Optical model of a spectrum brought to a focus, 1753.
© Science Museum / Science & Society Picture Library
Dr Stephen Demainbray (1710-1782), a science lecturer of the time, devised these 'optical machines' as poor weather often prevented experiments on sunlight. They represented experiments on the spectrum of sunlight using prisms. In each the light, represented by a thread which is now mising, entered through a wooden pinhole, and was split into colours by the prism. The models show different experiments with the coloured rays.