An Instrument for Finding the Altitude of Heavenly Bodies, especially applicable for Use at Sea.
Year: 1894

page_text: Date of Application, 10th Jan., 1894
Complete Specification Left, 10th Oct., 1894-Accepted, 22nd Dec., 1894
PROVISIONAL SPECIFICATION.
An Instrument for Finding the Altitude of Heavenly Bodies,
especially applicable for Use at Sea.
I, EDWARD AYEARST REEVES of The Royal Geographical Society, 1 Savile
Row, London, W. do hereby declare the nature of this invention to be as
follows:
An important object of this invention is to overcome the difficulty or impossibility
now experienced by mariners in taking altitudes by means of the sextant when the
horizon is obscure or invisible. In my instrument I do not use or need any horizon
to work from, but according to my invention I obtain the angle relatively to a
vertical line which is produced by a pendulum arrangement, in which the framing
carrying the vernier and the reflecting mirror (which answers in the sextant to the
so called index glass) swivels upon the horizontal axis of the telescope, the
graduated arc and the handle.
In one form of my instrument the graduated arc is arranged in the upper part of
same with the handle fixed by preference on the right hand side or end of the
horizontal axis of the telescope. On this axis swivels the vernier which has a
lower prolongation or arm in the lower part of which is mounted a pendulum. The
gudgeon of suspension of the latter carries a tooth wheel which gears with a pinion
on a spindle supported in bearings carried by the arm. On the outer end of this
spindle is mounted the reflecting mirror or index glass. The underside of the
telescope is near its horizontal axis of mounting cut away and one half of its inner
sectional area of vision is here taken up by a reflecting mirror placed at an angle of
about 45°.
In using this form of instrument (which is held in the right hand by the handle)
when the heavenly body is observed through the open or unobscured half space
adjoining the half circular mirror part, the vernier is taken hold of with the left
hand and moved till the image is seen in the telescope mirror by reflection from
the index glass in line with a central horizontal wire which crosses the slanting
mirror and simultaneously seen to coincide with the image seen by direct vision.
The vernier is then clamped and finally adjusted by a tangent screw.
Dated this 10th day of January 1894.
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.
COMPLETE SPECIFICATION.
An Instrument for Finding the Altitude of Heavenly Bodies,
especially applicable for Use at Sea.
I, EDWARD AYEARST REEVES of The Royal Geographical Society 1 Savile
Row London, W. 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 :-
An important object of this invention is to overcome the difficulty or sometimes

page_text: the impossibility now experienced by mariners in taking altitudes by means of the
sextant when the horizon is obscure or invisible but the instrument may also be
applied to other angle measuring purposes. In my instrument I do not use or need
any horizon, natural or artificial, to work from, but according to my invention I
obtain the angle relatively to a vertical line which is produced by a pendulum
arrangement in which the framing or radius carrying the vernier and the reflecting
mirror (which latter answers in the sextant to the so-called index glass) swivels
upon the horizontal axis upon which are fixed the telescope, the graduated arc and
the handle. The pendulum and the reflecting mirror are by preference both
mounted directly on the vernier radius and connected by wheel gearing or otherwise
in such manner as to move together. The underside of the telescope is at its end,
near its horizontal axis, cut away or chambered, and one half of its inner sectional
area of vision taken up by a reflecting mirror placed at an angle of about 45°, the
silvered back of said mirror lying in a diagonal passing through the axis. The
graduated arc may be arranged above the horizontal axis C, and the vernier radius
would then likewise be above it while the pendulum with the reflecting mirror
would be upon a lower prolongation of the vernier radius. But I prefer to have
the graduated are below the said horizontal axis, and the vernier radius upon which
the pendulum and the reflecting mirror are mounted will then also be below said
axis. Such an arrangement is shewn in the perspective view Fig. 1 of the accom-
panying drawing. Fig. 2 is a part end view and Fig. 3 a part side view partly in
section.
The graduated are A is on the triangular framing B in the upper end of which is
fixed the horizontal axis C. Upon the one end of the axis C is fixed the telescope D
and upon the other end the handle E for bolding the instrument by. The vernier
radius F swivels upon the axis C. On the vernier radius F are mounted the
reflecting mirror G and the pendulum H. The gudgeon or spindle H¹ of the latter
Figs. 2 and 3 carries two tooth wheels H' gearing with two tooth wheels G³ on the
gudgeon or spindle G¹ of the reflecting mirror G. Or instead of two sets of wheels
which are preferable for steady working I may use one such set. The silvered
back of the mirror G is in a diagonal crossing the centre of the axis. The
screws G serve for accurate adjustment in this respect. G' is a small counter-
weight which may be applied to an arm G on the frame of the mirror for equi-
poising it. The arm of the pendulum H is slotted at H* for permitting the
spindle G to work freely therein during the motion of the pendulum. The
spindles H¹ and G' have their bearings at one end in the vernier radius F and at
the other end in the staple or bracket F1 fixed on the radius or made in one
therewith. The position of the spindles G' and H' might be reversed but in that
case the pendulum would be shortened to the extent of the distance between the
said spindles and would then not need the slot H* but I prefer the arrangement
here shewn. A set screw or the like may be applied against one of the wheel
spindles in such manner as to clamp into each other the teeth of the wheels G'
and H and so fix the mirror G when the pendulum is clamped to the arm.
set screw N which is screwed through a lug on the back of the bracket F1 answers
this purpose when its point is made to enter a conical recess G* in the boss of the
mirror G. The radius F is fitted with screw F for final adjustment, with the
screw F for clamping it to the frame B, and with the screw F for entry with its
pointed end in a recess H in the pendulum H and to thus clamp it thereto when
the instrument is to be used as a sextant, or when out of use.
The
The telescope D is as shewn in Figs. 2 and 3 formed with a chamber D' open
below and with its slanting end open or cut off at an angle of about 45°. The right
hand half of this end opening is covered with a reflecting mirror D', the silvered
outer back of which lies in a diagonal through the axis C. The two bow springs L,
one at each side, hold the mirror D' in place and the four screws M serve to adjust
it accurately. The sliding eye piece tube D³ has a button D* which slides in a
length slot D' for the purpose of guiding it circumferentially and thus maintaining
the cross wires D' and D in right position for focussing. K is a well-fitting peg

