AN IMPROVED INSTRUMENT OR APPARATUS FOR TAKING ANGLES, AND MEASURING LINES, SURFACES, AND SOLIDS, AND ASCERTAINING THE VARIATION OF THE NEEDLE
Year: 1855

page_text: LETTERS PATENT to Frederick Robert Augustus Glover, of Bury Street,
St. James', in the County of Middlesex, Master of Arts, for the Inven-
tion of "AN IMPROVED INSTRUMENT OR APPARATUS FOR TAKING ANGLES, AND
MEASURING LINES, SURFACES, AND SOLIDS, AND ASCERTAINING THE VARIATION OF
THE NEEDLE."
Sealed the 13th June 1856, and dated the 18th December 1855.
PROVISIONAL SPECIFICATION left by the said Frederick Robert Augustus
Glover at the Office of the Commissioners of Patents, with his Petition,
on the 18th December 1855.
I, FREDERICK ROBERT AUGUSTUS GLOVER, of Bury Street, St. James', in
5 the County of Middlesex, Master of Arts, do hereby declare the nature of
the said Invention for "AN IMPROVED INSTRUMENT OR APPARATUS FOR TAKING
ANGLES, AND MEASURING LINES, SURFACES, AND SOLIDS, AND ASCERTAINING THE
VARIATION OF THE NEEDLE," to be as follows:-
My Invention is an improvement upon a former Invention of "an improved
instrument for the measurement of angles," for which Letters Patent for
England were granted to me, bearing date the Second day of November, One
thousand eight hundred and thirty-nine; and consists in constructing the
said instrument or apparatus with additional lines, divisions, scales, or gradua
tions engraved, marked, or placed thereon, in such position and manner as

page_text: that the required angles may be read or observed by means of the reflector
or reflectors attached to such instrument or apparatus, and the requisite
observations may be made to enable the operator to ascertain the variation
of the needle.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Frederick Robert Augustus Glover in the Great Seal Patent
Office on the 18th June 1856.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, FREDERICK
ROBERT AUGUSTUS GLOVER, of Bury Street, St. James', in the County of
Middlesex, Master of Arts, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Eighteenth day of December, in the year of our
Lord One thousand eight hundred and fifty-five, in the nineteenth year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto
mé, the said Frederick Robert Augustus Glover, Her special licence that
I, the said Frederick Robert Augustus Glover, my executors, adminis-
trators, and assigns, or such others as I, the said Frederick Robert Augustus
Glover, my executors, administrators, and assigns, should at any time agree
with, and no other's, 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
INSTRUMENT OR APPARATUS FOR TAKING ANGLES, AND MEASURING LINES, SURFACES,
AND SOLIDS, AND ASCERTAINING THE VARIATION OF THE NEEDLE," upon the con-
dition (amongst others) that I, the said Frederick Robert Augustus Glover,
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 Frederick Robert Augustus Glover,
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 thereof, that is to say :-.
.:
My Invention is an improvement upon a former Invention of "an improved;

