A NEW INSTRUMENT FOR TAKING THE ALTITUDE OF THE SUN, TO BE TERMED THE HELYPSOMETER
Year: 1858

page_text: LETTERS PATENT to William Clark, of 53, Chancery Lane, in the County
of Middlesex, Engineer and Patent Agent, for the Invention of "A NEW
INSTRUMENT FOR TAKING THE ALTITUDE OF THE SUN, TO BE TERMED THE
HELYPSOMETER."-A communication.
Sealed the 10th September 1858, and dated the 19th April 1858.
PROVISIONAL SPECIFICATION left by the said William Clark at the
Office of the Commissioners of Patents, with his Petition, on the
19th April 1858.
I, WILLIAM CLARK, of 53, Chancery Lane, in the County of Middlesex,
Engineer and Patent Agent, do hereby declare the nature of the said
Invention for "A NEW INSTRUMENT FOR TAKING THE ALTITUDE OF THE SUN, TO
BE TERMED THE HELYPSOMETER," to be as follows:-
The main object of this Invention is to enable the altitude of the sun to be
taken when the natural horizon is obscured by fog, or otherwise invisible.
The instrument consists of two parts, one of which is employed to record
the altitude by the action of the sun's rays upon a sensitive coating of similar
nature to those employed in photographic or heliographic processes, and the
other to measure the altitude thus recorded. The first-mentioned portion of
the instrument consists of a hollow hemisphere, whose equatorial plane is
kept in a horizontal position, or as nearly so as practicable, and has a small
orifice in the centre, and whose concave is prepared with the sensitive coating.
The rays of the sun, being admitted through the orifice above mentioned,

page_text: produce a mark upon the sensitively prepared concave surface, and by applying
the measuring portion of the instrument to measure the distance in degrees
of a circle from the equatorial plane of the hemisphere, the altitude is obtained,
being represented by the said distance in degrees. The instrument is repre-
sented in the accompanying Drawing.
Fig. 1 represents an elevation of the instrument, partly in section, in a
condition to receive the impression of the sun's rays, to record or mark the
altitude.
Fig. 2 is also an elevation of the instrument, partly in section, representing
it with the measuring portion applied to measure the altitude as recorded by
the sun's rays on the sensitively prepared surface. Similar letters of reference
indicate corresponding parts in both Figures.
A is a hemispherical bowl of brass or other metal, having its interior con-
cave surface plated or otherwise lined with silver, and having a rebate a turned
or otherwise formed around the interior of the rim to receive a circular plate
B, which is fitted accurately therein and secured by buttons g, g, attached to
the bowl; the interior surface of the bowl A, and the upper plane surface of
the plate B, combine to form a true hemisphere. The bowl A is suspended
by a gimbal D from the upper part of a frame or stand C, which may be of
wood, and has attached to and below its bottom a stem E, to the lower part
of which are attached four arms b, b, radiating at ninety degrees apart, and
parallel with the plate B; and on these arms are cut screw threads, in which
are screwed four weights c, c, which are capable of being screwed nearer to or
further from the stem, to bring the surface of the plate B, which may be
termed the horizon plate, in or parallel with the plane of the horizon, which
condition is indicated by spirit levels d, d, secured to said plate; e is the
central. orifice of the horizontal plate B, through which the sun's rays are
admitted to act upon the sensitive coating of the concave of the hemisphere.
This orifice e should be very small, and the plate B should be countersunk on
the under side to make a sharp margin to said orifice, so that said orifice
may be exactly in the equatorial plane of the hemisphere; f is a small plate
pivotted to plate B to cover the orifice e, to shut out the light from the interior
of the hemisphere, to protect the sensitive covering from the action of light
when the instrument is not in use.
To record. the altitude of the sun upon the concave of the hemisphere, it
is only necessary to place the instrument in the condition shown in the Figures,
in a position in which it is exposed to the sun's rays when the sun shines
brightly enough to cast a shadow, and to then uncover the orifice e to admit
the rays to the interior of the hemisphere to act upon the sensitive coating of

