Pair of coloured glas discs, 1760.

These glas discs were used by Dr Stephen Demainbray (1710-1782), science lecturer and private astronomer to King George III, in his lectures on colour. Demainbray toured Britain and France between 1749 and 1754, giving public lectures on natural philosophy. In 1754, he became one of the many scientists advertising courses of lectures in London. In lecturing on the topic of colour, he was able to glorify Isaac Newton's (1642-1727) theories on the spectrum, and treat the theories of his rivals 'in a candid manner'.