Repro Scientific Instruments - Orreries All about them

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Orrery small £1700

Orrery large £2225

A selection of beautiful fully working instruments made in the U.K. to the highest specifications by Roy Mallett. Created by Paul Kellar M.B.E. M.A. these 2004 orreries are made combining two of James Ferguson’s designs (circa 1763), which are a working representation of the Earth and Moon system, and include all of the planets known at that time.

An Orrery demonstrates many of the important aspects of the monthly and annual movements of the Earth and Moon. The first was made by George Graham in 1710 for his patron the 4th Earl of Orrery; hence the name. They are also known as a planetarium and listed under the generic heading of scientific instruments in antiques guides.

The Orrery illustrates the constant direction in space of the Earth’s inclined axis of rotation and helps to explain the seasonal variations of sunrise and sunset. The equinoxes and solstices are shown, as is the Sun's annual path through the signs of the Zodiac. It clearly shows the rotation of the moon around the earth, with its changing declination during the lunar month. These movements demonstrate the changing phases of the moon, and explain the corresponding variation in tide times and amplitudes. (Ferguson’s earth/moon gear ratio of 235:19 is the Metonic cycle of 235 lunations in 19 years). The Orrery also demonstrates that an eclipse occurs when the moon is either full (eclipse of the moon) or new (eclipse of the sun) when at the same time the moon is near a node of its inclined orbit. The nodes of the moon’s orbit also rotate, with a period of about 18.7 years, this explains why the possible times for an eclipse move year by year.

James Ferguson was born in Keith, Scotland in 1710, he was a self-taught scientist and astronomer. During 1743 in London he established himself as a successful lecturer and author; publishing books and pamphlets on scientific subjects. He designed several astronomical clocks and orreries, mainly for use in his lectures. He was elected a Fellow of the Royal Society in 1763. He became a friend of Dr. Benjamin Franklin, who was in Britain at that time to lobby Parliament about tax grievances. Ferguson designed a variant of Dr. Franklin’s famous three-wheeled clock for which he received acclaim.

All moving parts; planets, decorative balustrades, ornamental figures (large model), engraved dials and zodiac plaques are manufactured from solid brass. The exception is the solid gem stone blue earth globe ball; (jewel globe: lapis lazuli for oceans, a variety of other semi-precious stones are used for countries, such as: turquoise, or jade, or tigers eye). The base is manufactured from stained American white oak (Quercus alba), a wood that is used extensively in cabinet making.

Both models run electrically. Small model achieves full rotation in a half hour. The large model in 5 minutes. The large model can also be disconnected from the motor and hand turned to see planets, earth and moon rotation at a higher speed for demonstration purposes. Both models may have the planets moved by hand to specific positions.

These superb fully working electrical models represent a breadth of knowledge, talent, and craftsmanship that span the years. They are for those of inquiring and perceptive mind, who love things that have a purpose to their beauty.

Each Orrery is supplied with a signed certificate of authenticity and are individually numbered.