AN APPARATUS, MACHINERY, OR INSTRUMENTS, ON CONSTRUCTION. FOR THE PURPOSE OF TAKING OBSERVATIONS AND ALTITUDES, BOTH BY SEA AND LAND, WITHOUT ANY DEPENDANCE ON THE VISIBLE OR SENSIBLE HORIZON
Year: 1796

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME; we, EDWARD
Cook, of the Town of Falmouth, in the County of Cornwall, Painter, and
RICHARD EVA, of the same place, Watchmaker, send greeting.
WHEREAS His most Excellent Majesty King George the Third did, by
His Letters Patent under the Great Seal of Great Britain, bearing date
at Westminster, the Ninth day of February, in the thirty-sixth year of His
reign, give and grant unto us, the said Edward Cook and Richard Eva, His
especial licence that we, the said Edward Cook and Richard Eva, during the
term of years therein mentioned, should and lawfully might use, exercise,
and vend, within England, Wales, and the Town of Berwick-upon-Tweed,
our Invention of "AN APPARATUS, MACHINERY, OR INSTRUMENTS, ON
CONSTRUCTION. FOR THE PURPOSE OF TAKING OBSERVATIONS AND ALTITUDES, BOTH
BY SEA AND LAND, WITHOUT ANY DEPENDANCE ON THE VISIBLE OR SENSIBLE
HORIZON "in which said Letters Patent there is contained a proviso obliging
us, the said Edward Cook and Richard Eva, by an instrument in writing
under our hands and seals, to cause a particular description of the nature of
our said Invention, and in what manner the same is to be performed, to bu
inrolled in His Majesty's High Court of Chancery within one calendar
month after the date of the said recited Letters Patent, as in and by the
same (relation being thereunto had) may more fully and at large appear.

page_text: NOW KNOW YE, that in compliance with the said proviso, we the said
Edward Cook, and Richard Eva, do hereby declare that our said Invention
is described in the l'lan and description thereof hereunto annexed, and in
manner following (that is to say) :-
No. 1, an Instrument for Taking the Latitude or any Altitude, either by Sca
or Land, without any dependance on the Sensible or Visible Horizon.―This
instrument is circular, and may be made of wood, bone, iron, or steel, or any
other metal, or what is commonly called Clay's Patent Paper, or any other
material that may be suitable for the purpose. Towards the outermost part is
a circular groove covered with glass, or so much of it only as is necessary; the
other part may be covered with wood or any other suitable material, or a cir-
cular glass tube may be fixed in; the groove is to be half filledwith quicksilver,
or any other suitable fluid. A line being drawn across the body or centre of
the instrument will be exactly parallel to the plane of the horizon; the
groove or tube, being exactly half filled with quicksilver or other fluid, each
end thereof must meet the horizon or parallel line, and, consequently, must
give the true horizon. But a principal and most material part in the con-
struction of this instrument is the method contrived for fixing or stopping at
pleasure, either partially or totally, the motion of the quicksilver or fluid.
This is done bymeans of what I call a stopcock, through which the quicksilver
or other fluid passes, and is performed with the greatest case instantaneously,
so that, as soon as an observation is taken, the quicksilver or fluid is fixed or
totally stopped. This instrument also consists of a quadrant, or quarter of a
circle graduated into ninety degrees, and each degree subdivided into three
equal parts. This graduated scale may be either within or without the groove
or tube. An index, moving on a pin from the centre, passes or extends over
the groove or tube that contains thequicksilver or fluid,and also to the scale of
90 degrees, which has a Nonius answering to the subdivided degrees. Through
that part of the index that passes over the groove or tube that contains the
fluid is an opening or hole about an inch more or less diameter, so that the
quicksilver or other fluid may be distinctly seen with a small wire immc-
diately crossing the centre of the opening or hole, so that when an observation
is taken, and the quicksilver or other fluid being fixed, or its motion entirely
stopped by means of the stopcock, the index must be moved so as to bring
the wire or hair that crosses the hole in the index in contact with that end of
the quicksilver or other fluid that passes along by the scale of degrees. When
quicksilver is made use of in this instrument, a small steel ball that will pass
freely through the groove or tube is to float on each end of it, which will press
down the ball, thereby to distinguish more accurately when the wire cuts or

