Improvements in or relating to Sun-dials.
Year: 1896

page_text: Date of Application, 8th Feb.. 1896-4ccepted, 6th June, 1896
COMT DEED ST
Improvements in or relating to Sun-dials.
A communication from LEO BRAUN, Merchant, of Uhlandstrasse, 10, Dresden A,
in the German Empire.
I ALFRED JULIUS BOULT of 323 High Holborn County of Middlesex,
Chartered Patent Agent 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 magnetic sun-dial with a dial secured to the magnet-needle is distinguished
by the dial being covered by an opaque disc with a setting-line and a slit wicket or
transparent portion for enabling the dial-markings to be read, and by the half of
the housing cover, which is opened when the apparatus is in use standing up from
the opaque disc allowing a ray or beam of light to pass through a slit in the
up-turned half and on to the setting line, wicket and dial markings.
Further peculiarities and properties of this improved instrument will be
explained, in their proper place in the following description.
The object of the improvement is to provide a simple and reliable instrument and
more particularly one which may be used by an inexperienced person.
In relation particularly to this latter point, it is to be remarked, that, hitherto,
the use of this class of instrument has required a certain knowledge of astronomy,
in the absence of which there is considerable liability to erroneous readings.
The new instrument is to be particularly recommended in the form of a pocket
sun-dial, in which case its simplicity and handiness are specially noteworthy.
It may also, however be constructed and used as a fixed horizontal sun-dial, in
which case the casing must be mounted on a vertical pin upon a suitable base-
plate.
In the accompanying drawings, the invention is illustrated in portable form, in
elevation, plan, and perspective respectively in Figs. 1 to 3; while Fig. 4 shows in
elevation a somewhat modified form of construction of the device.
Upon the bottom of the casing A is mounted a pin a whereon in well-known
manner, the magnetic needle b is pivotted. To the magnetic needle the dial c is
fastened in such manner that a diametrical line passing through the 12 o'clock
point on the dial makes with the needle an angle equal to the angle of magnetic
deviation as indicated in Fig. 2.
The divisions of the dial may be arranged to give the solar time, or the mean
time of the locality, or the mean European time (as used on railways in Germany
and other countries). If the slit in the raised half of the cover is a perpendicular
one the dial is provided with several concentric divisions (Fig. 2) in order, with
relation to the ecliptic to obtain throughout the whole year, at least approximately
correct time indications. These divisions, it is true, are only available for
a certain geographical latitude; but the differences, inside of 3 degrees of latitude,
may be neglected. The dial can also be exchangeable; and in that case, for
each season, and for different degrees of latitude, special dials are prepared.
With inclined slot in the raised half of the cover, one single division suffices for
all seasons; if the inclined slot is adjustable, the same dial is available for different
latitudes.
Above the dial lies the covering disc d, whereof the edge is held by the
casing A. This disc consists of opaque material (metal, cardboard, celluloid, or

