4. Double pillar. Simple monocular microscope. c.1860.

Although from an unknown manufacturer, it is a typically French model called «double pillar».

This simple monocular microscope from unknown manufacturer has a square cast iron base. Two brass pillars screwed to the base that allow tilt movements of the tube. It is moved on a rack with a single micrometric screw. It has a single lens, simple condenser, and a sprocket with three different fixed apertures.

A magnifying glass or «bull’s eye» condenser is attached to the optical tube. It is an additional lighting system, by means of a front lens that condenses the rays, illuminating the object to be observed in an incident way. The magnifying glass has multiple movements by means of two articulated arms on spheres.