Solar Radiometer keyring Shadow box dimensions: 20 x

Shadow box dimensions: 20 x 18 x 3

Inside are a set of metal vanes which are mounted on a spindle

Stone measures 8mm across at widest point

This is a 2nd edition print of an original watercolor painting -- any imperfections

Heat and water resistant

Solar Radiometer keyring Shadow box dimensions: 20 xInvented in 1873 by chemist & experimenter Sir William Crookes, the solar radiometer was the first way in which man could demonstrate light as an energy source. The radiometer consists of an airtight glass bulb, containing a partial vacuum. Inside are a set of metal vanes which are mounted on a spindle. When exposed to sunlight, artificial light, or infrared radiation, the vanes turn with no apparent motive power, the dark sides retreating from the