AN IMPROVED ASTRONOMICAL INSTRUMENT FOR EXHIBITING THE POSITION OF THE HEAVENLY BODIES WITH RELATION TO THE EARTH
Year: 1873

page_text: PROVISIONAL SPECIFICATION left by Walter Marsham Adams at the
Office of the Commissioners of Patents, with his Petition, on the
4th April 1873.
I, WALTER MARSHAM ADAMS, B.A., late Fellow of New College,
Oxford, of the Arundel Club, Salisbury Street, Strand, in the County of
Middlesex, do hereby declare the nature of the said Invention for "AN
IMPROVED ASTRONOMICAL INSTRUMENT FOR EXHIBITING THE POSITION OF THE
HEAVENLY BODIES WITH RELATION TO THE EARTH," to be as follows :—
"This Invention has for its object" an instrument for exhibiting the
"motion and position of the heavenly bodies relatively to any point on
"the surface of the earth, and for embodying the various conceptions
necessary for nautical astronomy."
"
The apparatus consists in the first place of a stand carrying a globe
mounted somewhat like a sea compass, that is to say, the stand has fixed
to it a rigid vertical semicircle, at the ends of which are pivots carrying
slides which support a circular arc. A diameter of this circular arc
coincides with the axis of the globe.

page_text: The axis on which the globe is capable of revolving is a rigid wire
fixed in the above-mentioned circular arc. The globe occupies the
middle portion of the axis, and is therefore concentric with the circular
arc. Outside the globe there is a circle concentric with it, which is also
capable of revolving on the axis. This circle carries a slide to which a
blunt pointer is fixed. The pointer has a screw point, which when
screwed out presses against the globe, thereby fixing the position of the
slide and circle relatively to the globe. The point at which the pointer
touches the globe marks the position of the observer on the earth. By
moving the slide round the circle, and by turning the circle round on
the axis, the pointer can be set to any point on the globe. The slide
also carries two circular arcs or arms, which in their turn carry two
parallel circles of which the pointer is a pole. The size and position of
these circles is such that they mark the real and apparent horizon of the
observer. These circles are split to allow of their passing the axis. The
circle corresponding with the apparent horizon is carried by screws, so
as to allow of its position being altered to correct for the dip of the
horizon.
Next outside the circle carrying the pointer is another circle con-
centric with it, and the globe which is also free to turn on the axis.
Sliding on this circle and on each other are two other "great" circles
which mark the equator and ecliptic. At the pole of the ecliptic is
pivotted a quadrant of a great circle, which is used to find the solar
latitude and longitude; or, the pivot may be moved 5° from the pole,
and the quadrant may have sliding upon it a metal disc, so as to mark
the position of the moon. On the ecliptic itself is a short circular arm
at right angles to it, capable of sliding on it, on which slides another
disc representing the sun. The discs representing the sun and moon
can thus be slid up or down from the ecliptic, so as to shew the positions
of the sun and moon at different times of the year and month, and the
corrections for refraction and paralax. The circle forming the ecliptic
is made in two parts, sliding the one on the other; one part is marked
with the zodiac and the other with the months.
Outside the circle carrying the equator and ecliptic, and concentric
with it is a spherical framework of wires, each wire being a meridian
circle. These wires carry star-shaped plates of metal representing the
principal stars or the constellations. Halves or other portions of the
wires may be cut away for convenience sake. The spherical framework

page_text: may be made in two halves united by screws, so that it can be removed
at pleasure.
All the bearings of the circles on the axis, and all the slides may carry
set screws, so that any of the circles may be set to the axis independently
of the others, and the slides set on the circles. The circles may also be
graduated.