The microscope has been modified in various ways for specialized applications. The inverted chemical microscope, made from 1850 into the 1900s has a microscope tube mounted at an angle below the stage where a prism transfers light from the fluid or other object of study resting on an open unobstructed stage through an objective under the stage. The petrographic microscope, which was commercialised in 1838 for mineral identification and petrographic studies, is fitted with a sub-stage light polarizer and a polarizing analyser filter in the tube above the objective so the user can control the polarization of light transmitted through a transparent thin section of mineral or rock specimens for identification. Dissecting microscopes are simple microscopes with lenses on a rotating arm mounted to a stand and specimen stage. Metallographic microscopes are designed for examination of opaque metals and large forgings while in a lathe. The photo-micrographic apparatus is a microscope that can be turned to a horizontal position along a rail (optical bench) mounted with a bellows camera at one end. Horizontal refracting microscopes have been manufactured primarily for clinical use, and some microscopes from the mid-1800s are convertible from horizontal to vertical. The panoticon is a nineteenth century dual microscope/telescope with interchangeable barrels for either application. The ‘Davon’ is a dual telescope-microscope in which the objective lens of the telescope focuses in front of a microscope objective attached to the end of the eyepiece tube, which can be unscrewed for use as a microscope. The solar microscope is designed to project the image of a transparent object on a microscope slide by using sunlight.