IMPROVEMENTS IN COMPASS CORRECTORS
Year: 1871

page_text: PROVISIONAL SPECIFICATION left by Thomas Bassnett at the Office
of the Commissioners of Patents, with his Petition, on the 17th
July 1871.
I, THOMAS BASSNETT, of Liverpool, in the County of Lancaster,
Nautical Instrument Manufacturer, do hereby declare the nature of
the said Invention for "IMPROVEMENTS IN COMPASS CORRECTORS," to be
as follows (that is to say) :—
This Invention has for its object the production of a simple instrument
whereby any deviation in the magnetic compass may be discovered
without calculation, as the deviation may be at once read off from the
instrument.
An instrument constructed according to this Invention may consist
of an ordinary compass card on an axis springing from the centre of the
top of a horizontal bar or beam supported on gimbles and kept hori-
zontal by means of a weight suspended on the lower end of a rigid
pendent lever springing from the under side of the said horizontal bar

page_text: or beam, the ends of which are turned up at right angles thereto so as
to form standards to which is pivoted a rectangular frame, to one axis
of which is pivoted a loose pendant pointer on the face of a dial attached
to the side of the frame, having a graduated scale marked thereon for
indicating the latitude. The reverse pivot of the frame is provided with
a set screw for adjusting the frame and holding it in position. One of
the other bars of the frame is fitted in the centre of its length with a
dial graduated from the apex to the right and left in six parts, and
sub-dividing it into hours and parts of an hour so as to indicate the time
before and after the meridian. Above and in the centre of the compass
card is pivoted a horizontal transverse bar, the ends which are open and
the extreme inner sides of which holes are each provided with a fine
projection forming pointers, by which to read off the degrees of sun's
bearing from the graduated scale on the edge of the compass card.
Between the holes in the end of the pointer bar is mounted a vertical
semicircular dial plate graduated so as to give the altitude, and to the
radius point of this semicircle is attached by a pivot, universal or other
joint, a lever which extends beyond the arch and is connected to a
semicircular bar, on which a declination scale is marked jointed to the
radius points of the dial marked with the time index and the opposite
bar from the spring of the declination bar extends an index pointer
which travel over the faces of the time dials by which the instrument
is set, as will be hereafter explained. The lever which works over the
face of the declination arch on the centre of the transverse horizontal
bar or beams above the compass card carries on its head a stile or sight
attached thereto by a swiveling joint that the sight picce may always
lie at the same angle in relation to the arch or otherwise, which is
arranged to travel and can be held in any position on the arch bar by a
set screw or its mechanical equivalent. The arched bar may be formed
with a scale for indicating the angle of the sight or stile.
Care must be taken in constructing the instrument that the joints of
the arched bar, the centre lever carrying the time and latitude are all
pivoted in one plain.
To ascertain the deviation of the compass, if any, all that is required
is to move the arched bar until the pointer come to the time of day,
then move the centre lever carrying the stile or sight on the arched bar
to the angle of declination, and elevate the rectangular frame untill the

page_text: pointer corresponds with the latitude of place of observation, when the
sun's fine bearing can be at once read off from the scale on the edge of
the compass card.