IMPROVEMENTS IN SOLAR CHRONOMETERS
Year: 1876

page_text: PROVISIONAL SPECIFICATION left by Herbert John Haddan at the Office of
the Commissioners of Patents on the 7th February 1876. A communication
from abroad by Marshal Wheeler, of Big Rapids, Michigan, United States of
America.
HERBERT JOHN HADDAN, of the Firm of Herbert and Company, Patent Agents,
of 67, Strand, in the City of Westminster, Civil Engineer. "IMPROVEMENTS IN
SOLAR CHRONOMETERS." A communication from abroad by Marshal Wheeler, of
Big Rapids, Michigan, United States of America.
My Invention consists in the construction and arrangement of an instrument
which I call a "solar chronometer," having for its object to ascertain time and
latitude by the sun, constructed and arranged as follows:-I form a semicircular
concave plate representing a section of the earth (if the same were a hollow
spherical shell) cut on parallel lines on each side of the equator, a distance equal to
the sun's apparent maximum declination, the same being 23° 27' 24". The ends
of the semicircle are connected to a plate representing the earth's equatorial
diameter, and in the centre of this plate is a hole for the sun to shine through, so
that when the instrument is in use an image of the sun will be cast between the
hours of, say, 7 a.m. and 5 p.m., down upon the inner surface of said semicircle. The
inner or concave surface of the semicircle is laid off with declination lines, one
degree apart, or nearer if desirable to the total amount of 46° 54′ 48″. The
middle line of these graduations would of course occupy the position of and
represent the earth's equator, and there would be 23° 27' 24", each side of it,
equaling the maximum declination of the sun north an south during the year.
At 90° or the mid point of the semicircle I draw a line across said circle at right
angles with the equatorial and declination lines; this line will be the principal
imeridian or 12 o'clock line parallel thereto, and on both sides I lay off hour lines,
fifteen degrees apart minus the amount necessary to allow for the refraction of the
sun's rays in passing through the earth's atmosphere.
Having to use this instrument upon the round surface of the earth it is necessary
to arrange it that its circle may be set parallel to the equator in any latitude; I
accomplish this in a convenient manner by using a bed or horizon plate, at each end
of which I fix an upright ear through which points are fastened, and upon these
points the circle rests and turns. The circle is maintained in any desired position
by means of a hinged connecting rod, oue end of which is attached to the solar
bridge or plate of the circle, and the other to a clamp sliding in a beviled slotted
Price 2d.1

page_text: groove on a latitude bar made to form part of the horizon plate; the latitude bar
is graduated to degrees and parts of a degree, and read to finer subdivisions by a
vernier graduated upon a clamp.
This chronometer is to be used by setting it at noon to the latitude of the placo
by leveling the horizon plate and inclining the circle, so as to bring the sun's image
upon the meridian line at that point where the declination line for the given day
and hour intersects the same, then clamp fast, and the latitude of the place can be
seen on the bar. At that place solar time may be ascertained between the usual
hours, say from 7 a.m. to 5 p.m., at any time by setting the clamp at the
ascertained latitude and bringing the sun's image upon the given declination for
the day and hour, and by using the proper equation the same may be reduced to
clock time.