page_text: instrument for the measurement of angles," for which Letters. Patent for
England were granted to me, bearing date the, Second, day of November,
One thousand eight hundred and thirty-nine; and consists in constructing
the said instrument or apparatus with additional, lines, divisions, scales,, or
graduations engraved, marked, or placed, thereon, in such position and
manner as that the required angles may be read or observed by. means of
the reflector or reflectors attached to such instrument or apparatus, and. the
requisite observations may be made to enable the operator to ascertain the
variation of the needle; and further, by a series of graduations, in corre-
spondence with three tangents, formed by the circular hinge and the two sides
of the sector, the calibre of any round object; may be ascertained, from a
needle to a round table, and, the weight and dimensions of cannon balls be
calibred and the values read off by the graduations made to exhibit them:
The manner in which my said Invention is to be performed will; be more
readily described and comprehended by a reference to the Specification. filed
in pursuance of the said Letters Patent, the instrument according to the
present Invention being similar to that lastly described in the said filed Specifi-
cation, and represented in the Drawing accompanying the same, excepting only
so far, as the present improvement is concerned. The, construction of the
instrument. and its uses being therein fully. described, it only remains to
explain in what manner the additional lines, divisions, scales,.or graduations
are to be engraved, marked, or placed upon the instrument to adapt it to the
further use of ascertaining the variation, of the compass.
The accompanying Drawing, represents a general plan of the instrument,
the scales or divisions on the two arms or limbs being omitted, and, also the
mirror or reflector, which stands, upon the disc. By comparing this with
the Drawing accompanying the former Specification, it will be observed. that
the present instrument has engraved thereon the additional divisions or scale;
numbered from 0 to 90 degrees, along, the quadrant A, B, of; the disc, which
adjoins the moveable arm or limb M, the disc itself moving with such arm or
limb (as before) against, the arm or limb N. The quadrant B, C, is divided
the same as
before, and so also is the quadrant A, D; but, the quadrant D, C,
in addition to the divisions and, scale, numbered from 0 to 90 degrees. (as
before) from C to D, but, also engraved, thereon the additional numbering of
the divisions or scale from 90 to 180 degrees from D to C, such. numbering
being in continuation of the quadrant A, D, and being placed upon an, inner
circle for convenience. The mode of employing the instrument for the
purposes intended by the present improvement are as follows: To ascertain
the variation of the needle by a double azimuth observation, the instrument

page_text: must be laid in a horizontal position, and the line F, A, of the sector laid in
the direction of the assumed true north, which will be obtained by the use
of the appended magnetic needle. At any convenient time before 12 o'clock,
say, two hours before 12, or at 10 o'clock, the mirror being erected, and
the ruled line which is scratched or engraved upon it facing the sun, a
shadow will be reflected from this ruled line somewhere on the quadrant A, B,
of the disc of the instrument, which will fall on some graduation, say, for
example, degree 25. At two hours after twelve, or at two o'clock, as indicated
by the same watch by which the previous hour of ten was known, if the
shadow reflected by the ruled line fall upon degree 25 of the quadrant A, D,
if the coincidence be exact, and your 12 o'clock true, your assumed variation
was the true variation. If the shadow fall on degree 25 before two o'clock;
or after it, any number of degrees that intervenes, divided by two, and added
or substracted (as the case may require), to the assumed variation, will give
the true..
It will not be necessary to keep the instrument fixed for the intervening
time; all that is required is to note the degree of incidence of the sun's
ray shown by the reflection of the shadow at the given convenient time,
and again at the proper corresponding time after mid-day to set up the
instrument. In the meantime it may be used at any distance from the place
of first observation, or for other purposes, as, for instance, to take the mid-day
time, or the sun's altitude, or both. The first of these processes indeed is;
strictly speaking, essential to the accurate determination of the variation
of the needle, since an observation made by equal times from the meridian
necessarily involves the true hour of 12 o'clock, and the correction of the
watch by the mid-day observation becomes essential. In order to this, the
instrument is to be set up as described for the previous operation, and
the limbs laid according to the known variation. As the earth moves on its
axis, so will the shadow from the ruled line of the mirror be observed to move
on the disc of the joint of the instrument from west to east, travelling, that is,
in the direction from B to A. As soon as the shadow falls on the flêche at
degree 0 it is 12 o'clock by the sun, and the observer will then note how many
minutes more than or short of two hours it was when he made his first obser-
vation, and correct his time for the second observation accordingly. In the
observation for the variation by equal times, these equal times are to be taken
from the observed sun time, and not from corrected time, that is to say, not
from the time corrected by the equation of time tables, which correction,
though necessary in noting the true time of day, will lead to error if used for
this operation.

page_text: For the purpose of calibreing shot, wire, trees, or any other round
rings whatever, the instrument must be opened so as to touch the object in
three spots; this will bring in contact with the arrow head a graduation, the
reading opposite to which will be the diameter in inches of the article
measured, the arrow head and graduations for such reading being engraved,
marked, or placed upon the back or opposite side of the instrument to that
represented in the Drawing, and above more particularly described.
In witness whereof, I, the said Frederick Robert Augustus Glover, hath
hereunto set my hand and seal, the Twelfth day of June, in the year
of our Lord One thousand eight hundred and fifty-six.
FRED R. A. GLOVER. (L.S.)