IMPROVEMENTS IN THE CONSTRUCTION OF AN INSTRUMENT FOR TAKING ALTITUDES, ANGLES, CALLED AN IMPROVED ALTIMETER, OR SELF-ADJUSTING QUADRANT
Year: 1855

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 THE
CONSTRUCTION OF AN INSTRUMENT FOR TAKING ALTITUDES, ANGLES, CALLED AN
IMPROVED ALTIMETER, OR SELF-ADJUSTING QUADRANT."
Sealed the 29th January 1856, and dated the 31st July 1855.
PROVISIONAL SPECIFICATION left by the said Hall Colby at the Office
of the Commissioners of Patents, with his Petition, ou the 31st July
1855.
1, HALL COLBY, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN THE CONSTRUCTION OF AN INSTRUMENT FOR TAKING ALTITUDES,
ANGLES, CALLED AN IMPROVED ALTIMETER, OR SELF-ADJUSTING QUADRANT," to be as
follows:-
My improvement consists in making use of half a circle, or 180 degrees, for
taking observations, and having this half circle suspended below the plane of
the telescope or glass to which it is attached, and also in counteracting, in the
manner hereafter described, any tendency to undue oscillation in the self-
adjusting part of the instrument, and in attaching the whole instrument when
desired to a stock similar to a gun stock, to assist in taking more perfectly
correct observations.
The half circle, or semi-meridian, is of brass or any suitable material, gra-
duated to degrees and parts of a degree, and is generally constructed and made
in all important respects similar to the meridian or full circle described in the

page_text: Specification heretofore filed by me in the Great Seal Patent Office, according
to the requirements contained in certain Letters Patent granted me by Her
present Majesty Queen Victoria, for an "altimeter, or self-adjusting quadrant
or sextant," and bearing date the 30th day of May 1854. In connection with
this half meridian there is also a self-adjusting plate, acting in the same
general manner as the self-adjusting plate described in said above referred
to Specification, which also bears double verniers, ninety degrees apart, and
which traverses upon the graduated half circle. The meridian is attached to a
telescope having two or more sets of contractors and cross wires, and the two
verniers are so placed upon the self-adjusting plate in respect to the plane of
the 180 degrees, that when the telescope is on the plane one vernier shall rest
at the 90 degrees (the half meridian is graduated from 0 at the center each
way to 90 degrees) nearest the field of the glass, and the other vernier shall be
at the cypher, or nadir. The plate to which these verniers are attached being
self-adjusting, they of course preserve the same position whatever may be the
direction of the telescope, and, as in the instrument described in the above
referred to Specification, they give the zenith distance and altitude of the object
at the same time upon the graduated semi-meridian, and a lock fastens them
as in that instrument.
To prevent this self-adjusting plate from unduly oscillating from the rolling
of the vessel or any other cause, I make use of the following improved
mechanism or contrivance:-1 attach to the back plate of the instrument and
near the upper and outer sides two springs, similar to watch springs, both of
which are also connected at their other ends by a common standard or stud to
the central self-adjusting plate bearing the double verniers. These springs are
intended to be of the same tension, and their action is therefore equal upon the
central plate, and one unwinds as the other winds up, which takes place when-
ever the direction of the telescope is changed, and thus their natural effect is
to steady the self-adjusting plate, and prevent it from being much affected by
any sudden motion. The standards by which these springs are attached to the
back plate of the instrument go through that plate, and are so contrived that
they can be wound up, and the springs to which they are attached, and thus
the springs may be kept or regulated so as to have equal tension. These springs
also furnish a convenient and reliable way of adjusting the whole instrument,
which is known by the positions of the verniers. The whole instrument can
also be connected with a stock or shank, which may rest against the shoulder,
thus assisting in holding it more steadily, & consequently in obtaining more
exactly correct observations.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, and
of an Order of the Lord Chancellor, filed by the said Hall Colby in the
Great Seal Patent Office on the 21st February 1856.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, HALL
COLBY, of the City and County of New York, United States of America, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the 31st day of July, A.D., in the nineteenth year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said Hall Colby, Efer special license, that 1, the said Hall Colby, my
executors, administrators, and assigns, or such others as T, the said Ilall
Colby, 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 "IMPROVEMENTS IN THE
CONSTRUCTION OF AN INSTRUMENT FOR TAKING ALTITUDES, ANGLES, CALLED AN IM-
PROVED ALTIMETER, OR SELF-ADJUSTING QUADRANT," upon the condition (amongst
others) that I, the said Hall Colby, by an instrument 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 Hall Colby, do hereby declare the
nature of my 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 accompanying Drawings, & to the letters
marked thereon:-
Figure 1 is a view of the front or face of the altimeter as improved, showing
the motion of the double verniers, and the manner of connecting the whole to
the glass or sight tube. Figure 2 shows the form of the central self-adjusting
plate.
My Invention or improvement consists in making use of a half circle, or 180
degrees, instead of a whole circle, upon which the double verniers traverse, and
in making the central self-adjusting plate a quarter circle, or about a quarter,
and in attaching the whole to the under side of the telescope or sight tube
instead of at its side, projecting both above and below, as described in the
Specification of my former Patent, bearing date the 30th day of May 1854.

