Sir David Brewster, Scottish physicist, c 1860s.
© Science Museum / Science & Society Picture Library
Brewster (1781-1868) played a leading part in the popularisation of science in Britain in the 19th century and is chiefly remembered for his lifelong investigations into optics. In 1816 he invented the kaleidoscope and later improved Sir Charles Wheatstone's (1802-1875) stereoscope by introducing refracting lenses. In 1818 he was awarded the Rumford gold and silver medals for his discoveries on the polarisation of light, and from 1859 he was the principal of Edinburgh University. He played a central role in the founding of the British Asociation for the Advancement of Science.