Radiometers and otheoscopes

A collection of radiometers and otheoscopes of varied shapes and sizes. Each comprises a glass cell with a spindle and aluminium vanes attached. In a partial vacuum, the rotor spins when the vanes are exposed to light.

These instruments were designed by Crookes to measure the mechanical effect of radiant energy. Originally intended to illustrate his papers on 'Repulsion resultion from radiation [...]' published in a the Philosophical Transactions of the Royal Society between 1875-78.

Sir William Crookes (1832–1919), British chemist and science journalist was elected a Fellow of the Royal Society in 1863 and served as its President between 1913-1915.