Physical description

Comprises two calibrated cylinders mounted on a board for measuring inches of water.
Gauges measure air velocity.
Cylinders are of steel with calibrations on aluminium casings.
Flexible tubes are connected to reservoirs at the back of the mounting board, one black rubber the other red plastic.
A reference barometer is mounted at the bottom right hand corner of the backing board.
Reservoirs at the rear are of metal, coloured blue.

Subjects