IMPROVEMENTS IN COMPASS CORRECTORE
Year: 1882

page_text: LETTERS PATENT to John Jordan Wilson, of Sunderland, in the County of
Durham, Compass Maker, for an Invention of "IMPROVEMENTS IN COMPASS
CORRECTORE"
PROVISIONAL SPECIFICATION left by the said John Jordan Wilson at the
Office of the Commissioners of Patents on the 25th February 1882.
JOHN JORDAN WILSON of Sunderland in the County of Durham Compass
Maker. "IMPROVEMENTS IN COMPASS CORRECTORS."
Compass correctors made according to this invention are simple in construction
and easier in the mode of application and also give more accurate results than
those heretofore in use. I make the dial or inner or central movable dumb card
with an outer movable graduated ring. The dumb card and the ring both work
in an outer gimballed weighted ring upon which the words "Ships Head" is
marked with an index line By means of a central clamping screw both the
dumb card and the graduated ring can be fixed in position relatively to the
gimballed ring and relatively to each other. The dumb card is marked to quarter
points similar to an ordinary compass card excepting that the "points of the
compass are placed on opposite sides in roverse position to that of an ordinary
compass that is the E is placed where the W is ordinarily and so on. The movable
ring is graduated along the inner edge from north to 180° both ways, and the
outer edge is graduated from the line of the aforesaid 180° thirty or forty degrees
right and left to indicate easterly and westerly variation; at 90° or thereabouts
on the easterly variation side P.M is marked, and on the opposite side A.M. is
marked; thus when the South point of the dumb card is upon 180° of the movable
graduated ring then P.M will be on the east side and AM on the west side of
this reversed dial.
In the centre of the dial is mounted a movable sight vane having a slit in the
upright part and a fine wire stretched between the latter and the point of the
vane; the sight has a black centre line on white ground in continuation of the
slit and reaching to the point of the sight The instrument is enclosed in a case
of brass or wood: it is arranged to work with "Burdwoods" or other tables and
to be used with the sun or with a star or with a distant object. It is available
for making a true course and a magnetic course. In order to facilitate the instant
use of the instrument I may employ a central dial or graduated part in connection
with a hand or index and with clock work for moving same once in four and
twenty hours and thus do away with the necessity for setting the instrument
according to the hour.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Jordan Wilson in the Great Seal Patent Office on the
25th August 1882.
JOHN JORDAN WILSON of Sunderland in the County of Durham Compass
Maker "IMPROVEMENTS IN COMPASS CORRECTORS."
Compass correctors made according to this invention are simple in construction
and easier in the mode of application and also give more accurate results than those
heretofore in use.
Figure 1 of the accompanying drawings is a side elevation, Figure 2 a plan and
Figure 3 a vertical cross section of a compass corrector made according to the first
part of this invention.
I make the dial or inner or central movable dumb card A with an outer movable
graduated ring B. The dumb card A and the ring B both work in an outer
gimballed weighted ring C upon which the words "Ships Head" is marked with
an index line at a. By means of a central clamping screw and nut D both the
dumb card A. and the graduated ring B can be fixed in position relatively to the
gimballed ring C and relatively to each other. The dumb card A. is marked to
quarter points similar to an ordinary compass card excepting that the "points, of the
compass" are as here shown preferably placed on opposite sides in reverse position
to that of an ordinary compass that is the E is placed where the W is ordinarily
and so on. The movable ring B is graduated along the inner edge from north to
180° both ways, and the outer edge is graduated from the line of the aforesaid 180°
thirty or forty degrees right and left (as here shown 30°) to indicate easterly and
westerly variation; at 90° or thereabouts on the easterly variation side PM is
marked, and on the opposite side AM is marked; thus when the South point of
the dumb card is upon 180° of the movable graduated ring then P M will be on
the east side and A M on the west side of the reversed dial.
In the centre of the dial is mounted a movable sight vane having a slit in the
upright part, and a fine wire stretched between the latter and the point of the
vano; the sight has a black centre line on white ground in continuation of the slit
and reaching to the point of the sight. It will be observed that the drawing
Figure 2 shows the zero of the dumb card A and the movable ring B exactly
opposite each other but this coincidence is only accidental.
The instrument is enclosed in a case E of brass or wood. It is arranged to work
with Burdwood's or other tables and to be used with the sun or with a star or with
a distant object. It is available for making a true course and a magnetic
course.
In order to facilitate the instant use of the compass correctors I may construct
the same with a central dial or graduated part in connection with a hand or index
and with clock work for moving same once in four and twenty hours. Such a
construction is applicable for use with any of the heavenly bodies and I thus do
away with the necessity for constantly setting the instrument according to the
hour.
Figure 4 is a vertical section and Figure 5 a plan of so much of such an
instrument as will be necessary to describe this part of my invention.
The Instrument consists of a clock a having a dial b which is divided into
24 hours and minutes in the usual manner as shewn in the drawing and having
hands 6 and 6 which indicate civil time. The Clockwork also gives motion to a
pointer having at one end a tube d which contains cross wires (or it may be a
sight vane). The pointer c also carries at its centre a white disc e with sight slot

page_text: or mark or instead of this I may mount the disc e at one end of the pointer o and
place in the centre a shadow style or pin, in this case the tube d would be omitted.
At the division 12 and 24 of the clock dial are fastened the two ends of a sector
or half circular ring f which is graduated from 0 to 90° both ways which ring f
may be clamped by means of the screws g in any position relatively to an outer
segment f¹ which is fixed to the interior of the outer case. The pointer c indicates
on a vertical sidereal time ring (outside the clock dial) which is preferably
divided into 24 hours and subdivided into every 5 minutes; outside the sidercal
time ring his the compass dial k which rests on a circular cradle or gimbold
ring carrying pivots m which work in bearings in an outer ring which
latter is again pivotted transversely (best seen at n¹ Figure 5,) on to the
outer case 0. The clock a and dial b are supported by means of an inner
ring p having two arms 21 and p2; fixed at the extremities of these are
two bosses and from which project (for a short distance on each side of
both bosses) grooved slides 8 and s¹ in which the sidereal time ring his free to
move circumferentially, but may be clamped when desired by the screw t which is
provided for the purpose.
The bosses and also form bearings in which pivots u and u¹ projecting on
each side (from the cradle which carries the compass dial) may turn.
In using the instrument with the rim I first wind up and set the clock a to the
local or ship's time, I then set the vertical divided sidereal time ring to the
equation of time and set the outer compass dial k to the variation at place, I then
raise (swinging it on the pivots u and u') the clock dial band consequently the
sidereal time ring h to the sun's altitude and then clamp the whole instrument and
move it round until the shadow of the cross wires in the tube & fall upon the
slotted centre disc e, tho compass dial k will then point out continuously the
magnetic compass course.
To use the instrument for the stars or moon the only alteration in the working is to
set the vertical sidereal time ring to the star's meridian passage. This instrument
is used without any tables.
I declare that I claim:
First In compass correctors making the dumb card with a movable graduated
ring all substantially as described with reference to Figures 1, 2 and 3.
Second In compass correctors the combination of a clock a a pointer c worked
thereby and indicating on an adjustable sidereal time ring h, which is pivotted
relatively to the gimballed compass card, and sector appliance for adjusting position
of clock and parts connected therewith all substantially as described with reference
to Figures 4 and 5.
In witness whereof I the said John Jordan Wilson have hereunto set my hand
and seal this Twentyfourth day of August in the year of our Lord One