IMPROVEMENTS IN APPARATUS FOR CORRECTING AND ADJUSTING COMPASSES
Year: 1877

page_text: LETTERS PATENT to Frederick Frasi, of No. 65, Brewer Street, Woolwich, in
the County of Kent, and WALTER GOODSALL, of No. 26, Pyrland Road,
Highbury, in the County of Middlesex, for the Invention of "IMPROVEMENTS
IN APPARATUS FOR CORRECTING AND ADJUSTING COMPASSES."
aled the 7th August 1877, and dated the 25th May 1877.
PROVISIONAL SPECIFICATION left by the said Frederick Frasi and Walter
Goodsall at the Office of the Commissioners of Patents, on the 25th May
1877:
FREDERICK FRASI, of No. 65, Brewer Street, Woolwich, in the County of Kent,
and WALTER GOODSALL, of No. 26, Pyrland Road, Highbury, in the County of
Middlesex. IMPROVEMENTS IN APPARATUS FOR CORRECTING AND ADJUSTING
COMPASSES."
Our Invention relates to apparatus whereby we are enabled by the observation at
any hour of the sun or other heavenly body to ascertain the true meridian and to
correct and adjust the magnetic needle of a compass accordingly, the said apparatus
being so constructed and arranged in portable form that it can be readily applied to
a compass for the purpose of correcting or adjusting it.
We provide clock work which can be regulated to solar time or siderial time, as
may be required, so that its axis shall make one revolution in 24 hours, and we
mount the case containing the same on a horizontal axis in a frame which is
mounted on a vertical axis, providing a graduated quadrant or arc whereby the
axial line of the clockwork case can be set according to the latitude of the place of
observation so as to be parallel to the earth's axis. On the upper side of the clock-
work we provide an hour dial suitably graduated, and we fix on the clock axis arms
or a frame carrying a pair of styles to shew the line of a shadow cast by the sun
or moon, or a set of mirrors whereby the direction of a ray of light from these or
from a star can be observed.
Having at any hour set the styles or mirrors so as to give the indication of the
shadow or ray, then as the styles or mirrors are carried round by the clockwork at
or nearly at the rate of the heavenly body the line of the shadow or ray remains
constant relatively to them, and consequently at any time while the clock work.

page_text: continues in movement observation can be made with the instrument without
requiring fresh adjustment of direction.
The apparatus being mounted on a vertical axis over or under a compass is turned
round till the zero of the clockface, allowing for equation of time, gives the direction
of the meridian, and thus the amount by which the direction of the compass needle
differs from that of the meridian is determined, and the error of the compass from
variation, deviation, or other causes can thus be determined and allowed for.
Although we have above described the clockwork and its case as being bodily
adjustable to the latitude of the place of observation, it may be readily understood
that the clockwork can be arranged in a fixed position and connected by suitable
gearing to the axis which carries round the styles or mirrors for observation, that
axis being itself adjustable in its inclination so as to suit the latitude of the place of
observation.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Frederick Frasi and Walter Goodsall in the Great Seal Patent Office
on the 23rd November 1877.
FREDERICK FRASI, of No. 65, Brewer Street, Woolwich, in the County of Kent,
and WALTER GOODSALL, of No. 26, Pyrland Road, Highbury, in the County of
Middlesex. "IMPROVEMENTS IN APPARATUS FOR CORRECTING AND ADJUSTING
COMPASSES."
Our Invention relates to apparatus whereby we are enabled by the observation at
any hour of the sun or other heavenly body to ascertain the true meridian and to
correct and adjust the magnetic needle of a compass accordingly, the said apparatus
being so constructed and arranged in portable form that it can be readily applied to
a compass for the purpose of correcting or adjusting it.
We provide clockwork which can be regulated to solar time or siderial time, as
may be required, so that its axis shall make one revolution in 24 hours, and we
mount the case containing the same on a horizontal axis in a frame which is
mounted on a vertical axis, providing a graduated quadrant or arc whereby the
axial line of the clockwork case can be set according to the latitude of the place of
observation so as to be parallel to the earth's axis. On the upper side of the clock-
work we provide an hour dial suitably graduated, and we fix on the clock axis arms
or a frame carrying a pair of styles to shew the line of a shadow cast by the sun or
moon, or a set of mirrors whereby the direction of a ray of light from these or
from a star can be observed.
Having at any hour set the styles or mirrors so as to give the indication of the
shadow or ray, then as the styles or mirrors are carried round by the clockwork at
or nearly at the rate of the heavenly body the line of the shadow or ray remains
constant relatively to them, and consequently at any time, while the clockwork
continues in movement, observation can be made with the instrument without
requiring fresh adjustment of direction.
The apparatus being mounted on a vertical axis over or under a compass, is turned
round till the zero of the clockface, allowing for equation of time, gives the direction
of the meridian, and thus the amount by which the direction of the compass needle

page_text: differs from that of the meridian is determined, and the error of the compass from
variation, deviation, or other causes can thus be determined and allowed for.
Although we have above described the clock work and its case as being bodily adjust-
able to the latitude of the place of observation, it may be readily understood that the
clockwork can be arranged in a fixed position and connected by suitable gearing to
the axis which carries round the styles or mirrors for observation, that axis being
itself adjustable in its inclination so as to suit the latitude of the place of
observation.
THE DRAW
Fig. 1 is a perspective view of an apparatus according to our Invention for
adjusting and correcting compasses, Fig. 2 is a plan and Fig. 3 a side view of the
upper part of the apparatus.
A disc plate A, graduated as a compass, is mounted in gimbals with a weight B to
keep it level; on the vertical axis of the disc A is mounted a framing C, which by a
horizontal axis carries a box D containing the clockwork. To this box is attached
a graduated arc E, to which is applied a stationary index F, whereby the axis of
the box D can be set parallel to the polar axis of the earth at any known latitude.
The upper face of the box D is graduated to hours and minutes, and on it is
mounted a gnomon frame G for observing a line of shadow, or by the use of a mirror
H observing a line of light from a heavenly body, and so determining the meridian
as described above. A modified form of the apparatus is shewn in front view at
Fig. 4 and side view at Fig. 5. In this case the clockwork is in a stationary box
D, and its movement is communicated by bevil gearing K to the gnomon frame G,
which is mounted on a disc plate L adjustable to the latitude by the graduated arc M.
Having thus described the nature of our said Invention, and in what manner the
same is to performed, we claim, the use for correcting and adjusting compasses
of apparatus consisting of a gnomon adjustable to latitude and time, the said
gnomon being moved by clockwork so that at any hour by observing the shadow or
line of light from a heavenly body the meridian can be determined substantially as
herein described.
In witness whereof I, the said Frederick Frasi, have hereunto set my hand and
seal this Sixteenth day of November, in the year of our Lord One thousand eight
hundred and seventy-seven.
FREDERICK FRASI. (L.S.)