Polarising Microscope, by C. D. Ahrens, London

The instrument consists of a round copper alloy pillar which is hollow fastened to the mid point of one side of a triangular base. The maker's name is inscribed on the base. At the top of the pillar is a copper alloy arm with a copper alloy ring, having a scale in degrees from 0 to180 in one degree increments around the circumference away from the pillar. The collar fits an eyepiece, which consists of an eye lens and a Nicol prism fastened inside a copper alloy cylinder. The prism is set in cork and is held in place by a piece of paper that relates the instrument to the Post Master at Bury St. Edmunds. Below this on copper alloy arms are two sets of condenser lenses again mounted in copper alloy and free to rotate out of the optical axis of the instrument. There is a loose sleeve on the pillar above a fixed arm which carries the prism in a long cylindrical copper alloy mounting. At the base of the instrument is a copper alloy collar holding a concave mirror in a copper alloy setting on a horseshoe mount.