AN IMPROVE- MENT IN TELESCOPES
Year: 1810

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, Joseph
MANTON, of Davies Street, Berkeley Square, in the County of Middlesex,
Gun Maker, send greeting.
WHEREAS His present Majesty King George the Third, in and by His
Letters Patent under the Great Seal of Great Britain, bearing date at
Westminster, the Twenty-third day of January last, for Himself, His heirs
and successors, did give and grant unto me, the said Joseph Manton, His
special licence, full power, sole privilege and authority, that I, the said
Joseph Manton, my executors, administrators, and assigns, and every of them,
by myself and themselves, or by my and their deputy or deputies, servants or
agents, or such others as I, the said Joseph Manton, my executors, admi-
nistrators, or assigns, should at any time agree with, and no others, from time
to time and at all times thereafter during the term of years therein expressed,
should and lawfully might make, use, exercise, and vend, within England,
Wales, and the Town of Berwick-upon-Tweed, my Invention of "AN IMPROVE-
MENT IN TELESCOPES;" in which said Letters Patent there is contained a proviso,
obliging me, the said Joseph Manton, by an instrument in writing under my
band 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 His Majesty's High Court of Chancery within two
calendar months next and immediately after the date of the said rocited
Letters Patent, as in and by the same, reference being thereunto had, will
more fully appear.

page_text: NOW KNOW YE, that in compliance with the said proviso, I, the said
Joseph Manton, do hereby declare that my said Invention or improvement
consists in making air-tight exhausted telescopes or air-tight unexhausted
telescopes of every description, and that my said Invention or improvement is
particularly described in these Presents, and in the several Drawings or
sections hereunto annexed, with sundry references thereto, that is to say:―
The Figure 1st represents a reflecting telescope, which may be exhausted
or remain air-tight and unexhausted. a, a, a, a, a, a, an additional cap to
inclose the eye piece and breech of the telescope, the joint of the screw being
kept air-tight by means of a prepared collar of leather between them. The
leather that tho joints are to be kept air tight by must be soked in a mixturo
of two parts mutton suet and one part bees-wax melted together, or any
other substance or composition fit for the purpose. The best leather for tho
purpose is thin calf skin. d, e, two parallel glasses with leathers prepared
and put between them and their bearings to keep them air-tight; 0, 0, 0, 0,
two screwed rings with leathers prepared in them for screwing down tho
glasses or their leathers and bearing; 1, 1, 1, the screw for adjusting the small
speculum, the cylinder part of the screw being kept air-tight by passing
through the collars of leather g, 9, 9, 9, (prepared as before described) in the
tube h, h, h, h; 2, the stud which the adjusting screw passes through; x,
the cap for screwing up the collars of leather; m, the mill'd head for turning
the adjusting scrow; j, the screw through which the air passes while being
exhausted; it must have a collar of leather under its head, and when done is
screwed tight to keep out the external air; d, the scrow by which the
telescope is connected to the apparatus for exhausting and screwing up the
screw j;k, a cap to prevent the screw j from being disturbed.
Figure 2nd represents a refracting telescope, which may be exhausted or
remain air-tight and unexhausted, the object glass being moved instead of the
eye piece for adjusting the instrument. The outside tube a, a, a, a, of
the telescope must be made of metal, as free from pores as possible, to
keep the external hir from entering. 6, b, b, b, a tube to slide within tho
outer one carrying the object glass, which is adjusted by means of the screw
c, c, c, passing through the stud 2, which communicates to the inner tube, and is
kept air-tight by the same means as the adjusting screw, described in Fig. 1st.
, the cap for screwing up the collars of leather; m, the mill'd head for
turning the adjusting screw; d, d, two parallel glasses to preserve the
vaccuum kept air-tight by collars of leather between the joints, in the same
manner as the glasses described in Figure 1st; o, o, o, o, the screwed rings

