IMPROVEMENTS IN INSTRUMENTS FOR TAKING ALTITUDES, LEVELS, AND ANGLES, WHICH I DESIGNATE COLBY'S ALTIMETER, OR SELF-ADJUSTING QUADRANT OR SEXTANT."
Year: 1854

page_text: LETTERS PATENT to Hall Colby, of the City and State of New York,
United States of America, for the Invention of "IMPROVEMENTS IN
INSTRUMENTS FOR TAKING ALTITUDES, LEVELS, AND ANGLES, WHICH I
DESIGNATE COLBY'S ALTIMETER, OR SELF-ADJUSTING QUADRANT OR SEXTANT."
PROVISIONAL SPECIFICATION left by the said Hall Colby at the Office
of the Commissioners of Patents, with his Petition, on the 30th May
1854.
I, HALL COLBY, of the City and State of New York, United States of
America, do hereby declare the nature of the said Invention for "IMPROVE-
MENTS IN INSTRUMENTS FOR TAKING ALTITUDES, LEVELS, AND ANGLES, WHICH HE
DESIGNATES COLBY'S ALTIMETER, OR SELF-ADJUSTING QUADRANT OR SEXTANT,'" to be
as follows:-
The nature of my improvement consists in so contriving and arranging my
altimeter, that it shall always present to the operator a perfect horizontal line
and an exact vertical point, whatever may be the direction and position of the
telescope or glass to which it is attached.
The instrument consists of a brass meridian or circle, shown at A in the
Drawings, divided into degrees and other subdivisions, as at A, together with a
central plate B, moving freely upon a central point.
This central plate B is placed within the meridian A, and is self-adjusting
to the plane of its meridian or horizon. To this central plate are attached
points or indexes a, a, a', placed on its cardinal divisions, and which shew the
position of this plate B in respect to the meridian or circle A.

page_text: This plate B, being self-adjusting, maintains its natural and proper position,
the points a, a, being horizontal, and the point a' being vertical, whatever may
be the direction given the telescope to observe any planet or body; and the
vertical point or index a' determines the angle of the telescope in respect to
the altitude of any such planet or body.
These parts, the meridian and the central plate with its indexes, being
attached to a telescope, enable the observer to obtain in a moment's time the
correct altitude or depression of any planet or body above or below the
horizon.
This instrument is intended for taking altitudes and levels in the place of
many other instruments used for such purposes, and it is believed that it
will perform these operations in a much more simple and correct manner,
as it preserves of its own nature a perfect horizon under all circum-
stances.
•
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Hall Colby in the Great Seal Patent Office on tho 30th
November 1854.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, HALL
COLBY, of the City and State of New York, United States of America, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Thirtieth day of May, A.D. 1854, in the 17th year
of Her reign, for Herself, Her heirs and successors, did give and grant
unto me, the said Hall Colby, Her special license that I, the said Hall
Colby, my executors, administrators, and assigns, or such others as I, the
said Hall Colby, my exccutors, administrators, and assigns, should at any
timo agree with, and no others, from time to time and at all times there-
after during the term therein expressed, should and lawfully might make;
use, exercise, & vend, within the United Kingdom of Great Britain and
Ireland, the Channel Islands, and Isle of Man, an Invention for "IMPROVE-
·MENTS IN INSTRUMENTS FOR TAKING ALTITUDES, LEVELS, & ANGLES, WHICH HE
DESIGNATES COLBY'S ALTIMETER, OR SELF-ADJUSTING QUADRANT OR SEXTART," upon
the condition (amongst others) that I, the said Hall Colby, by an instrument
in writing under my hand and seal, should particularly declare & ascertain
the nature of the said Invention, and in what manner the same was to be
performed, & cause the same to be filed in the Great Seal Patent Office

