An Improved Armillary Sphere.
Year: 1891

page_text: Date of Application, 17th Sept., 1891
Complete Specification Left, 14th May, 1892-Accepted, 18th June, 1892
PROVISIONAL SPECIFICATION.
An Improved Armillary Sphere.
I, JOHN SAMUEL SLATER of the Civil Engineering College, Calcutta, India,
Professor of Civil Engineering, do hereby declare the nature of this invention to
be as follows:-
This invention relates to an improved armillary sphere designed to illustrate the
apparent motions of the sun and of the stars in different latitudes, to indicate
the times of rising and setting of the sun and of stars whose declination and
right ascension are known, to shew the apparent position of the ecliptic at any
particular time on any day of the year, and for other like studies in connection with
the motions of celestial bodies.
In an armillary sphere constructed according to this invention the annular rings
or circles and parts by reference to which the motions of celestial bodies are studied,
are supported by a pivoted arm which moves over and can be by a suitable clamp
fixed at any desired position on a scale graduated from the centre of motion of the
pivoted arm to represent degrees of latitude. A disc representing the sensible .
horizon is also provided and is arranged concentric with the aforesaid annular rings
or circles hereinafter referred to as circles. The celestial equator and the meridian
are represented by fixed circles and another fixed circle serves as a declination
circle, each of these circles being in a plane at right angles to those of the
other two.
The ecliptic is represented by a movable circle having twelve divisions for the
twelve signs of the zodiac, and situated in a plane inclined to that of the circle
representing the equator at an angle equal to the inclination of the ecliptic to the
equator. This circle is carried by external peripheral attachments or clips in
which it is free to slide so that it can be rotated about its centre in its own plane.
These attachments are rigidly connected to a ring carried by similar attachments
on the equator circle, by which means the ecliptic circle can be moved around the
equator circle.
.
The disc representing the sensible horizon has the points immediately opposite
the meridian circle marked respectively "North " and "South" while those
opposite the declination circle are marked "East" and "West." It is preferably
graduated from zero at the east and west to ninety at the north and south points
and is mounted between two pivots situated respectively at the "East"
"West" points. The disc is also provided with a plumb weight to bring it to a
horizontal position.
and
The meridian circle is graduated preferably from zero at the point where it meets
the celestial equator to ninety at the points where it meets the declination circle
being thus divided into four quadrants.
The equator circle is graduated to represent 24 hours and, if desired, fractions
of an hour.
The points where the declination circle and the meridian meet represent
respectively the north pole and the south pole, being independent of the points
marked "North" and "South" on the horizon disc, which simply serve to represent
the direction of these points to an observer supposed to be standing at the centre of
the said disc.
The radius of motion of the pivoted arm carrying the circles and other parts
passes through the north and south poles on the meridian circle.
The declination circle need not itself be graduated, the declination being easily
read at any point of the equator by means of two segmental quadrants pivoted at
one end one at the north pole and the other at the south pole so that they can be

page_text: rotated freely on opposite sides of the equator, to which their free extremities
extend. These quadrants are graduated, preferably from zero at the equator to
ninety at the poles.
To enable altitudes to be read off, the disc representing the sensible horizon
carries at its centre a vertical graduated protractor-like piece mounted so as to be
capable of turning freely about a vertical axis, passing through the centre of the
horizon disc.
Dated this 17th day of September 1891.
W. LLOYD WISE,
Per F. J. Brougham,
46, Lincoln's Inn Fields, London, W.Č., Agent for the Applicant
COMPLETE SPECIFICATION.
An Improved Armillary Sphere.
I, JOHN SAMUEL SLATER, of the Civil Engineering College, Calcutta, India,
Professor of Civil Engineering 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 an improved armillary sphere designed to illustrate the
apparent motions of the sun and of the stars in different latitudes, to indicate
the times of rising and setting of the sun and of stars whose declination and right
ascension are known, to shew the apparent position of the ecliptic at any particular
time on any day of the year, and for other like studies in connection with the
motions of celestial bodies.
In the accompanying drawings
Fig. 1 is a side elevation,
Fig. 2 a front elevation, and
Fig. 3 a detail hereinafter referred to, of an armillary sphere constructed
according to this invention, the various parts being shewn in positions corresponding
approximately to latitude 52° N.
Fig. 4 is a detail hereinafter referred to.
The annular rings or circles and parts by reference to which the motions of
celestial bodies are studied, are supported by a pivoted arm A arranged to move
over a graduated scale B adapted to be fixed by a suitable clamp A' at any desired
position on the said scale. This scale B is secured to or marked upon a projecting
arm B on a suitable stand or support B2, and is graduated from zero to ninety
degrees from a horizontal line that would pass through the pivot of the arm A if
projected, and which is marked zero, these graduations representing north latitude
above the said horizontal line, and south latitude below the said line. A disc C
representing the sensible horizon, is arranged concentrically with the aforesaid
annular rings or circles, hereinafter referred to as circles. This disc C is shewn
separately in plan in Fig. 3. The celestial equator and the meridian are represented
by fixed circles D and E respectively and another fixed circle F serves as a
declination circle, each of these circles being, as shewn, in a plane at right angles to
those of the other two.
The ecliptic is represented by a movable circle G having twelve divisions for
the twelve signs of the zodiac, and situated in a plane inclined to that of the circle D
representing the celestial equator, at an angle equal to the inclination of the ecliptic
to the equator. This circle G is carried by external peripheral supports or clips G¹
in which it is free to slide so that it can be rotated about its centre in its own plane,
clamping screws G' being provided for holding it securely in the supports G¹.
These supports are rigidly connected to a ring H carried by supports G that fit
over the edge of the celestial equator circle D and are adapted to slide round the
same. By these means the ecliptic circle G can be moved round the celestial
equator circle D, the ring H serving as a hold for the fingers, and obviating the