page_text: crosses the end of the quicksilver. On that side of the instrument on which
is the scale of degrees is a sight vane, a small hole being in it, which is placed
exactly parallel to the horizon line, through which hole the observator is
to look. Opposite the sight vane, on the other or opposite side or edge of
the instrument, is what we call the object vane, through which is an opening
or hole about an inch more or less diameter, through the centre of which
opening or hole is a small wire, silk, or hair, or three of either, so that the
centre one may be exactly parallel to the horizon line. When an observation
is taken the object is to be viewed through this opening or hole, and the wire
or hair that crosses its centre, being exactly parallel to the horizon line, is to
ascertain its altitude. Between the object and sight vanes, or rather, as near
as can be conveniently to the sight vane, is placed three, more or less, glasses,
brown or green, or both, or any others that may be most convenient for the
defence of the eye, to be used as occasion may require. On each side the
object vane, on the edge of the instrument, are two brass hooks, that is, on
either side, one for holding a piece of pasteboard or thick paper to be used
only occasionally, or according to the brightness of the sun or clearness of the
weather. But this would not be found inconvenient in the least degree at any
time in taking the sun's altitude. This pasteboard or paper may be made in
the form of a semicircle, with a hole through it opposite the hole in the object
vane, and care must be taken that the hole in the pasteboard or paper is
sufficiently large so as that no part of it may cover any part of the hole or
opening in the object vane.
On the same centre is
No. 2, an Instrument for Taking the Latitude or Altitudes by Sea or Land,
without any dependance on the Sensible or Visible Horizon. This instrument
consists of a circle, one half of which is divided into eighteen equal parts,
which, if subdivided into degrees, would make 180. This circle is placed on
a pin in the centre of a graduated arch of 40 degrees.
an index which is pendulous; this moves on the arch of 40, but only 30 of
these degrees are used with this index. The other 10 degrees, which extends
from the farther leg of the instrument, has a small index which moves out
from behind that leg. The pendulous index has a speculum on its centre,
always parallel to the plane of the horizon when the index is at liberty. A
piece of brass moving on joints across the instrument by means of two springs
either fixes or lets at liberty the index. The thumb of the left hand being
brought to touch the upper part of this brass, the index is left at liberty, but
on taking off the thumb it is fixed as soon as the observation is taken. This
pendulous index has its vibratory motion entirely corrected by means of a
brass friction wheel or roller on the back part of the lower end, which moves

page_text: on the inside of the arch, which, being made perfectly circular, it is so con-
trived as that though it prevents the vibratory motion of the index, yet does
not prevent but rather helps its always falling to its centre. By this instrument
an observation may be taken also with the horizon when visible, and that
easily and accurately. For this purpose there is a wire on the upper part of
the brass frame that holds the defensive glasses which might otherwise be
fixed on the centre of the horizontal speculum. To take an observation in
this way the circle must be screwed fast at 90 degrees on each side the nearer
leg, then look through the sight vane and see the horizon wire before men-
tioned in a direct line with the horizon, then work the observation in every
respect as with a Hadley's quadrant. This instrument may also be made with
one large semicircle instead of the smaller circle in the former description.
The radius of this semicircle to be nearly the same as the arch of 30 degrees,
and may be made to slide thereon. The radius of this being larger than the
whole circle, the degrees may be ascertained more accurately, but is in all
other respects constructed on the same principles with the former, and must
be considered as the same.
In witness whereof, we, the said Edward Cook and Richard Eva, liave
Master Extra in Chancery.
J
SPRANGER.
EDWARD COOK. (L.S.)
RICH EVA. (L.S.)
AND BE IT REMEMBERED. that on the same Fifth day of March, in the
year above written, the said Edward Cook, and on the Eighth day of the
same March, the said Richard Eva, severally came before our Lord the King
in His Chancery, and acknowledged the Specification aforesaid, and all and
every thing therein contained, in form above written. And also the Specifi-
cation aforesaid was stamped according to the tenor of the Statute in that
Inrolled the Ninth day of March, in the year above mentioned.