[4] In 1734 Caleb Smith invented a "sea quadrant" using an unsilvered glass mirror to reflect the image of the sun into the telescope.
Ayres produced an instrument based on this design mounted on gimbals over a magnetic compass, with a spirit level for use when the horizon was not visible, the whole contained in a solid wooden case.
[citation needed] Around 1750 Ayres invented and made a sailors' arithmetical instrument, now held in the University Museum of Utrecht.
It consisted of a brass disk on which a number of circular logarithmic scales were inscribed, with two radial wires that could each be locked to a point on the circumference.
[6] A brass mariner's compass in gimbals set in a mahogany box, made by Ayres in Amsterdam around 1775, is said to have been the property of Sir Isaac Newton.