page_text: necessity for touching the circle G when it is only desired to move the circle G
around the circle D without moving it round its own centre.
The disc C representing the sensible horizon, has the points immediately opposite
the meridian circle, marked respectively N (north) and S (south), while those
opposite the declination circle F are marked E (east) and W (west). It is
preferably graduated from zero at the cast and west points, to ninety at the north
and south points, and is according to this invention hinged or mounted between two
pivots C situated respectively at the "East" and "West" points. The disc C is
provided with a plumb weight I to maintain it in a horizontal position, this weight
being adjustably held between two brackets I' on the lower part of the disc C by
means of set screws I. Thus it will be seen that the disc constitutes a movable
horizon that will adapt itself automatically to the selected latitude.
The meridian circle E is graduated preferably from zero at the points where it
meets the celestial equator circle D, to ninety at the points where it meets the
declination circle, being thus divided into four quadrants, as shewn.
The celestial equator circle D is divided into twenty-four equal parts representing
24 hours, which parts, if desired, may be further subdivided into fractions of an
hour, the graduations being preferably from the point where the meridian and the
celestial equator circles meet towards S on the disc C, round the circle towards W
where the division corresponding to the 6th hour is situated and so on to the
starting point which will be marked 24. The declination circle F and the meridian
circle E are provided at the points where they meet, with nut-like pieces J having
transverse slots into which the said circles enter, the four unremoved portions of
each of the pieces J fitting in the four angles formed by the meeting of the said two
circles, as shewn.
"
The points where the declination circle and the meridian circle meet, represent
respectively portions of the north pole and the south pole, being independent of the
points marked "North" and "South on the horizon disc C, which simply serve
to represent the direction of these points to an observer supposed to be standing at
the centre of the said disc.
The radius of motion of the pivoted arm A carrying the circles and other parts
passes through the north and south poles on the meridian circle.
The declination circle I need not be graduated, the declination being easily read
at any point of the equator by means of two segmental quadrants K, K each
pivoted at one end, one of these, namely K, being pivoted at the north pole, and
the other K being pivoted at the south pole, so that they can be rotated freely on
opposite sides of the equator circle D to which their free extremities extend. The
pivots consist preferably each of a long screw L whose head is cut away on one
side as shewn in Fig. 4, and is let in to the end of the quadrant so as to be flush
with the inner surface thereof, the side of the head from which a portion has
been cut away, fitting against the face of the recess into which the head enters.
The stem of this screw passes through the piece J and enters a milled nut L'
by which it is held in position. The quadrants K K' are graduated, preferably
from zero at the end next the celestial equator circle to ninety at the poles. To
enable altitudes to be read off, the disc C representing the sensible horizon, carries
a vertical graduated protractor-like scale M (hereinafter called for distinction the
circle of altitude) mounted on the said disc so as to be capable of turning freely
about a vertical axis passing through the centre of the horizon disc.
parts C and M are connected together by a screw threaded pin extending from the
bottom of the plate on which the scale M is marked, at a point midway between
This pin is
the extremities thereof, and passes through the centre of the disc C.
provided beneath the disc with a nut N by turning which the circle of altitude M
can be fixed in any desired position on the disc C, or can be released therefrom for
adjustment.
The
To use the instrument, the arm A is adjusted on the scale B to the division
corresponding with the degree of latitude with regard to which it is desired to
study the motions of the celestial bodies. An observer being supposed to be at a

