This Bimetalic Actinograph was designed by the British Meteorological Office & records the shortwave radiation received from the sun & sky on a horizontal surface. Although clearly badged on the front by Munro, the instrument was almost certainly manufactured by Casella Limited as described in detail in their trade catalogue, circa 1960. 
The movement operates using sensitive elements of a blackened bimetallic strip mounted at one end on two shaded strips. The free end of the blackened strip records deflections proportional to the incident radiation. This recording is made on a standard daily rotation clock drum.
The combination of black & shaded strips provides compensation for ambient temperature changes. The element is exposed to the radiation through a hemispherical glass dome mounted in the top of the white painted metal cover.
This particular instrument has never been used & still has the metal ‘top hat’ cover fitted at the factory for protecting the dome in transit. It is therefore in exceptional condition. The cost new in 1960 was £100, equivalent to nearly £3000 today. A quantity of charts in arbitrary units from 0 to 80 will be supplied with this unique instrument. Also included are the original installation and operating instructions by Munro.
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