page_text: within six calendar months next & immediately after the date of the said
Letters Patent.
NOW KNOW YE, that I, the said Hall Colby, do hereby declare the nature
of my said Invention, & in what manner the same is to be performed, to bo
particularly described and ascertained in & by the following statement, reference
being had to the accompanying Drawing & to the letters of reference marked
thereon, making a part of this Specification.
The object of my Invention is to produce an improved instrument for
taking altitudes, angles, & levels, to be used in the place of many other
instruments used for such purposes, and which will perform these duties in a
more simple and correct manner and with more certainty and quickness.
The nature of my Invention or improvement consists in so contriving and
constructing my altimeter, that it shall at all times and under all circumstances
present and secure to the observer an exact and perfect horizontal line and
vertical point, whatever may be the position & direction of the telescope or
glass to which it is attached.
The instrument consists of a meridian A, made of brass or any other metal or
suitable material, graduated as at a', a', to such subdivisions as may be desired,
and a self-adjusting central plate B, with a lock C, to fasten and retain, the
plate B where necessary.
The central plate B is placed between the two outer cases of the instrument
(of which the meridian A is one), and moves freely upon its centre, which is
also the centre of the instrument, and is so constructed as to be self-adjusting,
and so as to secure and maintain at all times a perfect zenith and horizon to
the altitude of observation. To these zenith and horizon points are attached
finely graduated verniers b, b', which traverse through the opening D in the
plate A, & upon the graduated arc a', a', showing the position of the plate A
to the plate B; the plate B being self-adjusting preserves its natural position,
the point 6 being vertical and the point b' being on the horizon, and thus
giving a perfect zenith & horizon to the observer, whatever may be the.
direction given to the telescope in making an observation; and the point b
marks upon the meridian A the angle of the telescope, and determines the
altitude of the object.
The plate B is made, as shewn in Figure 3, of thin plate brass, with a
lip upon its lower edge, to serve as a sort of protection to the weight II,
which being placed or suspended upon one side of the plate B, and con-
sequently rendering one side much heavier than the other, keeps this plate
as a natural effect in one position, and thus secures a horizontal line and also
a true zenith point. As before stated, the plato B moves upon its centre f

page_text: and is naturally kept in one & the same position by means of the weight II,
placed on but one side of this plate; but in order to more effectually secure
and preserve this position, and at the same time give greater steadiness
to the plate B, and prevent and counteract any tendency to great or sudden
vibration which might affect in any degree its correctness or convenience, the
weight H does not move upon the common centre f, but has its own individual
point of support 9 below the centre f, but in the same line with the vernier
or point 6 and the centre f. By this arrangement and contrivance, the whole
weight and effect of the mass II is to keep the vernier or point 6 exactly
vertical as respects the centre f, and consequently the point b' always at the
horizon, while at the same time the weight II moves freely on its own point of
support, and does not interfere in the least degree with the plate B keeping its
natural position; and indeed as the position of the telescope may be altered,
it will be only the weight II which will have much motion, while the plate B
will remain stationary and receive but a slight trenior. In order still further
to secure perfect and steady motion to the weight H, a standard J of thin
brass is attached to the lip of the plate A, and extends upward sufficiently
far to furnish a bearing for the support g, the other bearing being the plate A.
To assist still further free action in the weight H and prevent friction, I insert
a strip of brass in each side of H, & which are the only points of support of
the weight H upon the support g.
To one side of the instrument is fixed a lock C, c, protected by the guard G,
which acts against the edge of the plate B and upon the weight H, &
securely holds them and prevents them from moving, or which, when held
back by the catch c, allows to them free and unimpeded motion. When the
instrument is to be used in taking an observation, the lever C is to be held back
by the catch c, and the plate B thus allowed free motion to adjust itself in its
natural position; but at the moment the glass is brought upon the object, the
observer with his finger moves the catch c, and the lock C immediately acts
upon B and H, and holds them in their then position, and the observer can s
take off the angle at leisure.
Figure 1 is a view of the front plate or meridian A, showing the graduated
are a', a'; the groove or opening D, with the verniers b', 6', attached to the plate
B, and the lock C, c, and guard G. F is the central point of support on which
the plate B moves.
Figure 2 shows the back plate of the instrument and the telescope, and the
handle E, by which the altimeter is held.
Figure 3 is a view of the plate B, with the general shape and manner of
suspending the weight H.
3

page_text: This instrument is particularly valuable for the purposes of navigation, &
is particularly intended and designed for such uses, but it may be rendered very
valuable for land engineering and surveying.
What I claim as my Invention, and desire to secure by Letters Patent, is,
the contrivance and arrangement, whether made in the manner before de-
scribed or in any equivalent manner, of instruments for taking altitudes and
angles at sea or on land, under whatever name they may be called, which are
self-adjusting, and thereby secure and maintain at all times a perfect zenith
& horizon in observations taken for latitude and longitude.
I also claim the lock C, c, above described, or any other equivalent
arrangement of mechanism, by which the central plate B may be instan-
taneously stopped in any position, and thereby also the altitude instantaneously
secured.
HALL COLBY. (L.S.)