Radiometer used to illustrate Sir W. Crooke's researches on radiation

Radiometer used to illustrate Sir W. Crooke's researches on the radiation of heat in high vacua (numbered 36A in original listing): contains a semi-cylinder of aluminium with a mica screen, a platinum sprial for heating, and a minute radiometer that can be held by a magnet in any part of the bulb to serve as an indicator; to test the intensity and direction of lines of pressure when a candle is held near the bulb