The two movements are independent and performed manually on the side of the plate opposed to the side on which the mirror is situated by means of a worm that acts on a gear wheel coaxial with the mirror and by means of a gear wheel that acts on the rack edge of the ring.
The plate is fixed to the inside of the window so that the mirror is on the outside and the metal tube from which the light emerges can be screwed to the aperture.
In this way the orthogonal rotating movements of the mirror can be controlled from the inside to direct the beam of light in the desired direction and to compensate, with slight and frequent adjustments, for shifts caused by the apparent movement of the sun.
The section of the beam can be limited by using a circular diaphragm or a slit of miscellaneousable width placed at the extremity of the tube through which the light penetrates.
By unscrewing the outlet tube from the plate, a solar microscope or a polariscope can be screwed into its place; with the former the face of the mirror frame to which is attached a normal sheet of silver-plated glass is used and with the latter the other face which holds a sheet of glass with the back blackened.