page_text: with silvered knob at the end which reflects the light from the hole K¹ into the
interior of the telescope and upon the hair lines, as required at night.
The frame B may have legs B' for resting it in the box or on a table against
them and against the end of the axis C.
In using the instrument it is held in the right hand by the handle E and in a
nearly perpendicular position. Clamp the vernier radius at about the middle of
the arc, say at 50°, and release the pendulum H from the vernier radius F by
turning back the screw F and the screw N. It is easy to see if the instrument is
in the perpendicular position for in that case the images will move when vibrating
up and down parallel with the vertical wire D³ in the telescope. Now turn the
whole instrument upwards until the object observed is visible in the telescope by
direct vision through the uncovered part of the end opening in the chamber D¹ and
near the horizontal wire D°. Then loosen the clamp screw F by the left hand, and
the vernier arm F must be moved slowly forward or backward until the object
observed is again seen in the telescope by reflection from the mirror G and the
mirror in D'. When the two images, the one seen by direct vision and the other
by reflection, coincide in the central wires De D' clamp the radius F to the
framing B by means of the screw F and adjust accurately by means of the tangent
screw F until the two images are seen on the central horizontal wire D'or in their
vibrations pass that wire together. Then the angle of altitude is indicated on the
graduated arc A and is read off by the vernier in the usual manner.
To use the instrument for taking horizontal angles or as a sextant, clamp the
pendulum H to the radius F by means of the screw F and the recess Hand
tighten up the wheels G and H³ against each other by the set screw N. Then
taking the instrument in the right hand and holding it in the plane of the two
objects the angle between which is to be ascertained look through the clear opening
of the telescope at the right hand object. Next unclamp the radius F by means of
the screw F and move the vernier radius F until the image of the left hand object
appears in the mirror at D' or with absolute accuracy on the vertical wire D' with
the right hand object seen through the telescope. The objects are brought together
in the usual way by the tangent screw F'. The indication on the arc A is then
the angle between the objects.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is:
1. An instrument consisting mainly of two parts viz. (1) a frame with graduated
arc and a telescope with reflecting mirror said parts being fixed on an axis and
adapted to be held in the hand, and (2) a vernier radius swivelling on the axis
and upon which are mounted a swivelling pendulum and a swivelling reflecting
mirror actuated by the movements of the pendulum substantially as set forth.
2. In an apparatus of the character described the vernier radius F in combina-
tion with the mirror G and the pendulum H constructed and geared together as
shown and described.
3. The construction of instrument described with reference to the accompanying
drawing.
Dated this 10th day of October 1904.
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.