page_text: ground-glass). In metal or cardboard, the reading opening or wicket d' (or several
such openings d-d) are formed and the opening (or openings) may be glazed;
if celluloid, dead or ground-glass or even mica is the material of which the disc d
is formed, the corresponding portions (d' or d'-d') are made transparent while the
rest of the disc is left opaque.
If the dial is provided with only a single division, the disc d has also only one
wicket. If there are several divisions, a greater opening extends over all of
them; in that case there must be written instructions on the edge of the reading
opening, indicating which of the said divisions is to be used for the reading. This
wicket may also be partially covered by a slide in such a manner that only one
division is exposed at a time.
If there are several divisions, it is best to arrange the different wickets d'- d
(Fig. 2) in such a manner that each division is below one of the wickets. In this
case, another disc e with openings el el is provided over d and is capable of rotating
in a groove of the case A. During this rotation, which is facilitated by notches
or hollows e for the finger-nails, the wickets appear successively at the opening ele..
In this case, also, written indications upón e and d distinguish the wicket to be
employed.
Of importance, in respect of the employment of the instrument, are the various
radial setting lines fupou the disc d. Their object is to enable the light-ray, from
the slit in the raised half-covering to fall upon a particular place of the covering
disc d. If the latter is rotatable the adjustment of the line fis effected in relation
to the radial line f¹, on the disc e (Figs. 2 and 3) which is fixed after having been
previously adjusted according to the season of the year. Without the lines f
and f, it would be impossible to bring the said light-ray exactly to bear upon that
division, whereon the time must be read.
The case A is closed at the top by the cover, whereof one half g is fixed, while
the other half gl is jointed thereto in such manner that it can be raised into
a perpendicular position. In this latter part is formed the radial slot h, which
enables the time to be read off, on the dial, by means of the light-ray which passes
through said slot. The slot is vertical in the centre of the vertically raised half-
cover (Figs. 1-3) if the dial has several divisions for the different seasons of the
year. If a single division is used the slot is adjusted to make an angle to the
equator (Fig. 4) equal to the geographical latitude of the place expressed as an
angle. To enable such an instrument to be used in different latitudes the inclined
slot is made adjustable. To this end it is formed in a sector /', pivotted on a pin ³,
mounted in 9, and covers the sector-shaped aperture in the raised half-cover.
This aperture is of such size as to allow the slot to be adjusted for all angles
required; and the adjustment is effected according to a vernier or scale fixed or
engraved on the curved border of the sector . If the slot is inclined, the
cover g-g' must be rotatable, in relation to the line for the lines and f¹, i.e. in
relation to the wicket, because the slot must in the afternoon lie on the side of the
perpendicular centre-line - (Fig. 4) opposite to that where it was in the
morning. To this end the outwardly turned edge of the casing A fits into
a groove k formed around the cover g so that the entire cover rotates upon the
said casing, and a pin on A, in conjunction or combination with two pro-
jections on k (whereof one only is shown in Fig. 4) limits the rotation to 180°.
For the purpose of enabling the time to be read off, when the sky is clonded,
a ring is also provided, to cast a shadow. This ring lies in the vertical plane
passing through the sloth or in the inclined plane passing through the slanting
slot; and it is rotatable in the eyelet , so that it may be laid down flat
upon g.
The working of the instrument is based upon the fact that the magnetic-needle,
carrying the dial will always point in the same direction, while the casing of the
instrument, with the covering disc d, with the setting lines ff', and with the
sloth in g is turned. When it is turned into such a position that the sun's ray
passing through the slot h in the raised part of the cover g' and thrown upon the

page_text: setting line ff and through the wicket, falls upon the division of the dial, the
time can be read off, from the latter.
In order to prevent errors, the hours before and after midday may be printed in
different colours.
If the sky is cloudy, the ring i is raised into such a position that both its sides
are equally lighted and its shadow passes through the slot h, the time being then
indicated by the division under the setting-line.
Having now particularly described and ascertained the nature of the said inven-
tion as communicated to me by my foreign correspondent, I declare that what I
claim is ;-
1. A magnetic sun-dial, characterised by the dial (c) secured to or carrying
a magnet being covered with an opaque disc such as d above which is so arranged
& case-cover such as 99' one half (9) of which is provided with a slot such as h
and may be raised into a vertical position that the light-ray falling through the
slot in the raised half-cover can be made to coincide with a radial setting-line (f)
upon the opaque disc (d) for the purpose of indicating the figures which appear at
a wicket or transparent portion (d) of said disc.
2. A magnetic sun-dial such as described in Claim 1 characterised by the dial
being provided with several concentric divisions for the purpose of enabling it to
be used in different seasons or at different places substantially as described.
3. A magnetic sun-dial such as described in Claim 1 characterised by the opaque
disc d being rotatable and provided at different places with transparent portions or
wickets such as d d d d enabling the disc to be rotated so that each of the
wickets may be adjusted to a position convenient for the reading of the divisions
described in Claim 2 for which purpose the wickets are each over one of the
division zones that is to say at a distance from the centre differing from all the
others and are visible when presented at an opening eel of a fixed disc such as e
which has a setting line f¹ substantially as described.
4. A magnetic sun-dial such as described in Claim 1 characterised by the slot h
in the raised half-cover (g) being set aslant in accordance with the latitude of the
locality where it is used and the cover (9 g¹) being rotatable in relation to the
casing of the instrument, to an extent of 180° substantially as described.
5. A magnetic sun-dial such as described in Claim 1 characterised by the slot (h)
for enabling the same sun-dial to be used at different latitudes being adjustable
for which purpose it is formed in a sector such as h' adjustable in relation to
a sector-shaped opening such as h h in the semi-cover (gl) substantially as
described.
6. A magnetic sun-dial such as described in Claim 1 characterised by a ring (i)
pivotted to the half-cover (9) and capable of being turned up so as to lie in the
plane passing and project its shadow through the slot and thereby enable the
instrument to be used when the sky is over-clouded substantially as described.
7. The combination and arrangement of parts constituting the complete sun-dial
substantially as described and illustrated in the accompanying drawings.
Dated this 8th day of February 1896.
BOULT & WADE,
Agents for the Applicant.