ABSTRACT
On February 8, 1672, Isaac Newton presented a paper to the Royal Society of London in which he argued principally on the basis of experiments with prisms that the ambient white light of daylight was not elementary but composed rather of a mixture of all the hues in the spectrum. Cohen (1956) assures us that this was one of the most unadorned empirical demonstrations that Newton ever launched, requiring little by way of logical, geometrical, or mathematical reasoning of the kind made so familiar in Newton’s later Principia. The idea came to Newton, so gossipy historians like to tell us, on the basis of observations he made with a prism bought at the Stourbridge Fair in the Spring of 1666 when he was 24, shortly before he quit his quarters in Trinity College because of the threat of the Plague.
