Improvements in Sun-dials.
Year: 1892

page_text: Date of Application, 27th Jan., 1892
Complete Specification Left, 3rd Oct., 1892-Accepted, 5th Nov., 1892
PROVISIONAL SPECIFICATION.
Improvements in Sun-dials.
I, JOHN RYDER OLIVER, of No. 25, Gwendwr Road, West Kensington, in the
Administrative County of London, C.M.G. and Major General Retired List, late
Royal Artillery, do hereby declare the nature of this invention to be as follows:-
This invention relates to improvements in sun-dials and it consists in the com-
bination of an arc or circle upon which the hours are marked and a gnomon of a
special contour. The arc in question is an equatorial one, and in respect of the
relative positions of it and the gnomon, the axis of the latter bisects the centre of
the former and is perpendicular to its plane. The hours are marked upon the
concave face of the arc (which is of the length necessary for that purpose), and are
indicated upon it by the passage of the edge of the shadow of the gnomon across an
equatorial line marked upon the said arc.
The contour of this gnomon may be described as the result of the revolution of a
certain curve about a polar axis. This curve is obtained by setting off along a
straight line, in both directions from an equatorial zero, series of abscissæ, and
laying off ordinates at right angles thereto. These abscisse are found for certain
dates at given intervals by multiplying the length of the radius of the equatorial
arc or circle by the tangent of the sun's declination for the particular date in
question. The ordinates are found by multiplying the same radius by the tangent
of the angular value of the equation of time. The curve is then drawn through the
series of points so found.
Perfect accuracy demands the use of two distinct gnomons, one for use from the
winter to the summer solstice, and the other for the following and equal term.
But if a single gnomon of mean contour be used, the error produced is so minute
that it is practically inappreciable.
The sun dial constructed as above described indicates true local mean time, but
the hour are may be set to indicate time according to any standard meridian
required.
Dated this 27th day of January 1892.
PHILLIPS & LEIGH,
Agents for the Applicant.
.COMPLETE SPECIFICATION.
Improvements in Sun-dials.
I, JOHN RYDER OLIVER, of No. 25, Gwendwr Road, West Kensington, in the
Administrative County of London, C.M.G. and Major-General, Retired List, late
Royal Artillery, 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 sun dials, and it consists in the com-
bination of an arc or circle upon which the hours are marked and a style of a
special contour. The arc in question is an equatorial one and, in respect of the
relative positions of it and the style, the axis of the latter biscets the centre of, the
former and is perpendicular to its plane. The hours are marked upon the concave
face of the arc (which is of the length necessary for that purpose) and are indicated.
upon it by the passage of the edge of the shadow of the style across an equatorial
line marked upon the said arc.
The contour of this style may be described as the result of the revolution of a