page_text: the concave, on which they produce a spot or streak according to the length
of time the orifice e is left uncovered; the distance of said spot or streak
from the surface of the horizon plate B or edge of the bowl, measured along
the concave of the hemisphere in degrees of a circle, gives the altitude of the
sun. To take a meridian altitude, the instrument is placed in the sun's rays,
and the orifice uncovered shortly before it is supposed to be noon, and left so
till a short time after it is supposed to be noon. By this means a streak is
produced upon the sensitive preparation, the lowest part of which corresponds
with the sun's greatest or meridian altitude.
The part of the instrument for measuring the distance of the spot or streak
produced on the sensitively prepared concave surface of the hemisphere
consists in a circular plate G, of a diameter equal to or slightly less than that
of the concave hemisphere, and graduated all round one of its faces, or on the
upper half thereof in degrees, or degrees and fractional parts thereof. This
plate has a radial pivot i, which is fitted to a bearing h in the bottom of the
bowl A, the axis of which bearing coincides with the vertical axis of the
hemisphere when the surface of the plate B is horizontal, the graduated plane
surface of the said plate G being so arranged as to coincide with the axis of
the pivot i, so that when the said pivot is in the bearing h, the said plane will
bisect the hemisphere, and the pivot being provided with a shoulder k, which
supports it on the bottom of the bowl, so that the centre of plate G will be in
the plane of the hemisphere. The plate G is also provided with open segment
formed stays p, p, which fit to the rebate a to keep the graduated plane of the
plate in position relatively to the hemisphere. The plate G is fitted with a
bar H, which is attached to a pivot j to the centre of said plate, and is capable
of turning on said pivot. The said bar H has an index or graduated piece /
secured rigidly to one extremity, and a vernier n and an adjusting screw mat
the opposite end, the "zero" point of said vernier, considered relatively to the
diameter of plate G, being directly opposite the index or "zero" point of 7;
and said bar has attached to it a magnifying glass I, occupying an oblique
position to enable the point of the index or "zero" of the piece l, and the
spot or streak on the concave of the hemisphere to be seen clearly when the
plate G is attached to the instrument to facilitate the adjustment of said index
or piece to said spot or streak. The measuring portion of the instrument
being then applied in the manner represented in Fig. 2, the index or "zero
point at is brought opposite to the spot or streak on the concave, and the
angle read off by the vernier on the graduated circle or arc of the plate G,
whose graduations are inscribed from zero to ninety degrees, commencing at
the horizontal line, as shown in Fig. 2, is the sun's altitude.
"

page_text: As on board a ship or other vessel at sea there is almost always some
motion, the streak produced on the concave when the instrument is used at sea
will be wider than the orifice e, and hence it will be necessary to measure the
altitude by the upper and lower margins of the spot or streak, then add the
two altitudes together, and divide by two, which gives the correct altitude of
the sun's centre.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Clark in the Great Seal Patent Office on the
16th October 1858.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
CLARK, of 53, Chancery Lane, in the County of Middlesex, Engineer and
Patent Agent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Nineteenth day of April, in the year of our Lord One
thousand eight hundred and fifty-eight, in the twenty-first year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto I, the
said William Clark, Her special licence that I, the said William Clark,
my executors, administrators, and assigns, or such others as I, the said
William Clark, my executors, administrators, and assigns, should at any time
agree with, and no others, from time to time and at all times thereafter
during the term therein expressed, should and lawfully might make, use, exer-
cise, and vend, within the United Kingdom of Great Britain and Ireland, the
Channel Islands, and Isle of Man, an Invention for "A NEW INSTRUMENT
FOR TAKING THE ALTITUDE OF THE SUN, TO BE TERMED THE HELYPSOMETER," upon
the condition (amongst others) that I, the said William Clark, my executors
or administrators, by an instrument in writing under my, or their, or one
of their hands and seals, should particularly describe and ascertain the nature
of the said Invention, and in what manner the same was to be performed,
and cause the same to be filed in the Great Seal Patent Office within six
calendar months next and immediately after the date of the said Letters
Patent.
NOW KNOW YE, that I, the said William Clark, do hereby declare the
nature of the said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement, reference being had, to the Sheet of Drawings hereunto annexed,
and to the letters and figures marked thereon, that is to say:-

