Maker, Unknown, probably English.
c. 1890. Movement 5h" x 12" dia. / 11"h x 13" over
hexagonal glazed case.
Clock work driven orrery with Earnshaw type, split bi-metallic chronometer detent
escapement with jeweled potence pivot and driven with chain fusee.
Eight day duration. An additional spring barrel drives the orrery with one year duration.
It also serves to eliminate the backlash that would be present in a
mechanism with so many wheels. Subsidiary dial for
the Bisextile, four year
(leap year) cycle. Outer ring with year calendar and zodiacal indicators.
Orrery with two inner planets, Mercury and Venus with rings to indicate each
planet's orbital inclination to the sun. Also a separate tellurian depicting
the Earth and moon system, with moon phases, the moon's orbital inclination
in relation to the ecliptic represented by a ring around the Earth and a
track for the moon to physically rise and fall with respect to the Earth, an
indicator to show where it rises and sets relative to the surface of the
Earth, below a
subsidiary dial for moon's age and phases. The Earth at correct inclination
with dial ring above divided into two twelve hour sectors illustrated with
Roman numerals rotating with the earth. An apparatus connecting the earth to
the Sun to shows the Sun's zenith and declination around the Earth as well
as lines showing the approximate areas of sunrise and sunset in the Northern hemisphere. The entire mechanism
pirouettes upon its central spindle once per year with indicator hand for
outer silvered ring to indicate the position of the sun in the ecliptic as
well as the date, month and zodiac house. All subsidiary dials engraved and
silvered on skeltonized frame with unique upper and lower plates (not
mirrored) held by nine pillars. Total of 45 wheels within the mechanism.
Here we see a close up of the dial below the Earth/Moon system. It has
the four phases of the moon as well as the 29 divisions and numbers. Notice
the small roller attached to the tube holding the moon. This rides along an
inclined ring above the main star ring, and allows visual representation of
the moon's orbital inclination with respect to the Earth. The moon also
rotates correctly with respect to the Earth. Furthermore one can see the
angled gearing used to turn the earth on its axis and to give the correct
23.5 degree tilt with respect to the Sun.
Here we see a close up of the dial below the Earth/Moon system. It has
the four phases of the moon as well as the 29 divisions and numbers. The
engraver gave us a very cheerful disposition for the moon!
Now a close up of the time dial. The hands have a beautifully chisled
detailed. The hole cutout is for the winding square attached to the chain
fusee used to wind a separate spring barrel to drive the chronometer
escapement for the clock. This has an eight day duration.
This is the leap year dial and is written in Latin. Commune means common.
So we have the three common years with the Bissextile year, again Latin for
the leap year. Note the scalloping of all of the dial edges in the movement
as well as the chiseled dial hand.
The dial has a cutout for the winding arbor of the spring which drives all
of the orrery's complications as well has moving the entire mechanism yearly
around its central axis. This spring has a four year duration.