George Glazer Gallery - Antique Globes - Collecting Tellurians & Orreries

Q: I recently discovered a charming planetary device at an antique shop with a spinning earth and moon by a company named Trippensee. How does that compare to these orreries?
Trippensee Tellurian Click image for full description and enlargement.	A: Trippensee was the leading American manufacturer of tellurians from the early 20th Century, located in Detroit, Michigan. Tellurians don't include all the planets like an orrery does. They're used to demonstrate and teach the relative motion of earth, moon and sun, and help explain the phenomena of day and night, the four seasons, and solar and lunar eclipses. This example is from the early 20th century with a maple arm. It has a brass sphere representing the sun, a 3-inch earth globe, and two wooden spheres -- one representing the moon and the other Venus.
It's driven by driven turning the wooden arm by hand, and has chains that mesh with gears so that the earth spins, and the earth, moon, and Venus revolve. Often a zodiac scale is affixed to the base. Q: How are they used in study? A: Tellurians demonstrate several natural cycles: that the earth spins once a day and revolves around the sun once a year, the moon revolves around the earth once a month, and Venus revolves around the sun at a different rate than the earth.