He recalled dimly his pleasure as a boy at the vision of the world given him through a bit of similarly shaped glass. ‘I well remember that everything looked coloured, but in what manner I could no longer recollect. I was just then in a room completely white; remembering the Newtonian theory, I expected, as I put the prism to my eye, to find the whole white wall coloured in different hues and to see the light reflected thence into the eye, split into as many coloured lights.