Valerie Hodgkinson

The field covered by David Brewster in his, "Treatise on Optics', first published in 1831, is quite extraordinary in its extensive grasp and lucidity of presentation ahead of the understanding of optics by his European peers. From my personal interest, the book underpins the whole optical basis of the field of science known as gemmology. Perhaps the greatest revelation was the discovery of the Brewster angle of reflected light, by which the refractive index of a material (transparent or opaque) can be measured. Of equal import was his understanding of polarised light