| 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 mode of its inclined orbit. The nodes of the moon's orbit also rotate, with a period of about l8.7 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. The brass plaques, on the large orrery, with engraved zodiac signs are copies of the original drawings by James Ferguson.
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.
This large model runs electrically achieving full rotation in 1 hour but 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 this large and the smaller model may have the planets moved by hand to specific positions. This superb fully working electrical model represents 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, a makers name stamp, and are individually numbered. | |
