Signed: SMITH, BECK & BECK. LONDON 4639

Case 40 x 15 x 17 cm

This excellent instrument is in the group classified as "Third-class microscopes" and is an example of "The Binocular Popular Microscope", as illustrated in R. Beck A Treatise (1865). It has a triangular base with a raised perfored bar in the centre for varying the inclination of the body tube. A pillar is hinged to the base at the back by two screws in the post, and is also hinged to the tubular limb.
In the lowest end of the limb there is a peg fitting the perforations on the bar. The mirror has gimbals and is connected by an arm to a sliding case. On the upper part of the limb there is a triangular bar with rack and a double milled-head pinion for coarse focus, and the fine focus is by a micrometer long lever fine adjustment atop. An arm fixed to the upper limb supports the Wenham binocular tube, with interocular distance variable by rackwork. On the circular stage fits a plate and upon it the slide carrier, beneath the stage there is a cylindrical fitting for the reception of additional apparatus. The plain stage can be taken off and replaced by a stage with mechanical movements by two milled heads, which are placed on the same spindle.
Rackwork controls the position of the condenser (with an iris diaphragm and signed R & J. BECK LTD), which carries a movable arm for glass filters (one turquoise, one blue and one opaque white) and metal discs to modify the light beam.