Theodolite, mid 18th century.

The Duke of Cumberland's theodolite: Benjamin Cole, a prominent London instrument maker, made this theodolite for the Duke of Cumberland, George III's uncle, in the 1740s or 1750s. It bears the Duke's coat of arms. A theodolite is a surveying instrument that measures both horizontal and vertical angles. A new invention in the eighteenth century, the theodolite was not in fact widely used until the nineteenth.