Beneath the stage is an accessory carrier. The lever (arrow) raises or lowers a central tube, in which can be placed apertures or the Nicol polarizer.
Lever for the Oberhauser/Nachet-type substage accessory carrier.
Stage accessories: A & B: Apertures 4 & 7mm diameter; C: Nicol prism for polarized light imaging.
Nicol inserted into the stage carrier.
The substage mirror has two reflecting surfaces: plane and parabolic.
Description of the substage accessory carrier (J. Quekett, 1855. A Practical Treatise on the Use of the Microscope