AN IMPROVED INSTRU- MENT FOR DETERMINING LATITUDE AND LONGITUDE, AND FOR SOLVING PROBLEMS IN NAVIGATION, NAUTICAL ASTRONOMY, AND GEOMETRY
Year: 1864

page_text: PROVISIONAL SPECIFICATION left by John Pitman at the Office of the
Commissioners of Patents, with his Petition, on the 19th November
1864. Partly a communication from Joseph Bordwine, of Addiscombe,
in the County of Surrey.
I, JOHN PITMAN, of Brislington, in the County of Somerset, Gentleman,
do hereby declare the nature of the said Invention for "AN IMPROVED INSTRU-
MENT FOR DETERMINING LATITUDE AND LONGITUDE, AND FOR SOLVING PROBLEMS IN
NAVIGATION, NAUTICAL ASTRONOMY, AND GEOMETRY," to be as follows:-
The instrument consists of a broad flat ring, the edge of which is marked
with a graduated scale, serving as a general support to all the other parts;
round the centre of this ring traverses a straight arm having a nonius at the
right extremity to fix it correctly to the declination of the observed object by
means of the scale graduated on the edge of the flat ring. The same arm
supports a semicircle (marked less altitude), which is graduated from the
centre towards the right extremity, so as to read off a vernier to 15" of
degrees; this is the scale of less altitude. The left half of the semicircle is
graduated on its superior, so as to read from the extremity towards the centre
to 20' of degrees.
Even with the interior edge of the above semicircle is placed another, also
graduated at its centre for declination. On this second semicircle slides a
piece by means of which, and the nonius attached thereto, the pivot of a
traversant quadrant may be exactly adjusted to the declination of the observed

page_text: object. This quadrant marked (greater altitude) is graduated in a similar
manner to the right half of the less altitude semicircle, to which it is connected
by a sliding pin.
A third semicircle is attached to the exterior edge of the flat ring. This is
marked latitude, and reads by means of a vernier to 15" of degrees. Its right
superior is divided in the same manner as the left of the less arc, and marked
meridian.
Perpendicular to the latitude semicircle, and firmly fixed to the flat ring,
stands a fourth (marked.time circle). This is accordingly divided so as to be
read off by verniers to 2 seconds of time.
Detached from the instrument is another semicircle to be applied to it
whenever a true azimuth is required. This is divided to half degrees only.
USE OF THE INSTRUMENT.
1: If the latitude and declination be both of the same denomination, viz.,
both north, or both south, adjust the declination verniers on the upper sides of
their respective scales, that is, towards the parts of those scales most removed
from the time circle. (By the upper half of the instrument is meant that
which contains the latitude scale.) But if the latitude and declination be of
different names, or if of the same name the latitude be less than the declination,
adjust the verniers for declination to the scales nearest to the time circle.
2. Move the semicircle bearing the quadrant until the nonius attached to it
exactly coincides on the time circle with the time elapsed between the observed
altitudes; make it fast.
3. Adjust the verniers on the altitude arcs to the corrected altitudes, then.
work those arcs until the verniers exactly coincide with each other.
And, 4, bring the latitude scale directly over the junction of the altitude
verniers, and there make it fast by means of its clamp against the time
circle.
In this condition the instrument will shew,-
1. The latitude.
2. The time from noon of either observation.
3. The azimuth.
1. For the latitude bring the vernier on this scale. to coincide exactly with
the intersection of the altitude verniers, and it will read off the latitude of the
place of the first or second observation according to. which of the two the
declination and altitude of the other have been reduced.
2. For the horary angle or distance of time from noon of either observation,
the vernier against the time circle on the latitude arc will give to two seconds

page_text: the time from noon of taking the first observation A.M. and the second
observation P.M. Should both denominations have been taken on the same
side of the meridian the time read off on the scale would therefore give the
exact period of taking the second afternoon observation, and the difference
between it and 12 would determine the exact hour of taking the first morning
observation. Should the two altitudes be taken on different sides of the
meridian, then will this arc divide the angle formed by the intersection of the
altitude verniers, and the distance of each observation from noon be obtained
without difficulty. The comparison of this apparent, when reduced to mean
time, with that shewn by a timekeeper at the same instant, will determine the
difference of longitude.
3. For the azimuth, apply the zero end of the detached piece to a degree
on the left extremity of the less altitude are (marked azimuth) corresponding
with the less altitude observed. Move the other end of the same piece until
its graduated edge correspond on the meridian with a degree equal to the
latitude of the place of observation. Then on the azimuth scale will be found
the azimuth at taking the less altitude. This azimuth will be to the east of
the pole if the latitude of the less altitude be A.M. but west of it if P.M.
and this compared with the magnetic bearing taken at the time of observing
the less altitude will give the variation of the compass.
The above has been a case of double altitudes; suppose, now, a single
altitude and the time of observation given. Adjust the less altitude arc for
declination as before, and fix the latitude arc to the time from noon of the
hour of observation, then incline the less altitude arc until the observed
altitude cuts the latitude, and the various results will be got up as above.
If a meridian altitude has been observed, adjust the declination arc to the
declination, and fix the arc bearing, the quadrant, and the latitude arc to any
but the same time on the time circle; then the graduated faces of the greater
altitude arc and the latitude arc being brought in the same plane, the latitude
required will correspond with the given altitude on the quadrant.