Compound microscope signed J. D. V. Fokkenberg Fecit Utrecht 1777; rack adjustment to both body and stage, on large wood base; metal of speculum mirror badly tarnished; one single lens o.g., 2-lens ocular

This microscope is engraved on the body tube and is of great interest in that it is provided with rack-and-pinion adjustment for the body and for the stage, a combination that is rarely found in a microscope, and especially one so early in date.

The pinions are fixed and the racks move, carrying the body and the stage. The body is very firmly attached both at the top and the bottom of the slider, as is provided with 'aquatic' movement which allows of its covering a considerable area of the large stage.

The optical system consists of a single-lens objective and an eyepiece of the Huygenian form. The objective has a focal length of 1/5in., the field-lens of the eyepiece a focal length of 2 3/4in. and the eye-lens a focal length of 1 3/8in. The field-lens is 5 1/2in. from the objective and 1in. from the eye-lens.