page_text: for confining the glasses described in Fig. 1st; E, the parts for exhausting
the telescope, as described in Fig. 1st.
Fig. 3rd represents an eye piece for a refracting telescope, to be exhausted
or to remain air-tight and unexhausted where portability is required, and
the body of the telescope cannot be conveniently kept air-tight. a, a, a, a,
the outside tube, made without joints, and as free from pores as possible;
b, b, b, b, two tubes to fit in the outer one, and to hold the glasses in the usual
manner; the tubes must have channels made in them to let the air pass from
them when being exhausted. c, c, two parallel glasses to keep the vaccuum,
with collars of leather, in the manner as before directed; 0, 0, 0, 0, the
screwed rings for confining the glasses, as described in Fig. 1st; d, the parts
for exhausting, as before described.
Fig. 4th represents an opera telescope, which may be exhausted or remain
air-tight and unexhausted, the object glass moving instead of the eye piece,
as described in Fig. 2nd. a, a, a, a, the tube, made of metal, and free from
pores; b,b,b,b, the tube sliding in the outer one, which carries the object glass;
2, the stud, which is fixed to this tube for the adjusting screw to pass through,
and is adjusted in the same manner as described in Figure 2nd, the cylinder
part of the adjusting screw being kept air-tight by passing through collars
of leather in the same manner; x, the cap for screwing up the collars of
leather round the adjusting screw; m, the mill'd head to turn the adjusting
screw, as before described; c, a parallel glass to keep the vaccuum, with
leather between its bearings, as described in Fig. 2nd; d, the concave eye
glass, which also serves to keep the vaccuum in the same way, with leather. in:
its joint; 0, 0, 0, 0, two screwed rings for confining the glasses, as described
before; E, the parts for exhausting, as before described.
Fig. 5th represents the instrument which is applied to the air pump when
the telescope is to be exhausted for screwing up the screw j, Fig. 1st,
after the telescope is exhausted. a, a, a cylinder made of steel passing
through collars of prepared leathers in the tube b, b, b, b, and turned round by
the thumb piece c, c; d, d, d, d, the channell for the air to pass through from
the telescope to be exhausted into the air pump; e, the screw to connect the
apparatus to the air pump; f, the screw to connect the telescope to the
instrument. The advantages of air-tight exhausted telescopes are, that
the speculums in reflectors will not be so liable to tarnish, and the glasses in
reflectors will be preserved longer clean, and the air damps and dust will be
completely excluded. It will be of great utility if telescopes are made on the
air-tight construction without exhausting them, but if they are exhausted, the

page_text: nearer they are a perfect vaccuum the more clear and distinct objects will be
In telescopes which are required to slide into a' small compass it will
be an advantage to make the eye pieces only air-tight on this construction,
that they may be exhausted, if required, the same as the telescopes, by means
of an air pump, syringe, or any other instrument or machine fit for the
purpose.
The form and manner of making these telescopes may be varied, and the
manner of adjusting the focuses may also be varied. I intend to have
the tubes and metal part of these telescopes maile of brass, as I consider it the
best metal for the purpose, but other metals may be used for these purposes;
however, the greatest care should be taken that the metal which is used for
these telescopes should be as free from pores as possible. When telescopes
are more than four inches diameter, the large glass which covers the end to
keep out the external air should bo arched, to support the pressure of the
atmosphere when they are exhausted; but when they are four inches and
under, they may be made flat, provided the glass is of a sufficient thickness
not to bend when the telescope is exhausted; but in telescopes which are
made air-tight, and not exhausted, the large glass which covers the end may
in all sizes be made flat.
In witness whereof, I, the said Joseph Manton, have hereunto set my
hand and scal, this Twenty-second day of March, in the year of our
Lord One thousand eight hundred and ten.
JOSEPII (L.B.) MANTON.
Signel, sealed, and delivered in the presence of
JONAS WIGLEY.
EDWO PLOMER.
AND BE IT REMEMBERED, that on the same Twenty-second day of
March, in the year above mentioned, the aforesaid Joseph Manton came
before our Lord the King in His Chancery, and acknowledged the Specifi-
cation 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 same Twenty-second day of March, in the year above written.