AN IMPROVED QUADRANT FOR TAKING SOLAR ALTI- TUDES FOR LATITUDE WITHOUT AID OF MARINE HORIZON, AND FOR ASCERTAINING THE TRUE LONGITUDE
Year: 1855

page_text: LETTERS PATENT to Thomas Hedgcock, of 7, Cavendish Grove,
Wandsworth Road, in the County of Surrey, Master, Royal Navy,
for the Invention of "AN IMPROVED QUADRANT FOR TAKING SOLAR ALTI-
TUDES FOR LATITUDE WITHOUT AID OF MARINE HORIZON, AND FOR ASCERTAINING
THE TRUE LONGITUDE."
Sealed the 28th September 1855, and dated the 31st March 1855.
PROVISIONAL SPECIFICATION left by the said Thomas Hedgcock at
the Office of the Commissioners of Patents, with his Petition, on the
31st March 1855.
I, THOMAS HEDGCOCK, of 7, Cavendish Grove, Wandsworth Road, in the
County of Surrey, Master, Royal Navy, do hereby declare the nature of the
said Invention for "AN IMPROVED QUADRANT FOR TAKING SOLAR ALTITUDES FOR
LATITUDE WITHOUT AID OF MARINE HORIZON, AND FOR ASCERTAINING THE TRUE
LONGITUDE," to be as follows, viz. :—
Figure 1 is a front elevation of quadrant; Fig. 2 is a back elevation of
the same.
The quadrant is the old frame and arch, with an index bar and glass A; the
horizon glass B, which is half silvered, is the size of the index bar and glass A,
and is in a direct line with it when at 90° on the arc D. On the back part of
the quadrant are fixed two archs E, F, from zero to 120 each way. G is a

page_text: small glass as a detector, by which both latitude and longitude are obtained;
His a spirit level for an approximation to the altitude.
To observe an altitude of the sun at noon, having the supposed meridian
altitude, set the index B to 90° on the arch F, and the index A at zero
and the arch D, and look to the sun or horizon, and put the index A
through the detector G towards the nadir, and the sun's image will be
seen in index glass A;. and turn down detector glass G until they are
parallel, then bring back the index B to zero, and if at zero the sun thus
brought in contact is parallel the altitude is correct, and by looking into the
bubble of level the sun will appear in the centre. To find the longitude, place
the index A at 90° on arch D and the index B at zero, look over index A
towards nadir, and the sun's image will be perceived just that distance from
nadir as its altitude is from the horizon. By bringing the sun's image in
detector G parallel to the sun's image in index B, the two suns are made to
cross each other, neutralizing the sun in B; and by bringing back the index A
to zero and looking over it as before, there will also be seen three suns, and
looking up to the real sun under the index A. through index B there will be
seen the real sun and 3 images: index A one image, and detector G two
images, and they are always equidistant, so that when the quadrant is adjusted
at 90°, as aforesaid, the other sun is at zero, the same as the sun's image in
the two indexes A and B; but the moment any movement of the earth, either
miles or degrees, the detector alters its adjustment equal to the miles or
degrees so altered in the arch index A and D.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Thomas Hedgcock in the Great Seal Patent Office on
the 29th September 1855.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS
HEDGCOCK, of No. 7, Cavendish Grove, Wandsworth Road, in the County of
Surrey, Master, Royal Navy, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Thirty-first day of March, in the year of our Lord
One thousand eight hundred and fifty-five, in the eighteenth year of Her
reign, did, for Herself, Her heirs and successors; give and grant unto me,
the said Thomas Hedgcock, Her special licence that I, the said Thomas
Hedgcock, my executors, administrators, and assigns, or such others as

