Watertown republican. [volume] (Watertown, Wis.) 1860-1906, 1874-09-30
REMARKABLE PIECE OF MA.
CHlNERY.

Heavenly Bodies.
From the Louisville Courier-Journal, 18th.
Prof. John Davis, Of Allegheny City,
| Penn, an amateur astronomer, has
placed on exhibition for few days, in
the parlor of the Public Library, an APP
paratus illustrating the movement Of the
| various bodies connected with the solar
system, which, for accuracy of detail
| and the number of problems practically
solved, far excels any similar invention
ever attempted. It is simply the most
ingenious piece Of mechanism, for the
object in view, in the world. Prof
! Davis has been engaged in it's construc-
ton during the last thirty years of his
life, and it is only within the last month
that it has been completed. The steady,
persistent, and successful effort to per-
feet continuance for illustrating the
motion of the large number of bodies Of
our solar system, in presence Of classes
in our schools. and in presence of large
and popular audiences will, If we mis-
take not, place Mr.. Davishigh up among
the honored scientific inventors and ben
efactors of the day.
The form Mr.. Davis has chosen for
his apparatus is that of an orrery, and he
gives It the name of Planetelles, from
the two words planetes and satelles
The canvas is a circle of thirteen feet in
diameter, and is covered with large let
ters abbreviating the words expressive
Of the chief phenomena of the planets of
the solar system, and the globes in front
Of it work up, in the details of their
movements, to the various physical
points indicated on the circle. The
ground Of the canvas is black, with
which letters are easily reada along dis
lance from the lecturer. On the outer
edge of the canvas the names of the con-
stellations, Aries, Taurus, etc., are
placed. Next within comes Neptune,
and in regular order toward the centre,
Uranus, Saturn, Jupiter, Mars, Earth,
Venus, Mercury and the Sun.
The motions of the bodies are effected
by means of clock work inside of cylin-
der, no larger in diameter than the face
of all ordinary clock, and in length not
more than six inches So that the ap-
paratus, when ready for use, will extend
out not more than three feet from the
wall of room.
We can only mention some of the
principal phenomena Of the planets ex-
empllfied by this remarkable piece of
mechanism
First-The relative velocities of all
the planets and moons of the solar sys-
tenn are accurately given. All the Ell ght
moons of Saturn, the four of Jupiter
and Uranus, and the one of Neptune
and the earth, are in accurate relative
motion around their respective prima-
ries, which, with the other planets, re-
volve with true relative velocities around
the sun. During one revolution of the
earth, for instance, around the sun, Jul
piter makes one-twelfth of revolution,
and Saturn one thirteenth, and so of the
other planets.
Second-Each of the primary planets
moves in an elliptical orbit an effect
produced by an exceedingly ingenious
and, OF course, very simple continuance.
On the canvas the point of the earth s
aphelian distance, for instance, is
marked, and when the earth reaches
that point of its orbit it is seen to be at
its greatest distance from the sun. The
same is true Of the perihelion, and the
same holds good for all the planets.
Third-The axis of each planet is
properly inclined to the plane of it's or
bit, and each axis preserves its parallel
ism during whole revolution round the
sun. In this wonderful effect the plan
etelles shows to the eye the entire cause
of the change Of seasons, and this is
most beautifully accomplished when a
strong light is placed in the center of
the sun-a glass globe-and all other
lights are eXtinguished, for the light
and shade then fall exactly as in nature
Fourth-All the planets involve on
their axes with proper relative veloci-
ties. While the earth turns once for
instance, Jupiter turns two and two
ffths times, Saturn two and two-thirds
times, Mars once, etc.
| Fifth-The passage of the moon
through it's nodes, and its way of falling
back from night to night, and, indeed,
nearly all the connections of our eccen-
trio conapagnora de voyage are entirely
accounted for by this continuance.
S1xth-The apparent backward mo-
ton OF the planets in their orbits, is, OF
course, clearly accounted for, and, in
deed, there is hardly problem of de-
scriptive astronomy not readily compre-
hended and solved by any one through
the aid of this orrery. The six points
we have especially mentioned will sug-
gest to those interested in astronomy a
large number of others that must be
equally well illustrated, since they are
more or less dependent On those emu
merated.
The Planeteles is for the present
placed in the parlor of the Public Lii
brary, and all interested in the subject
should loose no time in the examination
of It's merits. It really has no competi-
tor in the simplicity of it's construction,
adaptation to popular use, and the num-
Der of problems it is made to solve.
Although Professor Davis has worked
upon this apparatus some thirty years,
yet he seems TO be no enthusiast, but
simply a logical believer in the perfec-
ton OF his lifelong labor.
We may with propriety say that this
piece Of mechanism has cost more than
Sc, 900, aside from. the value of the time
OF the inventor; that it is the only one
OF the kind in existence. and this is the