standing on a large (9 inches diameter) base, with a tall column supporting body of instrument on an adjustable inclining mount, body constructed in such a way that all of the parts are interchangeable, each section with a silver collar onto which is engraved a scale, where the scales fit the corresponding collar has an engraved arrow to show the degree of rotation, two specimen mounts made of a silver metal are also engraved with a scale around the edge, large silver disks each have a scale engraved around the edge, top mirror is plane black glass and can assume any inclination with respect to the axis of the tube and can rotate around it with a similar mirror at the bottom, mirror at the bottom has both a black glass mirror and a stack of plate glass on the other side, final accessory is a holder for various eyepieces which are engraved 'Quartz perpendicular', 'Quartz Parallel' and 'Bi Quartz a 2 Rotations de Soleil', height when inclined at 45deg 74cm, body length 26cm, base diameter 23cm Jean Baptiste Biot (1774-1862) designed this form of polariscope to demonstrate polarization by reflection discovered by Malus in 1808 before the invention of Nicol prism in 1828. Noël Marie Paymal Lerebours (16 February 1807 – 23 July 1873) was a French optician and daguerreotypist. He formed a partnership with Marc Secretan in 1845, the firm then being known as Lerebours et Secretan. Later polariscopes of this size were made but they used a Nicol prism. The complexity and size of this instrument suggests that it was used at the forefront of research into polarised light and is a rare survivor from an early period.