page_text: I, the said Thomas Hedgcock, 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, exercise, and vend, within the United Kingdom of, Great
Britain and Ireland, the Channel Islands, and Isle of Man, an Invention
for "AN IMPROVED QUADRANT FOR TAKING SOLAR ALTITUDES FOR LATITUDE WITHOUT
AID OF MARINE HORIZON, AND POR ASCERTAINING THE TRUE LONGITUDE," upon the
condition (amongst others) that I, the said Thomas Hedgcock, by an instru-
ment in writing under my hand and seal, 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 Thomas Hedgcock, do hereby declare
the nature of the said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement, that is to say:-..
The accompanying Drawings fully illustrate my Invention, in which Fig. 1
is a front elevation of the quadrant, and Fig. 2 is a back elevation of the
Similar letters of reference indicate corresponding parts in the several
same.
Figures.
The quadrant consists of an angular frame with an arch D, graduated from
zero to 90°, and subdivided, and an index glass and bar A, with vernier
scale A', corresponding with the scale, as in Hadley's sextant. The glass B,
called the horizon glass is half silvered, and equal in size to A. On the
back part of the quadrant are fixed two archs E, F, graduated from 0° to
120° each way. B¹ is an index bar and vernier, and connected to the horizon
glass B., G is a small planum glass as a detector, moving on a central pin
in front of index glass A,, by which both latitude and longitude are obtained.
This glass can be moved to any angle with the glass A. H is a spirit level.
To observe an altitude of the sun for latitude at noon, having the sup-
posed meridian altitude, set the index bar B₁ at zero, put the index A to
the supposed altitude on the arch D, look over the index A to the nadir
point, and the sun's image will be seen in glass B; turn down detector
glass G until the sun's image in glass G is parallel with the sun in glass B,
and if the sun in detector glass G be balanced in the centre of the level H,
then the altitude is correct. The great advantage of the spirit level H in
taking solar altitudes is to test the correctness of the instrumentin the event of
the weather being hazy or foggy..

page_text: Example: Altitude taken at Southampton on the 29th July 1855. When
the supposed meridian altitude for latitude was 57° 30', set index A to 57° 30'
on arch D, and by looking over the index and turning down detector glass, as
above described, I found the two suns parallel in the glass B, as well as the
sun in detector glass G balanced in the centre of the level; consequently 57° 30'
was the true altitude, which taken from 90°, the zenith, leaves 32° 30' the
zenith distance; and add to which 18° 30' north, the declination of the sun for
the day gives 51° the true latitude.
There are other modes of obtaining the altitude for latitude with this instru-
ment as well as the original method for the altitude to the horizon for latitude
in ordinarily fine weather.
To ascertain the longitude, place the index A at 90° on the arch D and the
index B¹ at zero, look over index A towards nadir, and the sun's image will be
perceived just that distance from nadir as its altitude is from the horizon. By
bringing the sun's image in detector glass G (which said glass is at an angle
of 45° to the glass A) parallel to the sun's image in glass B, the two suns are
made to cross each other, neutralizing the sun in glass B; and by bringing
back the index A to zero and looking over it as before there will be seen
three suns; and by looking up to the real sun under the index A through
glass B there will be seen the real sun and three images; in glass A one
image, and in detector G two images, and they are always equidistant, so that
when the quadrant is adjusted at 90°, as aforesaid, the other sun is at zero, the
same as the sun's image in the two glasses A and B. But the moment any
movement on the earth is made, either miles or degrees, the detector alters its
adjustment equal to the miles or degrees so altered on the arch D, index A.
Example: The distance from London to Antwerp is known to be 176 miles.
I adjusted the instrument as above at London, and I found on arriving at
Antwerp a difference of meridian 4° 30', which according to the mean lati-
tude between the two places gives a fraction above 39 miles to a degree of
longitude, or 176 miles the distance between London and Antwerp. On the
return journey the instrument was again adjusted, as above, and on arriving at
London the same result was given; thus defining the true meridianal distance
or longitude.
Having thus fully described the nature and application of my Invention,
and in what manner the same is to be performed, I wish it to be understood
that I do not claim as new the form of the quadrant, the arch D, the index
bar and glass A, with vernier scale A', nor the horizon glass B; but what I
do claim as my Invention, and desire to secure by Letters Patent, is,―
First, the detector glass G; the two archs E, F,-which are fixed to the back

page_text: of the quadrant and graduated from 0° to 120° each way; the index bar and
vernier scale B', which is connected to the horizon glass B; the spirit level for
ascertaining the correctness of an altitude as well as in foggy and hazy weather,
all (in combination with the parts I do not claim as new) for the purpose
of obtaining in the manner herein described the true latitude and longitude.
And, second, the position of the horizon glass B, and its moving principle
for the like purpose.
In witness whereof, I, the said Thomas Hedgcock, have hereunto set my
hand and seal, this Twenty-fourth day of September, in the year of
our Lord One thousand eight hundred and fifty-five.
THOMAS HEDGCOCK. (L.B.)