Maker's Name: 
Cambridge Instrument Co.
Where made: 
34 × 24 × 17 cm

This pyrometer consists of a telescope with red filter. It is focussed on the source to be tested. The source becomes a background for an internal filament, which is connected to an external battery through a rheostat. The rheostat is adjusted until the filament seems to disappear against the source. The source temperature is read off a calibrated d'Arsonval meter in circuit with the filament.