An Apparatus for Teaching Mine-gas Testing.

摘要

106,225. Lewis, L. H. Oct. 21, 1916. Teaching mine-gas testing.- In apparatus for teaching minegas testing, pictures of gas caps corresponding to various percentages of gas are colourprinted on a strip of paper mounted on rollers in a cardboard casing. The pictures of the gas caps are brought separately in front of the display aperture of the casing by operating the projecting ends a, a' of the rollers.