Round-bottomed glass eudiometer. The top end carries a small hollow brass cylinder with slits and three radiating pointed rods. A glass cylinder, in a brass mount graduated from 0 to 100, is attached to the brass cylinder. A swiveling brass ring is fastened to the top. The instrument bears the inscription "Euderometro Fontanian Made by Martin London." It was built by the famous English natural philosopher Benjamin Martin, presumably around 1780. It is a reconstruction of Felice Fontana's eudiometer, of which no specimens survive. The eudiometer was used to measure the quantity of carbon dioxide in atmospheric air within a confined space.