Explanatory notes
… (c) Thermometers, pyrometers, barometers, hygrometers and psychrometers ( heading 90.25 ); (d) Instruments and … consist of a set of lamps, coloured screens, an optical system and a level which indicates in different colours the … for open basins and canals (hydroelectric works, irrigation systems, etc.). To ascertain the content of a gasometer, the …