Monocular Compound Microscope and Eyepiece, by Andrew Ross, London, Mid-19th Century

This copper alloy instrument stands on trunnions on a flat tripod foot. The limb has a square cross section and a cylindrical post extending below the limb carries the plano-concave mirror on a sliding sleeve. A rack and pinion mechanism set at the rear of the instrument raises a cylindrical post from within the limb. An arm, inscribed with the maker's name, is attached to the top of the post and the body tube screws into a threaded hole at the end of the arm. The eyepiece consists of two lenses set in two tubes that screw together. This assembly pushes into the top of the body. A double mill-edged knob near the lower end of the body operates the fine focus. A cylinder that protrudes from the lower end of the body is mounted of a spring so it can move several millimetres back into the body. It has an external thread to take objectives. The mechanical stage has a square stage plate with a sliding bracket to support slides and a pinhole for accessories. A rotating disk with three apertures is mounted on the underside of the stage.