page_text: The main object of this Invention is to enable the altitude of the sun to be
taken when the natural horizon is obscured by fog, or otherwise invisible.
The instrument consists of two parts, one of which is employed to record the
altitude by the action of the sun's rays upon a sensitive coating of similar
nature to those employed in photographic or heliographic processes, and the
other to measure the altitude thus recorded. The first-mentioned portion of
the instrnment consists of a hollow hemisphere, whose equatorial plane is kept
in a horizontal position, or as nearly so as practicable, and has a small orifice
in the centre, and whose concave surface is prepared with the sensitive
coating. The rays of the sun, being admitted through the orifice above
mentioned, produce a mark upon the sensitively prepared concave surface,
and by applying the measuring portion of the instrument to measure the
distance in degrees of a circle from the equatorial plane of the hemisphere,
the altitude is obtained, being represented by the said distance in degrees,
The instrument is represented in the accompanying Drawing which forms part
of this Specification.
In said Drawing, Fig. 1 represents an elevation of the instrument, partly
in section, in a condition to receive the impression of the sun's rays to record
or mark the altitude; Fig. 2 is a plan corresponding with Fig. 1; Fig. 3 is
an elevation of the instrument, partly in section, representing it with the
measuring portion applied to measure the altitude, as recorded by the sun's rays
on the sensitively prepared surface; Fig. 4 is a plan corresponding with
Fig. 3.
Similar letters of reference indicate corresponding parts in the
several Figures.
A is a hemispherical bowl of brass or other metal, having its interior
concave surface plated or otherwise lined with silver, and having a rebate a
turned or otherwise formed around the interior of the rim to receive a
circular plate B, which is fitted accurately therein, and secured by buttons
attached to the bowl. The interior surface of the bowl A, and the upper
plane surface of the plate B, combine to form a true hemisphere. The bowl
A is suspended by a gimbal D from the upper part of the frame or stand C,
which may be of wood, and it has attached to and below its bottom a stem E,
to the lower part of which are attached four arms b, b, radiating at ninety
degrees apart, and parallel with the plate B; and on these arms are cut screw
threads, in which are screwed four weights c, c, which are capable of being
screwed nearer to or further from the stem, to bring the surface of the plate
B, which may be termed the horizon plate, in or parallel with the plane of the
horizon, which condition is indicated by spirit levels d, d, secured to said
plate; e (Figs. 1 & 2) is the central orifice of the horizontal plate B, through

page_text: which the rays are admitted to act upon the sensitive coating of the concave
of the hemisphere. This orifice e should be very small, and the plate B should
be countersunk on the other side to make a sharp margin to said orifice, so
that said orifice may be exactly in the equatorial plane of the hemisphere; f is
a slide attached to plate B to cover the orifice e, to shut out the light from
the interior of the hemisphere, to protect the sensitive covering from the
action of the light when the instrument is not in use. The concave of the
hemisphere, viz. the interior surface of the bowl A, is polished, and has the
sensitive preparation applied in any suitable manner, and by carefully keeping
the orifice e closed at all times but when an altitude is being taken, the pre-
paration may be made to last a very considerable time; and in many, if not
in most instances, when the instrument is to be used at sea, for which use it
is more particularly intended, it will be sufficient to renew said preparation at
the end of every voyage or passage. To record the altitude of the sun upon
the concave of the hemisphere, it is only necessary to place the instrument
in the condition shown in Figs. 1 and 2, in a position in which it is exposed to
the sun's rays when the sun shines brightly enough to cast a shadow, and to
then uncover the orifice e, to admit the rays to the interior of the hemisphere
to act upon the sensitive coating of the concave, on which they produce a spot
or streak according to the length of time the orifice.e is left uncovered; the
distance of said spot or stroke from the surface of the horizon plate B or edge
of the bowl, measured along the concave of the hemisphere or degrees of a
circle, gives the altitude of the sun. To take a meridian altitude, the instru-
ment is placed in the sun's rays, and the orifice uncovered shortly before it is
supposed to be noon, and left so till a short time after it is supposed to be noon.
By this means a streak is produced upon the sensitive preparation, the lowest
part of which corresponds with the sun's greatest or meridian altitude.
The part of the instrument for measuring the distance of the spot or streak
produced on the sensitively prepared concave surface of the hemisphere con-
sists of a circular plate G, of a diameter equal to or slightly less than that of
the concave hemisphere, and graduated all round one of its faces, or on the upper
half thereof in degrees, or degrees and fractional parts thereof. This plate has
a radial pivot i, which is fitted to a bearing h in the bottom of the bowl A, the
axis of which bearing coincides with the vertical axis of the hemisphere when
the surface of the plate B is horizontal, the graduated plane surface of the said
plate G being so arranged as to coincide with the axis of the pivot i, so that
when the said pivot is on the bearing h, the said plane will be bisect the
hemisphere, and the pivot being provided with a shoulder k, which supports it
on the bottom of the bowl, so that the centre of plate G will be in the plane