page_text: The general form of the improved altimeter is shewn by Fig. 1. The half
circle, or semi-diameter A, is of brass, or any suitable material, and is firmly
attached to the glass or telescope B. This is graduated to degrees and parts
of a degree, as necessary; such graduation, however, counting from the nadir
point, which is marked 0 each way to the plane, or 90°. As the nadir and
zenith points are directly opposite each other, it follows that the graduated arc
in the improved altimeter is in effect the same as that used in the original
instrument. Upon this graduated arc traverse the double verniers a, b, which
are attached to the self-adjusting plate C, and which act upon the same prin-
ciple and in the same manner as in the original instrument, except that they
act below instead of above the centre of motion. This arrangement, of placing
the action of the altimeter below the centre D, serves also to steady the motion
or oscillation of the plate C, and prevent any undue vibration. This semi-
meridian with its back plate is fastened below the glass B, as shewn in the
Drawing, and between the two is the self-adjusting plate C. This self-adjusting
plate C is, however, only about a quarter circle, but this is sufficient for the range
of the altimeter, which sweeps from the plane to the zenith. A skeleton form,
as shewn in Fig. 2, is deemed preferable for the plate C, as it renders the whole
lighter and more easily adjustable. The quadrant form of this plate also favors
its easy and correct adjustment, and enables the operator to adjust at any time
his own instrument should it ever become necessary. To the circular edge of
this plate is securely fastened the curved plate or bar c, at either end of which
are the verniers a and b. As these verniers are made exactly 90° apart, and
are a part of the same piece of metal, they can never change position in respect
to each other, but keep always the same. This plate C is rendered self-
adjusting by means of the projecting part d, which extends beyond the point of
support D, and which is weighted, so as when in its natural position that
one vernier a is at the 90°, and the other vernier b at the nadir; and the
semi-meridian A, with the self-adjusting plate C, and its double verniers
a, b, are so placed in respect to the glass B, that when the glass is on
the plane, one vernier shall rest at the 90° nearest the field of the glass,
and the other at the nadir. As these verniers are in fact a part of the
self-adjusting plate C, they of course preserve the same position whatever
may be the direction given to the telescope or glass, and they show upon
the graduated are at the same time both the zenith distance and altitude
of any planet or object. The plate C is rendered self-adjusting by attaching
to the back of that part of this plate marked d a piece of lead or other
heavy metal, which, by being placed one side of a line drawn through the
centre or axle D, has the effect to always keep the plate C in the same posi-

page_text: tion, i. e., one vernier at the zenith and the other on the plane. This weight
will of course have to be of such bulk as to balance the other parts of the plate
C, and keep it naturally in the above-described position, and it is supported on
a pivot o at its upper end, its lower end being fastened by a screw c, moving
in a slot in d, as shewn in the Drawing. If at any time the altimeter gets out
of perfect adjustment, it is only necessary to loosen the screw e, and slightly
vary the position of the adjusting weight, until the instrument is again in per-
fect adjustment, and then tighten this screw, and this can be done by any
ordinarily skillful navigator. As in my original instrument, the self-adjusting
plate with the double verniers is arrested and held in any position it has at the
moment of any observation by means of a spring lock or catch f, which has a
sharp serrated edge acting through the outer edge plate of the altimeter and
against the rim of the plate C.
To ensure still greater steadiness to the action of the instrument, I attach to
the axle D of the self-adjusting plate, and in front of the face plate of the alti-
ineter, two or more arms or braces h and k, shewn by the dotted lines in Fig. 1,
moving with the axle and self-adjusting plate, and fastened with the verniers to
the rim of the plate C; or the verniers with the connecting bar c and these
arms may all be cast solid (and this is deemed preferable), and then fastened
to the self-adjusting plate in the same manner as the verniers are. This
arrangement of armis upon the face of the instrument, and connecting with
the verniers and plate C, I deen most useful and desirable. These arms are
shaped near the axle, similar to the form shewn in the Drawing, that the
screws 1, 2, may not interfere with the action of the plate C by striking against
such arms.
Tension springs, similar to watch springs, attached by one end to the back
plate of the instrument and by the other to the self-adjusting plate, one uncoiling
as the other winds up, have been and may be used to steady the action of the
self-adjusting plate and prevent any undue oscillation; but they are not deemed
necessary, the present form of the instrument and the centre plate counter-
acting any tendency to undue oscillation. When such springs are used, the
standard by which they are attached to the back plate should pass through that
plate to furnish a method of winding the springs and giving them an equal
tension, and by then the instrument may also be adjusted.
The telescope is a plain glass, with two or more contractors and sets of cross
wires, to ensure a more correct observation than when any less number are
made use of. The whole instrument may be attached to a shank or stock like
a gun stock, to be placed against the shoulder for steadying the instrument
while taking an observation; but a simple handle of any convenient form upon

page_text: the back of the instrument is sufficient to enable one to take observations
which will be perfectly reliable.
The principle of the arrangement and construction and action of my
improved altimeter is the same as that of the original instrument, and, as more
particularly declared in my former Patent, consists in the arrangement of
instruments for taking altitudes and angles, which act irrespective of any
horizon, and which are self-adjusting, so as to secure and maintain at all times
a plane and zenith to the observer.
But what I more particularly claim as my Invention in the improved alti-
meter, and desire to have protected by Letters Patent, is, that construction and
arrangement of mechanism, substantially as above described, by which the
altimeter is reduced in size, the self-adjusting plate and the double verniers
caused to act below the glass, and the whole instrument rendered more conve-
nient and reliable; and in combination therewith the use of a spring lock, as
before, to fasten the self-adjusting plate, and the arrangement or connection of
the balancing weight with the plate C, so that the instrument may at any
time be adjusted; this instrument being principally designed and intended for
the uses and purposes of navigation.
In witness whereof, I, the said Hall Colby, have hereunto set my hand
and seal, this Tenth day of January, A.D. 1856.
MALL COLBY.
(L.S.)