Improvements in Levels and Surveying and Astronomical Instruments.
Year: 1889

page_text: Date of Application, 29th July, 1889
Complete Specification Left. 7th Aug. 1889-Accepted. 23th Sept. 1889
PROVISIONAL SPECIFICATION.
Improvements in Levels and Surveying and Astronomical
Instruments.
JOHN SHORT 2 Gladstone Street Southwark London S.E. Mathematical Instrument
Maker do hereby declare the nature of this invention to be as follows:-
This invention relates to an improvement in Levels and Surveying Instruments and
is equally applicable and of service in the construction of Astronomical Instruments.
It comprises the combination of two centres or axes of rotation for the telescope, and
the limb or circle of the instrument, these two centres working and fitting one within
the other. Each of these two centres has its axis of rotation at a different. angle to
the visual axis or line of the tolescope, in relation to the angle of the axis of rotation
of the other centre.
A circular plate or limb is attached to one of these two centres, on which plate are
marked, graduations, which shew the slope or Vertical inclination of distant objects
observed through the telescope, or the angular Valve or expression of this slope or
inclination of the distant objects.
The combination of these two centres in the manner described secures a Vertical
depression or elevation to the telescope at the same time that it is moved in a hori-
zontal direction.
COMPLETE SPECIFICATION.
Improvements in Levels and Surveying and Astronomical
Instruments.
I, JOHN SHORT of 2 Gladstone Street Southwark London S.E. Mathematical
Instrument Maker 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 :-
This invention relates to improvements in Levels, and Surveying and Astronomical
Instruments.
It has for its object the accurate measurement of very small amounts of Vertical
depression or elevation, and expressing them by graduations on an arc or circle in
such a manner as to be very easily read.
It comprises the combination of two centres, or axes of rotation, for the telescope
and the limb or circle of the instrument, these two centres working and fitting one
within the other. Each of these two centres has its axis of rotation at a different
angle to the Visual axis or line of the telescope, in relation to the angle of the axis of
rotation of the other centre.
A circular plate or limb is attached to one of these two centres, on which plate or
limb are marked, graduations, which shew the slope or Vertical inclination of distant
objects observed through the telescope, or the angular Valve or expression of this
slope or inclination, or, the angular difference which exists between any two or more
distant objects. The combination of these two centres in the manner described,
secures a Vertical depression or elevation to the telescope at the same time that it is
moved in a horizontal direction, and, this resulting Vertical depression or elevation, or
angular difference, is expressed as aforesaid by the graduations on the limb or circle
attached to one of the two axes or centres of the instrument. In order that my said
Invention may be fully understood; I annex a drawing of those parts of the instrument
which are essential to the principle involved.

page_text: DESCRIPTION OF THE DRAWINGS.
с
A. A. is the inner axis or centre of the instrument to which the stage or platform (
is attached, on this stage the telescope of the instrument is permanently mounted or
fitted, but, the telescope is not shewn in the drawing it not being essential to the
proper description of the Invention. B. B is the outer axis or centre of the instrument,
to which the limb or circle D is attached, this limb or circle D is that on which the
graduations are marked or engraved which shews the slope or gradient of the objects
observed through the telescope.
The stage C with the telescope attached always revolves with the inner centre A
when that is rotated, and the graduated limb D always revolves with the outer centre B
when that is rotated, the stage C with the telescope and the graduated limb D revolve
together on the outer centre B if a clamp is set (not shewn in the drawing) which
holds the stage C and the limb D firmly together, when required.
E and Fare two parallel plates of brass or other metal, and G, G, are two of the
four milled head screws which keep these plates apart and by which the Level, or
other Surveying Instrument, set up in a truly level position as usual for the ordinary
purposes of Levelling or Surveying, the other two milled head screws G, G, are not
shewn in the drawing but, are identical with these two.
The outer centre B is fitted to and works in a taper hole that passes through the
whole length of the upper parallel plate E, and the inner centre A is fitted to and
works in a taper hole which passes through the whole length of the outer centre B,
but as stated before, the axis of rotation of these two centres is neither identical, nor
parallel one to the other for, the axis of the hole which passes through the whole
length of the centre B is at an angle at all times with the axis of the hole in the upper
parallel plate E, therefore is the horizontal motion of the telescope attached to the
stage converted into a small Vertical depression, or inclination, which is very
accurrately measured by and easily read at, the graduations on the limb D.
The fittings and mounting of the Level or other Surveying Instrument to which
this mechanical principle is applied, are of the general character common to such
instruments, and do not affect the inerits of this Invention.
And this combination of two centres or axes of rotation standing at different angles
to the line of a telescope, together with a graduated limb to express or indicate very
small angles can be equally as well applied to Astronomical Instruments and I
claim its use for them.
Having now particularly described and ascertained the nature of the said Inven-
tion and in what manner the same is to be performed, I declare that what I
claim is,―-
1st The use of two centres or axes of motion to Levels and Surveying and
Astronomical Instruments, working and fitting one within the other, but, each
centre having its axis of rotation at a different angle to the visual axis or line of
the telescope, in relation to the angle of the axis of rotation which the other centre
has in respect to the line of the telescope.
2nd The use of the graduated limb attached to one of these two centres, having
marked or engraved on it the slopes or gradients of objects viewed through the
telescope, or, the angular equivalents of these slopes or gradients.
Dated this 7th day of August 1889.
JOHN SHORT.