Optical model of a spectrum with inverted colours, maker unknwon, 1752. Once belonged to Stephen Demainbray. A handwritten inscription on the base reads: 'Prism screen & convex lens/Colours inverted '4''.

This model is one of a series of optical models that were once owned by Stephen Demainbray and used by him in his lectures on natural philosophy. it is the most complex of the series and consists of a pinhole in wood with a prism, a convex lens, a second pinhole at the focus of the lens, and a screen. Originally silk cords would have been used to represent the rays of light. Demainbray worked as superintendent at the King's observatory at Kew from 1768 and his collection of instruments and apparatus was absorbed into the King's own collection.