page_text: certain curve about a polar axis. This curve is obtained by setting off along a
straight line in both directions from an equatorial zero, series of abscissæ, and
laying off ordinates at right angles thereto. These abscissæ are found for certain
dates at given intervals by multiplying the length of the radius of the equatorial
arc or circle by the tangent of the sun's declination for the particular date in
question. The ordinates are found by multiplying the same radius by the sine of
the angular value of the equation of time. The curve is then drawn through the
series of points so found.
Perfect accuracy demands the use of two distinct styles, one for use from the
winter to the summer solstice, and the other for the following and equal term.
But if a single style of mean contour be used, the error produced is so minute that
it is practically inappreciable. The style may be furnished with a flange or be
marked to show which side of the shadow is to used.
The sun dial-constructed as above described indicates true local mean time, but
the hour arc may be set to indicate time according to any standard meridian
required.
In order that my invention and the best means of carrying it into practical effect
as well as of using it successfully may be thoroughly understood I will now describe
it and them in detaii, referring in so doing to the accompanying figures which are
to be taken as part of this Specification and read therewith.
Figure 1 is a side elevation of an improved sun dial constructed according to my
invention.
Figure 2 is a front elevation corresponding therewith.
a is the base of the instrument. It is preferably rectangular in shape to facilitate
its being placed in the necessary position for the instrument to act properly.
6 is a vertical pillar fast to the base, the two constituting the stand of the
instrument. The sides of the pillar are shewn as parallel with the sides of the
base. The necessary position for it to occupy is one due north and south.
c is a latitude arc and d is the style which is supported between the ends of
the said are in the relative positions already specified. Provision for setting the
axis of the style at an angle with the horizontal plane equal to the latitude of
the spot where the dial is to be used, is made as follows. e, f are a pair of cheeks.
These are attached to the pillar 6 in such a way as will allow of a little play
on each side of the latter. The upper portions of their opposite faces are cut
with grooves of the same radius as the latitude arc, and these form a slot in 3
which the latter rest steadily in the vertical plane or can be moved therein about
the centre of the circle of which it is an arc. 9 is a concentric groove in one side
of the latitude arc, and g', g' are two guiding pius. h is a screwed pin. One end
of it is fixed fast in the cheek f. It passes through the other cheek e and carries,
on the projecting end, a milled head i. Screwing the latter along the pin in the 4
direction of the cheek holds the two cheeks rigidly to the sides of the pillar, and
the latitude arc between them. The latter is graduated right and left from
its centre-the graduations are not shewn in the drawings-and a vertical line ; is
set out on the cheek to prevent error in the setting of the arc.
f
The small end of the style must point to the north, and for use in the northern 4
hemisphere, it will be uppermost, i.e., in the position illustrated in the figures.
The instrument is set for use south of the equator by putting the thick end
uppermost.
The contour of the style and how it is to be obtained has been already specified.
k is an equatorial or hour are divided, say, to spaces of 5 minutes.
5
Four times a year, the equation of time vanishes, and at those times the style
would intersect its own axis. To allow for the necessary thickness of the rod
carrying the style, a slight adjustment of the hour arc must be made at each time.
Provision is made for effecting such adjustment as follows. The arc k lies in a
groove cut across the latitude arc in which it is held in the desired position by a 5
pair of clamps 1, 1, one on each side of it. m, m' are two marks upon the arc k, and
the latter is to be clamped with one of them coinciding with the edge of the clamp.

page_text: The left hand or west mark m is used from about the 15th of April to the 21st of
June, and from about the 25th of August to the 21st of December. At other
times, the 12 o'clock line must coincide with the right hand or east mark m². When
the said line coincides with the mark m (looking north), the left hand edge of the
shadow d' is the one which indicates the time. When the right hand mark is used,
the right hand edge of the shadow is the indicating edge. Thus, the 12 o'clock line
must be shifted from one mark to the other four times a year, viz., about April 15th,
June 21st, August 25th and December 21st. It is not of any consequence if the
adjustments are not made exactly on the dates specified.
I do not confine myself to the exact details specified above for guiding the
adjustment of the hour arc but may vary them. For instance, the marks m, m' may
be upon the clamp, and the 12 o'clock line be used in combination with them instead
of the edge of the clamp.
The local mean time is shewn by the point at which the indicating edge of the
shadow d' intersects the central line on the hour arc. Thus the time by the dial
illustrated in Figure 2 is 2.25 p.m. on some day between April 15th and June 21st
or between August 25th and December 21st, or it may be 2.36 p.m. on some day
outside these limiting dates.
If the instrument is wanted to indicate a certain standard time instead of local
mean time, the hour are is shifted through the arc corresponding to the difference
of longitude.
Thus if it is in Dublin, and London time is wanted, the 12 o'clock mark is moved
24 minutes to the west, because Dublin is 24 minutes west of London.
The dial can always be set with the latitude arc in the plane of the meridan by
means of a watch which gives true local time.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be carried into practical effect, I declare
that what I claim is :-
1. In a dial, a style of the contour ascertained as hereinbefore set forth.
2. The combination of style as claimed in the preceding claim and an adjustable
latitude arc.
3. The combination of style of a contour ascertained as hereinbefore set forth and
an hour arc adjustable transversely of the latitude arc.
4. The general construction of my improvement in sun dials as hereinbefore set
forth with reference to the accompanying drawings.
Dated this 3rd day of October 1892.
PHILLIPS & LEIGH,
No. 22, Southampton Buildings, Chancery Lane, London, W.C.,
Agents for the Applicant.