page_text: point at the centre of the disc C or sensible horizon it will be seen that the north
pole is above or below the horizon at an altitude equal to the chosen latitude, and
that the celestial equator circle is a circle passing through the east and west points,
cutting the meridian of the observer at a point equal to the latitude of the place
measured from the zenith.
To find the declination of the sun or to find the time of sunrise on any day of
the year, the ecliptic circle G is first moved round till the first point in the
constellation of Aries hereinafter referred to as the "first point of Aries" comes
opposite the hour division on the celestial equator circle that corresponds with
the right ascension of the sun on that day, as given in astronomical tables, or as
calculated approximately on the assumption that the right ascension increases at
the rate of four minutes for each day after the vernal equinox. The declination
of the sun can then be read off by observing the point where the ecliptic circle G
cuts the meridian circle E, the observation being made from or relatively to the
centre of the horizon disc C. The time of sunrise can then be found by moving
the declination quadrant K or K¹, as the case may be, round towards the point
marked E on the disc C, until the degree thereon corresponding with the declina-
tion is level with the said disc. By reading off the division on the celestial
equator circle at which the quadrant has arrived, the number of hour divisions
separating this point from the meridian towards S, can be readily ascertained,
and as the sun is on the meridian at noon, it follows that it rises that number of
hours before noon to which the hour divisions correspond.
Now
The time of rising, and also the path, of stars whose declination and right
ascension are known, may also be found. This is perhaps best illustrated by an
example. Thus to find the time of rising of a star whose declination is 20° N.
and right ascension 14 hours, on the 21st June for a latitude 40° N. On the
21st June, the right ascension of the sun will be about 6 hours, and as the right
ascension of the given star is 14 hours it will be 8 hours behind the sun.
adjust the declination quadrant K so as to shew the star just on the horizon
towards E for, say, 40° N. latitude. It will be seen that the declination quadrant
in this position cuts the celestial equator circle at about 16 hours. The sun being
8 hours in advance would be at 24 hours, or half an hour after noon. The star
would therefore rise about 12.30 p.m. Similarly by carrying the declination
quadrant to the west, it will be observed that when the star sets the declination
quadrant points to about 7 hours; the sun would be 8 hours in advance or at 15
which represents 3.30 a.m. If the position of the star referred to at 19 o'clock at
night on the same day be required, move the declination quadrant to 2 hours on
the celestial equator circle that is 8 hours behind the sun, which would, at that
hour, be at 10 hours after noon. The circle of altitude is then caused to revolve
until it intersects the 20° graduation on the declination quadrant. The inter-
section shews the altitude at this hour; and the point where the circle of altitude
cuts the graduated rim of the horizon disc, shews the angular distance of the star
from the west point.
The apparent diurnal motion of the ecliptic can be readily seen if the ecliptic is
made to revolve from E. to W. At noon at the vernal equinox, the first point of
Aries is on the meridian, and in this position it will be seen that the ecliptic lies
over the horizon from N.E. to S.W. At six o'clock in the evening, at the vernal
equinox, the first point of Aries will be at the west point; and the ecliptic will cut
the meridian 23° north of the celestial equator, and at that hour Cancer will be
on the meridian. At midnight the first point of Aries will be at twelve hours on
the celestial equator, and Libra will be on the meridian, the ecliptic in this position
lying over the horizon from S.E. to N.W. At six o'clock in the morning the first
point of Aries will he in the east, and Capricornus will be on the meridian,
about 23° south of the celestial equator. To find the position of the ecliptic on
any day of the year at any time, in any latitude, say for example the position for
an observer in latitude 52° N. at 10 p.m. on the 7th of August. Making the usual
calculation for the right ascension of the sun, this will be found to be about 9 hours

page_text: 16 minutes. At 10 p.m. the sun will be at 10 hours on the celestial equator, and
the first point of Aries will be 9 hours 16 minutes in advance, that is at 19 hours
16 minutes. Place the ecliptic so that the first point of Aries is at this hour,
and the other signs will then be found to be in place.
There are various other purposes to which this armillary sphere may be put,
such as tracing the inclination of the path of the sun on any day with reference to
the celestial equator, this inclination being a factor in computing the equation of
time. Enough, however, has been explained to enable persons accustomed to
astronomical work to make use of the instrument with facility.
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 :-
1. An armillary sphere for illustrating motions of celestial bodies, carried by
a pivoted arm arranged to move in a vertical plane over a scale graduated to
represent latitude, substantially as described.
2. An armillary sphere for illustrating motions of celestial bodies, carried by a
pivoted arm, arranged to move in a vertical plane over a scale graduated to
represent latitude and provided with a pivoted weighted disc that represents the
sensible horizons, and is adapted to remain in a horizontal position in all positions
of the armillary sphere substantially as described, whether or not the said disc be
provided with an adjustable circle of altitude such as M.
3. In an armillary sphere carried by a pivoted arm moving over a scale repre-
senting latitude, a circle representing the ecliptic arranged to be turned about its
own centre and also around the equator circle, and means for supporting the
same, substantially as described.
4. In an armillary sphere of the kind referred to in Claim 2, the combination
with circles representing respectively the equator, the meridian and the ecliptic, of
movable declination quadrants pivoted at the poles, substantially as described.
5. My improved armillary sphere constructed substantially as described and
shewn.
W. LLOYD WISE,
Per F. J. Brougham,
46, Lincoln's Inn Fields, London, W.Č., Agent for the Applicant.