ROSS IMPROVED ACHROMATIC GILLETT CONDENSER (Ross' Improved 4-10^ths Achromatic Condenser)

This condenser is a later and improved version of the Gillett condenser invented in the 1840s and produced by Ross. This condenser has two wheels of apertures and stops (the early Gillett type only had one). This allows each size opening to be used in combination with various stops including central stops (for dark ground illumination), and various openings allowing various kinds of oblique illumination. Unlike the original type, this condenser does not have a correction collar. An improved method of controlling the two disks from underneath the wheels of stops and apertures are the two knurled knobs.