Small orrery on mahogany stand by Benjamin Martin, England, mid-18th century. The orrery shows seven planets (to Uranus), but Uranus is thought to be a later addition.

Dated to the middle of the eighteenth century, this miniature planetary model was made by the instrument maker Benjamin Martin. Called an orrery or planetarium, it is a demonstration device to show the motions of the Earth, Moon and planets around the Sun. Orreries became popular during the 17th century, especially after Sir Isaac Newton published his universal theory of gravity. To reproduce the motions of the solar system this model employs a hand crank to drive gear wheels.

This orrery has a brass calendar base with a wooden pedestal stand and seven planets out to Uranus on rod-arms. However, close examination of the gearwork suggests that Uranus was added later, and that the orrery would originally have only shown six planets out to Saturn. Although it is generally understood that Uranus was ‘discovered’ by astronomer William Herschel in 1781, Herschel originally thought he had seen a comet. It was only during 1782 that the new discovery was designated a planet. Since Martin died in January 1782, he would not have lived to see the acceptance of the solar system’s new planet, and thus we would not expect his orreries to show it.

Martin had built a reputation making instruments and lecturing in the south and west of England before moving to London in 1756. His shop on Fleet Street was known for being particularly well stocked. At a time when many scientific instruments – especially intricate demonstration instruments such as orreries – were expensive, he was particularly keen to make devices affordable to those with more limited means. This small orrery is constructed on a simplified pattern and would have been cheaper than larger, more ornate instruments.

For further information, see:

J. R. Millburn, ‘Benjamin Martin and the Development of the Orrery’, British Journal for the History of Science vol 6 issue 4, 1973