Specimens showing results of a process, for polishing marbles etc, invented by A. Gath of Rome about the year 1825, and applied to reflectors for astronomical purposes: a) Reflector of Nero Antico b) Piece of sililian jasper agate c) Piece of green granite Erbetta d) Similar piece polished according to the old process by Frattoddi e) Disc of eleven agates as used for polishing a small reflector