page_text: of the hemisphere. The plate G is also provided with open segment-formed
stays p, p, which fit to the rebate a to keep the graduated plane of the plate
in position relatively to the hemisphere. The plate G is fitted with a bar H,
which is attached to a pivot to the centre of said plate, and is capable of
turning on said pivot. The said bar has an index or graduating piece v
secured rigidly to one extremity, and a vernier n and adjusting screw m at
the opposite end, the zero point of said vernier, considered relatively to the
diameter of plate G, being directly opposite the index or "zero" point of l;
and said bar has attached to it a magnifying glass I, occupying an oblique
position to enable the point of the index or "zero" of the piece l, and the
spot or streak on the concave of the hemisphere to be seen clearly when the
plate G is attached to the instrument to facilitate the adjustment of said index
or piece to said spot or streak. Before applying the measuring portion of
the instrument just described, the plate B should be removed, but before
doing this the instrument should be taken out of the sun's rays into a place
where there is little light. The measuring portion of the instrument being
then applied in the manner represented in Figs. 3 & 4, the index or "zero"
point at is brought opposite to the spot or streak on the concave; and the
angle read off by the vernier on the graduated circle or arc of the plate G,
whose graduations are inscribed from 0 to ninety degrees, commencing at the
horizontal line, as shown in Fig. 3, is the sun's altitude.
As on board a ship or other vessel at sea there is almost always some
motion, the streak produced on the concave when the instrument is used at sea
will be wider than the orifice e, and hence it will be necessary to measure the
altitude by the upper and lower margins of the spot or streak, then add the
two altitudes together, and divide by two, which gives the correct altitude of
the sun's centre, as whatever vibration of the horizon plate B takes place will
be as much above as below the real horizon. The instrument may be used
many times without repolishing and removing the sensitive preparation, as it
may in successive operations be so placed in relation to the sun, that even if
similar or nearly similar altitudes are taken repeatedly, the marks on the
sensitive coating will come on different parts of the concave. When the
instrument is constructed specially for use on land it need not be suspended
or balanced by pendulous weights, but may be attached to the frame, and
made adjustable therein by screws applied in the same manner as those for
adjusting surveying instruments.
I have stated at the commencement of this Specification that the main
object of this Invention is to find the altitude of the sun when the horizon is
obscured, but I by no means intend to confine its application to that condition,

page_text: as it is obvious that it can be used as well when the horizon. is visible, but it is
under the former condition that it possesses an advantage over the quadrant
and sextant.
Having described the nature of the Invention, and the manner of per-
forming the same, I wish it to be understood that I do not confine myself to
the use of any particular sensitive preparation for the concave surface of the
hemisphere; but what I claim as the Invention to be protected by the herein-
before in part recited Letters Patent is, the hollow hemisphere, having its
concave surface prepared with a sensitive coating, and having an orifice in
the centre of its equatorial plane through which to admit the sun's rays to act
upon the said sensitive coating, substantially as and for the purpose herein set
forth.
And I also clain the graduated plate G with its appendages, combined with
the hollow hemisphere, substantially as described, for the purpose herein
specified.
In witness whereof, I, the said William Clark, have hereunto set my
hand and seal, this Sixteenth day of October, in the year of our
Lord One thousand eight hundred and fifty-eight.
Witness,
W. G. E. SWINNOCK.
W. CLARK. (L.S.)