, and nature of the respective media interposed, must prevent the
" attainment in corrected artificial light of many qualities which exist in the
"luminous rays emanating from the sun; but that there is a visible and
positive improvement in the quality of the artifical spectrun by transmitting
the artificial rays through the achromatic or purifying medium presented
66
66

page_text: "under the form of achromatic argand chimney or glass is evident, and that
"such improvement is caused by means analogous to those which render solar
light so perfect can be demonstrated by practical experiment.
"
66
"The achromatizing material, though necessarily producing a bluish tinge
"in the glass containing it, as evidence of its presence, cannot be considered a
coloring agent merely, but is an essential constituent of achromatic glass, a
"constituent on the presence of which, in proper proportions, absolutely and
entirely depends the existence of those qualities which render the glass
achromatic, and permit its successful application to artificial light. With
"the exception of the achromatizing material, the ingredients of achromatic
glass in no respect differ from those of glass employed in the manufacture
" of articles such as chimneys, globes, bulbs, shades, or other shapes, which are
" usually employed to protect artificial light from the influence of currents
66
26
or draughts of air, or other disturbing causes, or to produce the proper
"currents of air that may be necessary to maintain perfect combustion.
66
My Invention does not, therefore, relate to improvements in the process of
"manufacturing glass, nor to the ingredients employed in such manufacture,
" and I do not intend to confine myself to the employment of any particular
".substance or substances, such as cobalt, azure blue, or zaffre, by mixing which
" with the other ingredients of glass during the manufacture a blue tint of any
required depth of color may be imparted to the glass, by employing suitable
proportions or quantities; nor do I intend to confine myself to any particular
"proportions or quantities in which the achromatizing ingredient or ingre-
"dients is or are to be mixed with the other ingredients, as such proportions
"must depend upon the quality of the artificial light to be corrected, and the
"nature of the materials of which the glass is to be composed, and can only
"be arrived at by actual experiment to suit the several cases. The degree of
intensity of color which will be required to correct the colored rays of
"artificial light having been ascertained in the manner herein described, the
*** manufacturer will be at no loss to impart the proper tint to the glass by the
"* admixture of a suitable quantity of the achromatizing ingredient. The
"molten metal having been properly prepared, glasses of various shapes and
"forms may be made by the workman, to suit different kinds of burners, such
"as plain, straight, or other shaped chimneys, bulbs, globes, shades, or glasses
"" of various kinds, as circumstances or cases may render desirable or necessary,
"or taste may direct."
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65
Having now described the nature and object of my Invention, and the
"manner of carrying the same into effect, I wish it to be understood that I am
"
aware that glasses have been heretofore stained of various colors, and have

page_text: "been employed for the purpose of ornament, or for imparting various hues
"or colors to objects which have been illuminated by light passing through
"them; I do not, therefore, wish to claim the broad principle of employing
variously colored glasses; but that which I consider to be new, and therefore
"wish to secure to myself under the herein-before in part recited Letters
"Patent, is, the improvement of artificial light by the application of achro-
"matic glass (made as above described) as a medium for transmitting
"artificial light, such glass being of any form or shape that may be employed
"for shading or protecting artificial light from currents or draughts of air, or
"for producing and guiding such artificial currents of air to the flames as
may be found necessary to produce a perfect combustion of the matter
"yielding such light."
In witness whereof I, the said Richard Clarke Burleigh, have hereunto
set my hand and seal, this Twenty-sixth day of May, One thousand
eight hundred and forty-eight.
This to certify, that Richard Clarke Burleigh, late of the City of Bath, but
now of Featherstone Buildings, Holborn, in the County of Middlesex, Gentle-
man, had applied to me for leave to file with you the above-written Disclaimer
and Memorandum of Alteration of a certain Invention, for which Letters
Patent were granted to him under the Great Seal, 28th August 1846, and
of the Specification enrolled 27th February 1847; and on considering the
said application, I directed him to advertize his said Disclaimer and Memo-
randum of Alteration in the London Gazette, and in the Times and Daily News
newspapers; and such advertizements have been duly made in the said London
Gazette, and in the Times and Daily News newspapers, and no objection
having been made to the said application, I have accordingly granted leave to
the said Richard Clarke Burleigh to file his said Disclaimer and Memorandum

page_text: of Alteration, pursuant to the Statute passed in the 5th and 6th. years of His
late Majesty, entitled An Act to amend the Law touching Letters Patent for
Inventions..
JOHN JERVIS,
Entered with and filed by the Clerk of
the Patents for England, this 30th day of
May 1848.
Temple, 29th May 1848.
Inrolled the Thirtieth day of May, in the year above written.